The Right Installation For Your Wood Floors . NWFA Guidelins

InstallationInstallation – Wood Subfloor Guidelines – Jobsite Conditions

Proper attention and preparation of the jobsite will ensure successful hardwood flooring installation.

Wood flooring by design is not to be used to strengthen/stiffen a subfloor and will not do so. If movement of the subfloor occurs prior to installation and is not corrected, that same movement will occur after installation is complete.


Part I

Minimum Jobsite Requirements

A. Wood flooring should be one of the last jobs completed on the construction project. Limit foot traffic on finished wood flooring.

B. Evaluate the jobsite for potential problems before installation begins, and before wood flooring is delivered to the jobsite.

C. Installation constitutes acceptance of flooring material, subfloor/substrate, the jobsite itself including the ambient temperature and relative humidity at the time of installation, and all impacting variables that may affect a wood floor. For warranty and/or hold harmless agreements, check with legal counsel.

    1. Exterior surface drainage should direct water away from the building.
    2. Do not deliver wood flooring to the jobsite or install wood flooring until the building is enclosed.
    3. If heating and/or air conditioning is in operating condition, it needs to be operating. If it is not possible for the permanent heating and/or air conditioning system to be operating before, during and after installation, a temporary heating and/or dehumidification system that mimics normal temperature and humidity conditions can enable the installation to proceed until the permanent heating and/or air conditioning system is operating.
    4. Do not deliver wood flooring to the jobsite or install wood flooring until appropriate temperature and humidity conditions have been achieved. Appropriate temperature and humidity conditions are defined as those conditions to be experienced in the building after occupancy.
    5. Do not deliver wood flooring to the jobsite or install wood flooring until all concrete, masonry, plastering, drywall, texturing and painting primer coats are completed.

  1. Basements and crawl spaces must be dry. If power washing is required in the basement, do so before wood flooring is installed and allow subfloor and basement to dry before installing wood flooring.
  2. Crawl space should be a minimum of 18″ (457mm) from ground to underside of joists.
  3. Crawl space earth (or thin concrete slab) should be covered 100 percent by a vapor retarder of black polyethylene (minimum 6 mil) or any recommended puncture-resistant membrane, such as Class C, meeting ASTM D1745. Click on Figure 1-1 to enlarge. Check local codes.

Crawl Space Conditions

  • Where a proper ground covering is in place and when venting is required by local building codes, the crawl space should have perimeter venting equal to a minimum of 1.5 square feet per 100 square feet of crawl space square footage, unless local building codes differ from this specification. Note: Local building codes may differ. Follow local building codes.
  • For crawl spaces without ventilation openings, vapor retarder joints must overlap a minimum of 6 inches and be sealed or taped. The vapor retarder should also extend at least 6 inches up the stem wall and be attached and sealed to the stem wall. Continuously operated mechanical exhaust and perimeter wall insulation or conditioned air supply and insulation must be provided.
  • Note the grade level so that the correct type of flooring and system can be specified for the job. Engineered and floating floors can be appropriate for above-grade, on-grade and below-grade installations. Solid wood flooring can be appropriate for above-grade and on grade installations, but not for below grade installations. If the soil surrounding a structure is 3 inches or more above the floor of any level, consider that level below grade. This includes walk-out basements. In addition, the surrounding soil should be sloped away from the structure. See Figure 1-2.
  • Subfloors (wood or concrete) should be checked by an appropriate method for establishing moisture content. Average subfloor moisture content should be within the range as specified for the product by the product manufacturer. See Moisture Testing. See Figure 1-2.
  • Where the minimum jobsite conditions are present, the flooring can be delivered and stored in the rooms in which it will be installed. See >Acclimation and Conditioning of Wood Flooring.

Part II

Additional Jobsite Conditions for Factory-Finished Flooring

A. All finished wall coverings and painting should be completed. Note: Base and shoe mold may be installed after the flooring installation.

B. After installation, if you choose to protectively cover the floor, cover the floor completely, since some species are light-sensitive and uncovered areas may change color. However, covering a glue-down application may not allow some adhesives to properly cure. Follow the flooring and adhesive manufacturer’s recommendations. Use a covering material with a vapor permeance (perm rating) of 1 perm or more (tested in accordance with ASTM E96) to avoid trapping moisture/vapor on or within the floor. Any covering should be taped, using a lowadhesion tape, to base or shoe moldings. Do not tape to finished flooring. When taping paper or sheets together, tape them to each other, not to the floor. As in all installations, at completion of job, inspect flooring from a standing position.


Part III

Jobsite Checklist

See Appendix M.

 

Installation – Hardwood Flooring Acclimation

One of the most crucial steps to wide plank flooring installation is proper wood acclimation and jobsite conditioning.

Below are guidelines defined by the National Wood Flooring Association for hardwood flooring acclimation.


Part I

GENERAL ACCLIMATION/CONDITIONING GUIDELINES

ACCLIMATION: The process of adjusting (conditioning) the moisture content of wood flooring to the environment in which it is expected to perform.

EQUILIBRIUM MOISTURE CONTENT: The moisture content of wood when in equilibrium with its environment. When wood is neither gaining nor losing moisture, equilibrium moisture content (EMC) has been reached.

STORAGE and CONDITIONS

  1. Do not store wood flooring at the jobsite under uncontrolled environmental conditions. Garages, and exterior patios, for example, are not acceptable areas to store wood flooring.
  2. Ideal interior environmental conditions vary from region to region and jobsite to jobsite. It is the flooring professional’s responsibility to know what the “ideal” climate conditions are and customize the floor around those conditions.
  • Determine what the expected seasonal change of wood moisture content is for your geographical location. For a general view of moisture-content averages by region, SeeAppendix D and Appendix E.
  • Upon delivery, check wood flooring moisture content with a moisture meter to establish a baseline for acclimation. Check the moisture content of multiple boards. A good representative sample is typically 40 boards for every 1,000 square feet of flooring. Calculate what the optimal wood moisture content is (baseline) by dividing the high season and low season. Example: If your region has an expected EMC from a low of 6% to a high of 9%, the baseline MC of the wood would be 7.5%. If wood flooring is delivered and recorded to its baseline MC for the geographical location and proper relative humidity conditions are maintained, no acclimation may be required. If the moisture content of the product received is well outside of the range of optimal moisture content, it will be very difficult to acclimate the product properly without substantial dimensional change, distortion, and structural damage. Example: If the moisture content of the delivered wood is 12% and the optimal range is 6%, excessive shrinkage, bowing, cupping and other physical anomalies would be expected during the acclimation process. The wood flooring should not be accepted.
  • Optimal wood moisture content represents only a base line to begin from and does not represent the final EMC required for the interior environment. Acclimation is often required to customize the moisture content of the wood flooring to the interior environment in which it is expected to perform.

GENERAL

NOTE: Some manufacturers do not require acclimation for certain products prior to installation. If the manufacturer recommends that the wood flooring be acclimated before installation, proceed as follows:

  1. Ensure that the building is enclosed.
  2. Verify that the building is maintained at normal living conditions for temperature and humidity.
  3. Where building codes allow, permanent heating and/or air conditioning systems should be operating at least five days preceding installation to promote proper acclimation and should be maintained during and after installation. For radiant heat, see Appendix H.
  4. If it is not possible for the permanent heating and/or air conditioning system to be operating before, during and after installation, a temporary heating and/or dehumidification system that mimics normal living (occupied) conditions can enable the installation to proceed until the permanent heating and/or air conditioning system is fully operational.
  5. Acclimate the wood flooring as necessary (see Acclimation, Part II below). Note: Not properly acclimating wood flooring may cause excessive expansion, shrinkage, dimensional distortion or structural damage. The worst-case scenario is one in which wood flooring is stored at the jobsite in an uncontrolled environment, then immediately installed. This is especially true when the materials are stored in an area that is subject to excessive moisture and humidity conditions. Acclimation outside of the area in which the wood is to be installed does no good at all; in fact, it is likely harmful to store wood flooring at the jobsite under conditions that don’t reflect expected normal environmental conditions.
  6. Prior to installation, ensure that wood flooring is within acceptable range of moisture content with the wood subfloor. For solid strip flooring (less than 3″ wide), there should be no more than 4 percent moisture content difference between properly acclimated wood flooring and subflooring materials. For wide-width solid flooring (3″ or wider), there should be no more than 2 percent difference in moisture content between properly acclimated wood flooring and subflooring materials.

Part II

ACCLIMATION

Wood flooring is a hygroscopic material subject to dimensional change as a result of variations in moisture, temperature and humidity within the surrounding environment. Wood flooring simply needs to reach moisture content level in equilibrium with the surrounding environment (EMC) in which it will be installed, at or near normal living conditions. The process of reaching this equilibrium is defined as acclimation, which allows the wood to properly adjust itself to the normal living conditions within the structure; that is, the temperature, humidity conditions and moisture content that will typically be experienced once the structure is occupied.

THE PROCESS OF ACCLIMATION

If the manufacturer recommends that the wood flooring be acclimated before installation, proceed as follows:

  1. Acclimation can be facilitated by breaking the floor units into small lots and/or opening the packaging. A common practice is to cross-stack the materials with spacers (¾” to 1″ sticks) between each layer of flooring to allow air circulation on all sides of all boards.
  2. Most recommendations state that the materials need to acclimate from a minimum of 3 days up to no given maximum. While it takes time to acclimate a product, the most important aspect is that the materials reach a moisture content that is in equilibrium with its expected use. Acclimate the materials as long as necessary to accomplish this task, taking the necessary moisture readings to indicate when the materials have reached the proper moisture content and when no further changes occur.
  • For site-finished wood flooring, before installation and before sanding and finishing takes place, allow the flooring to acclimate (settle-in) to the controlled environment, and to stabilize for a period of time. Some flooring professionals suggest 5 to 7 days. Engineered flooring installed using an adhesive application system may require a longer post-installation acclimation period to allow all residual off-gassing to occur prior to application of a finish. Follow adhesive manufacturer’s recommendations.
  • Tropical imported species generally require more time in order to properly acclimate the wood flooring. Some tropical species lose moisture or gain moisture at faster or slower rates than domestic species due to higher overall density, oil and resin content and interlocking cell structure. In addition, the resins and oils make accurate MC readings more difficult. Resistance (pin type) meters require multiple readings of multiple boards in order to arrive at a more accurate average MC reading. Pinless meters that include multiple depth level adjustments may offer faster and more-accurate internal readings.
  • Engineered and solid factory finished flooring follows specific manufacturer’s recommendations and some may not require acclimation. Follow manufacturer’s guidelines to retain all warranty coverage. Warranty coverage generally requires that jobsite conditions be maintained between 30% to 50% relative humidity and that those conditions must be maintained before, during and after installation for the life of the floor. Failure to comply with these manufacturer’s requirements may result in irreversible structural damage and void related warranties.

WOOD’S COMFORT ZONE

  1. As a general rule, with geographic exceptions, wood flooring will perform best when the interior environment is controlled to stay within a relative humidity range of 30 to 50 percent and a temperature range of 60° to 80° Fahrenheit. (In some climates, the ideal humidity range might be higher or lower, 25 to 45 percent or 45 to 65 percent, for example.)
  2. The chart below indicates the moisture content wood will likely have at any given combination of temperature and humidity. Note the equilibrium moisture content in the recommended temperature/humidity range (shaded area) coincides with the 6-to-9 percent range used by most flooring manufacturers during the manufacturing/shipping process. Although some movement can be expected between 6 and 9 percent, wood flooring can shrink or swell more dramatically outside this range. When wood is neither gaining nor losing moisture, equilibrium moisture content (EMC) has been reached.

Equilibrium Moisture Content of Solid Wood Species at Various Temperatures and Relative Humidity Readings Wood flooring has a comfort level too. Wood flooring will perform best when the interior environment is controlled to stay within a relative humidity range of 30% to 50% and a temperature range of 60° to 80° Fahrenheit. Fortunately, that’s about the same comfort range most humans enjoy. The chart below indicates the equilibrium moisture content of wood flooring at various temperatures and humidity conditions. The left column indicates temperature in degrees Fahrenheit and Celsius. The bottom row indicates percent relative humidity. The values in the chart indicate the equilibrium moisture content (EMC) for any given combination of temperature and humidity. For example, at 70° Fahrenheit and 40% relative humidity, the equilibrium moisture content is 7.7%. The shaded area indicates the generally recommended range for wood flooring – 6% – 9% EMC, which occurs when temperature is 60° – 80° Fahrenheit or 15° – 26° Celsius, and 30% – 50% relative humidity.

Moisture Testing for Wood Flooring

Some of the first steps to successful wood flooring installation are the most important.

Here’s some information on moisture guideline testing and vapor retarders.

Reference to ASTM Standard revisions: ASTM Standards listed are most recent revisions or use ASTM Standard in effect at time of installation.


Part I

Moisture Testing for Wood Flooring and Wood Subfloors

Determining moisture content is an essential part of quality control within the flooring installation process. Flooring Installers must know the moisture content of the wood flooring, as well as the subfloor.

A. The most accurate measurement for moisture content in wood is the oven-bake-out method. However, it is not widely used because the cost and difficulty of performing the test on-site is not practical.

B. Hand-held electrical tools, called moistur e meters, should be part of the toolbox of every flooring contractor for measuring moisture in subfloors and floors. Moisture meters have many purposes. They can be used to determine if floor boards are dry enough for an installation to proceed, they can check subfloors and concrete for high moisture levels, they can determine when a second coat of finish can be applied and they can assess water damage.

There are two main types of meters for testing wood: probe and pinless.

1. The probe type measures electrical resistance across opposed sets of pins, which are pushed into the wood. All probes should be inserted parallel with the grain or as instructed by the meter manufacturer. An advantage of probe type meters is that those with insulated pins are able to measure moisture content at varying depths; for example, you can determine whether the moisture content near the bottom of the board is higher than near the top.

2. The pinless, dielectric type employs signal penetration at one inch or more for both hardwood and softwood. The meter can be moved across the surface to identify pockets of moisture. It is relatively unaffected by temperature. Rough surfaces have very little effect on the reading. Measurements can also be taken through coatings, varnish or paint without damage to the surface. Newer pinless meters can be adjusted to depth desired. Older models may read deeper into flooring systems and not give an accurate reading of wood flooring only.

3. Follow the meter manufacturer’s recommendations to get an ac curate reading from the wood floor. One effective testing method is to remove a sample board and get a reading with air space beneath it.

4. It is important that the meter you chose offers the following:

a. A wide moisture content range from at least 6 percent to 30 percent.

b. The necessary adjustment tables, conversion charts or settings for various species. Test for moisture at several locations in the room – a minimum of 20 per 1,000 square feet – and average the results. Document all results. A high reading in one area indicates a problem that must be corrected. Pay special attention to exterior and plumbing walls.


Part II

Moisture Testing for Concrete Slabs

Note: All tests give a result – at the time the test is done – and in general give you the ability to start or not start a job. These tests do not give a permanent condition of your substrate, but merely a “at the time the test was performed” indication.

Testing Requirements
Before moisture testing begins, the concrete slab must be a minimum of 30 days old.

Qualitative Moisture Tests – Electrical Impedance Test and Electrical Resistance Test (Moisture Meter) Follow meter manufacturer’s instructions.

1. Use moisture meters designed specifically for concrete moisture testing.

2. Test within the body of the slab (electrical resistance), as well as at the surface (electrical impedance).

3. These testing methods are not recognized by any standard and should not be used for the purpose of accepting or rejecting a floor. These electronic tests are useful survey tools to broadly evaluate the relative moisture conditions of a slab and to select locations for quantitative moisture tests.

4. If the moisture meters indicate the presence of excessive moisture, as per wood flooring or meter manufacturer’s recommenda tions, further testing is required using relative-humidity testing (ASTM F2170), calcium chloride testing (ASTM F1869) or calcium carbide (CM) testing (ASTM D4944 and MilSpec CRD-C154-77).

Quantitative Moisture Tests

1. ASTM F1869 – Standard Test Method for Measuring Moisture Vapor Emission Rate of Concrete Subfloor using Anhydrous Calcium Chloride.

a. This test method covers the quantitative determination of the rate of moisture vapor emitted from below-grade, on-grade, and above-grade (suspended) bare concrete floors.

2. ASTM F2170 – Standard Test Method for Determining Relative Humidity in Concrete Floor Slabs using in Situ Probes.

a. This test method covers the quantitative determination of percent relative humidity in concrete slabs for field or laboratory tests.

3. ASTM F2659 – Standard Guide for Preliminary Evaluation of Comparative Moisture Condition of Concrete, Gypsum Cement and Other Floor Slabs and Screeds Using a Non-Destructive Electronic Moisture Meter.

a. This guide focuses on obtaining the comparative moisture condition within the upper 1″ (25.4 mm) stratum in concrete, gypsum, anhydrite floor slabs and screeds for field tests. Due to the wide variation of material mixtures and additives used in floor slabs and screeds, this methodology may not be appropriate for all applications. See 1.2 through 1.8 and Section 11 of ASTM F2659. Where appropriate, or when specified, use further testing as outlined in Test Methods F1869, F2170 or F2420 before installing a resilient floor covering.

4. ASTM F2420 – Standard Test Method for Determining Relative Humidity on the Surface of Concrete Floor Slabs Using Relative Humidity Probe Measurement and Insulated Hood.

a. This test method covers the quantitative determination of percent relative humidity above the surface of concrete floor slabs for field or laboratory tests.

5. Relative Humidity Testing – ASTM F2170 (Standard Test Method for Determining Relative Humidity in Concrete Floor Slabs Using In Situ Probes).

a. Select test locations to provide information about moisture distribution across the entire concrete floor slab. For slabs on grade and below grade, include a test location within three feet of each exterior wall.

b. Perform three tests for the first 1,000 square feet and one test for every additional 1,000 square feet thereafter.

c. At least 48 hours before test is placed, concrete floor slabs should be at the same temperature and humidity that is expected during service conditions.

d. Use a rotary hammer-drill to drill holes in the concrete slab; 40% depth of slab is required for the holes when concrete is drying from one side and 20% when drying from both sides. Follow manufacturer’s instructions provided with test kits.

e. Allow 72 hours to achieve moisture equilibrium within the hole before making relative humidity measurements. Follow manufacturer’s instructions provided with test kits.

f. ASTM F710 provides installation guidelines for acceptance of hardwood flooring using relative humidity testing. Typical limits for wood and wood-based products are 75% relative humidity. When getting readings over 75%, you must use a proper vapor retarder, based on the flooring manufacturer’s recommendations, or wait for further concrete curing.

6. Calcium Chloride Test – ASTM F1869 (Test Method for Measuring Moisture Vapor Emission Rate of Concrete Subfloor Using Anhydrous Calcium Chloride).

a. Select test locations to provide information about moisture distribution across the entire concrete floor slab.

b. Perform three tests per 1,000 square feet of surface area. Add one additional test for each 1,000 square feet thereafter. At least 48 hours before test is placed, concrete floor slabs should be at the same temperature and humidity expected during service conditions.

d. The actual test area shall be clean and free of all foreign substances. Use approved OSHA work practices for removal of all existing flooring materials and debris.

e. Blast or grind a minimum area of 20 inches by 20 inches and let stand for a minimum period of 24 hours prior to setting test.

f. Follow manufacturer’s instructions for properly placing tests onto concrete.

g. Tests are to be covered and left in place for 60 to 72 hours. Follow manufacturer’s instructions for labeling and recording time and date of test.

h. Send the test to a certified laboratory for results and documentation, or perform the measurements as per ASTM F1869.

i. Always follow the flooring manufacturer’s guidelines and specifications to determine when the concrete slab is ready for installation.

j. ASTM F710 provides installation guidelines for acceptance of hardwood flooring using alciumchloride testing. Typical limit for direct glue-down wood flooring is 3lbs/1000sf/24hr. When getting readings over 3lbs and up to 7lbs, you must use a vapor retarder. A reading over 7lbs may not be acceptable for wood flooring installation. Follow the wood flooring manufacturer’s recommendations. In the case of a glue-down installation, the adhesive manufacturer may also have recommendations. Note: For information on the tests listed above, contact your distributor or call NWFA at 800.422.4556 (USA or Canada) or 636.519.9663 for the source nearest you.

7. Calcium Carbide (CM) Test – ASTM (modified) D4944, MilSpec CRD-C154-77.

a. The calcium carbide test, also known as the CM test or calcium carbide bomb, is more widely used in Europe than in the United States. It is a gas-pressure test in which moisture in the concrete reacts with calcium carbide crystals to create acetylene gas, and the gas pressure produced is measured to provide a moisture content reading, expressed as a percentage of moisture. Follow the directions provided by the test-kit manufacturer. A reading of more than 2.5% requires use of a vapor retarder. A reading of more than 4% may not be acceptable for wood flooring installation. Follow the wood flooring manufacturer’s recommendations. In the case of a glue-down installation, the adhesive manufacturer may also have recommendations.


Part III

Acceptable Vapor Retarders Over Wood Subfloors

A. Always follow local codes and manufacturer’s instructions for acceptable vapor retarders. Note: The 2012 IBC defines three classes of vapor retarders:

1. Class I 0.1 perm or less.

2. Class II 0.1 perm less than or equal to 1.0 perm.

3. Class III 1.0 perm less than or equal to 10 perm. When tested in accordance with ASTM E96 Method A.

B. An acceptable vapor retarder is a vapor resistant material, membrane or covering with a vapor permeance (perm rating) of greater than or equal to .7 and less than or equal to 10 when tested in accordance with ASTM E96 Method A. Installation of a vapor retarder reduces the potential for moisture or vapor related problems, but does not guarantee elimination of moisture or vapor related problems. Install a vapor retarder over wood panel or board subfloors prior to installing nail down solid strip or plank flooring. Overlap seams a minimum of 4 inches or more as required by manufacturer or specifier and local building codes.

Some examples of acceptable vapor retarders over wood subfloors include:

1. An asphalt laminated paper meeting UU-B-790a, Grade B, Type I, Style 1a.

2. Asphalt-saturated kraft paper or #15 or #30 felt paper meeting ASTM Standard D4869 or UU-B-790.

Note:
1. A vapor retarder has some extra benefits in that it eliminates wood-on-wood contact, wood strips slide more easily when positioned, it minimizes the impact of seasonal humidity change and it may reduce dust and noise levels.

2. However, by today’s standards, asphalt saturated kraft or felt paper may not be an effective vapor retarder, with a Class III perm rating of 1.0 perm <10, in all applications. Consult local codes.

3. Over a wood subfloor, do not use an impermeable vapor retarder material with a perm rating of .7 or less, such as 6 mil polyethylene film or other polymer materials, as it may trap moisture on or in the wood subfloor. Such impermeable material may be used if recommended by the wood flooring manufacturer as such materials have been measured for vapor transmission due to fastener penetration or include special backing to dissipate vapor horizontally.


Part IV

Acceptable Vapor Retarders Over Concrete

A. Always follow local codes and manufacturer’s instructions for acceptable vapor retarders.

B. Test concrete for moisture. For concrete slabs with a calcium chloride reading of greater than 3lbs, a relative humidity reading of greater than 75%, or a calcium carbide (CM) rating of greater than 2.5%, install an impermeable vapor retarder with a perm rating of less than .15 perm. Adding a vapor retarder is not required on installations over slabs with a calcium chloride reading of 3lbs or less, a humidity reading of 75% or less, or a calcium carbide (CM) rating of 2.5% or less. However, in on-grade and below-grade applications, adding a vapor retarder is always recommended.

C. The 2012 IBC defines three classes of vapor retarders:

1. Class I 0.1 perm or less.

2. Class II 0.1 perm less than or equal to 1.0 perm.

3. Class III 1.0 perm less than or equal to 10 perm. When tested in accordance with ASTM E96 Method A.

D. The NWFA recommends an “impermeable” vapor retarder with a perm rating of less than or equal to .15, thereby limiting the passage of moisture to near zero.

E. Some acceptable vapor retarders over concrete include:

1. A minimum 6 mil construction grade polyethylene film or other impermeable material with a perm of .15 or less is recommended. A premium polymer material meeting ASTM E1745 for concrete with higher tensile, tear and puncture resistance is highly desirable.

2. Double felt: Two layers of #15 asphalt saturated felt paper that meets ASTM Standard D4869, with the first layer adhered to the slap in a skim coat of appropriate asphalt mastic type adhesive recommended by manufacturer, and a second layer felt adhered to the first layer with same appropriate adhesive.

3. A chemical retarder or urethane membrane, as recommended by the adhesive or wood flooring manufacturer. These are usually in the form of a liquid-applied or trowel-applied membrane dispensed from a bucket following manufacturer recommendations.

4. Installation membrane: a permanently elastic, cross linked, closed cell polyethylene membrane. Follow membrane manufacturer instructions.

5. A loose laid or mechanically fastened plastic, waterproof, dimple type membrane, providing a thermal air gap separating finished floor from concrete. Follow membrane and floor manufacturer installation instructions.

6. An elastomeric, fully adhered or mechanically fastened membrane with seams sealed. Follow membrane manufacturer installation recommendations.


Part V

Dimensional Change of Coefficients

A. See Solid Strip and Plank Flooring Installation, for dimensional change of coefficients.

Installation – Wood Subfloor Guidelines

Proper wide plank flooring installation begins with these wood subfloor specification, flatness & moisture guidelines.

Note: Always follow the wood flooring manufacturer’s recommendation for a proper subfloor.


Part I

Wood Subfloor Specifications

A. Subfloor panels should conform to U.S. Voluntary Product Standard PS1-07, Construction and Industrial Plywood and/or US Voluntary PS 2-04 and/or Canadian performance standard CAN/CSA 0325.0-92 Construction Sheathing. Other CSA standards also apply.

B. Solid-board subflooring should be ¾” x 5½” (1″ x 6″ nominal), Group 1 dense softwoods, No. 2 Common, kilndried to less than 15 percent moisture content.

C. Both CD Exposure 1 plywood and OSB Exposure 1 subfloor panels are appropriate subflooring materials, but the proper thickness of the material will be determined by the factors noted below in Part IV, Panel Products Subflooring, E, Acceptable Panel Subfloors.


Part II

Subfloor Moisture

Note: The National Association of Home Builders’ Green Home Building Guidelines contain the following directive under Section 5.3.8: “NA HB Model Green Home Building Guidelines, Section 5.3.8: Check moisture content of wood flooring before enclosing on both sides. Ensure moisture content of subfloor/substrate meets the appropriate industry standard for the flooring material to be installed.”

A. For solid strip flooring (less than 3″ wide), there should be no more than 4 percent moisture content difference between properly acclimated wood flooring and subflooring materials.

B. For wide-width solid flooring (3″ or wider), there should be no more than 2 percent difference in moisture content between properly acclimated wood flooring and subflooring materials.


Part III

Subfloor Flatness and Integrity

A. Wood subfloors must be flat, clean, dry, structurally sound, free of squeaks and free of protruding fasteners.

1. For installations using mechanical fasteners of 1½” and longer, the subfloor should be flat to within ¼” in 10 feet or 3/16″ in 6 feet radius.

2. For glue-down installations and installations using mechanical fasteners of less than 1½”, the subfloor should be flat to within 3/16″ in 10 feet or 1/8″ in 6 feet radius.

B. If peaks or valleys in the subfloor exceed the tolerances specified above, sand down the high spots and fill the low spots with a leveling compound or other material approved for use under wood flooring. However, it is the builder’s or general contractor’s responsibility to provide the wood-flooring contractor with a subfloor that is within the tolerances listed above.

When possible, check the back of the subfloor panel for American Plywood Association (APA) rating.

APA Plywood Rating

C. Inspect the subfloor carefully. If there is movement or squeaks in the subfloor, refasten the subfloor to the joists in problem areas.

D. Protruding fasteners are easily remedied by driving those fasteners deeper into the subfloor.


Part IV

Panel Products Subflooring

A. For panel products subflooring, check for loose panels and renail or screw down loose panels securely.

B. Ensure that there is proper expansion space (1/8″) between the panels. If the subfloor panels are not tongueand- grooved and if there is not sufficient expansion space, use a circular saw to create the specified space. Do not saw through joints on T&G subfloors.

C. Also check for delaminated or damaged areas and repair those areas as needed.

D. Make sure the subfloor is free of debris before beginning installation.

E. Acceptable Panel Subfloors: Truss/joist spacing will determine the minimum acceptable thickness of the panel subflooring.

1. On truss/joist spacing of 16″ (406mm) o/c or less, the industry standard for single -panel subflooring is minimum 5/8″ (19/32″, 15.1mm) CD Exposure 1 Plywood subfloor panels (CD Exposure 1) or 23/32 OSB Exposure 1 subfloor panels, 4′ x 8′ sheets.

2. On truss/joist spacing of more than 16″, up to 19.2″ (488mm) o/c, the standard is minimum ¾” (23/32″, 18.3mm) T&G CD Exposure 1 Plywood subfloor panels, (Exposure 1), 4′ x 8′ sheets, glued and mechanically fastened, or minimum ¾” (23/32″, 18.3mm) OSB Exposure 1 subfloor panels, 4′ x 8′ sheets, glued and mechanically fastened. When possible, check the back of the subfloor panel for American Plywood Association (APA) rating.

3. Truss/joist systems spaced over more than 19.2″ (488mm) o/c up to a maximum of 24″ (610mm) require minimum 7/8″ T&G CD E xposure 1 Plywood subfloor panels, (Exposure 1), 4′ x 8′ sheets, glued and mechanically fastened, or nominal 1″ OSB Exposure 1 subfloor panels, 4′ x 8′ sheets, glued and mechanically fastened – or two layers of subflooring. Or brace between truss/joists in accordance with the truss/joist manufacturer’s recommendations and with local building codes. Some truss/joist systems cannot be cross-braced and still maintain stability.

a. For double-layer subfloors, the first layer should consist of nominal ¾” (23/32″, 18.3mm) CD Exposure

1 Plywood subfloor panels (CDX), 4′ x 8′ sheets or nominal ¾” (23/32″ , 18.3mm) OSB Exposure 1 subfloor panels, 4′ x 8′ sheets. The second layer should consist of nominal ½” (15/32″, 11.9mm) CD Exposure 1 plywood subfloor panels, (Exposure 1) 4′ x 8′ sheets. The ½” plywood should be offset by ½” panels in each direction to the existing subflooring. The panels may also be laid on a diagonal or perpendicular, with 1/8″ spacing between sheets. Nail on a 12″ minimum grid pattern, using ring shanked nails or staples.

F. Fastening and Spacing Specifications

1. Follow the panel manufacturer’s recommendations for spacing and fastening.

2. Typical panel spacing and fastening requirements for truss/joist systems call for approximately 1/8″ (3.2mm) expansion space around the perimeter of each panel, with panels fastened every 12″ (305 mm) along intermediate supports.

3. Edge swell should also be flattened. This can usually be accomplished by using an edger sander.


Part V

Solid Board Subflooring

A. Solid board subflooring should be: ¾” x 5½” (1″ x 6″ ), Group 1 dense softwoods (SYP, Doug Fir, Larch, etc.), No.

2 Common, kiln-dried to less than 15% MC. Refer to Chapter 2, Acclimation and Conditioning of Wood Flooring, for proper subfloor moisture content at time of installation.

B. Solid-board subflooring should consist of boards no wider than 6 inches, installed on a 45-degree angle, with all board ends full bearing on the joists and fastened with minimum 8d rosin-coated or ring-shanked nails, or equivalent.

C. Some types of wood flooring should not be installed directly over solid-board subflooring.

1. Thin-classification solid strip flooring must have a 3/8″or better plywood underlayment installed over solid board subflooring.

2. Parquet flooring cannot be installed directly to solid-board subfloors. A parquet installation over solidboard subflooring requires 3/8″ or better underlayment panels, nailed on 6″ minimum grid pattern using ring-shanked nails or staples.

D. Some engineered flooring cannot be installed directly to solid-board subfloors. (See wood flooring manufacturer’s recommendations.) – Olde Wood’s can.

Installation – Concrete Subfloor Guidelines

Important guidelines for subflooring to be placed over concrete surfaces.

Note: Always follow the wood flooring and adhesive manufacturer’s recommendation for a proper subfloor.


Part I

Concrete Subfloor Specifications

A. Subfloor must be flat.

1. Make sure the concrete slab is flat to the wood flooring manufacturer’s specification. Typically, manufacturers will specify a flatness tolerance of 1/8″in a 6 -foot radius and or 3/16″ in a 10 -foot radius.

2. If the slab is out of specification, consider grinding, floating or both. Many high spots can be removed by grinding, depressions can be filled with approved patching compounds, and slabs also can be flattened using a self-leveling concrete product.

3. When sanding or grinding concrete, care must be taken to minimize the amount of silica dust produced. OSHA recommends using dust-collection devices, or applying water to the concrete before sanding. Approved respirators may also be used to minimize the amount of silica dust inhaled.

B. Subfloor must be dry.

1. See Moisture Guideline Testing and Vapor Retarders.

2. Concrete moisture meters and other tests can be useful in identifying moisture problem areas. However, NWFA guidelines specify using relative-humidity testing (ASTM F2170), calcium chloride testing (ASTM F1869) or calcium carbide (CM) testing (ASTM D4944 and MilSpec CRD-C154-77) to identify the moisture content of the slab. See Chapter 3, Moisture Guideline and Vapor Retarders.

3. If a slab tests too high in vapor emission to glue a floor down, consider using a vapor retarder type product, installing a vapor retarder and a plywood subfloor or using an alternative installation method.

4. Concrete slabs with a calcium chloride reading of more than 3 require use of a vapor retarder with a perm rating of 1 or less. It is strongly recommended to use an impermeable vapor retarder with a perm rating of .13 or less, such as 6 mil polyethylene film.

C. Slab must be:

1. Minimum 3000 psi.

2. Free from non-compatible sealers, waxes, oil, paint, drywall compound, etc.

a. Check for the presence of sealers by applying drops of water to the slab. If the water beads up, there may be sealers or oils.

D. Do not attempt to glue a wood floor over a chalky or soft concrete slab.

E. Burnished or slick slabs may require screening or sanding with a 30-grit abrasive.

F. Specifications for lightweight concrete:

1. Make sure the concrete is well bonded to the subfloor. Check for hollow spots, cracks and loose areas.

2. As with on-grade concrete subfloors, make sure the concrete is clean, flat to specification and dry.

3. Over lightweight concrete (less than 3000 psi), if the flooring adhesive used has a higher shear strength than the concrete, use the floated subfloor installation method. (See Installing a Subfloor OverConcrete.) If the psi of the concrete is unknown, use the floated subfloor installation method or contact the adhesive manufacturer.

4. Rule of thumb: Draw a nail across the top; if it leaves an indentation, it is probably lightweight concrete.

Installation – Subfloor Over Concrete

Wondering how to install a subfloor over concrete? These important guidelines will get you started.

Note: Always follow the manufacturer’s recommendation for a proper subfloor.


Part I

Direct Gluing a Subfloor Over Concrete

A. Always follow the adhesive manufacturer’s recommendation for proper application, proper adhesive and correct trowel notch and spread rate.

B. If necessary, add vapor retarder recommended by the adhesive manufacturer before applying adhesive.


Part II

Floated Subfloor

A. In on-grade and below-grade applications, always add vapor retarder before applying underlayment.

B. In above-grade applications, follow the flooring manufacturer’s recommendations.

C. A vapor retarder is recommended anytime solid ¾” wood flooring is installed over concrete. A vapor retarder is required for installation over concrete with a calcium chloride reading greater than 3 pounds, a relative humidity reading of greater than 75%, or a calcium carbide (CM) reading of greater than 2.5%.

D. Floated Subfloor System

1. Materials

a. 2 layers minimum 3/8″ (10mm) minimum CD Exposure 1 Plywood subfloor panels (CDX) 4′ x 8′ sheets.

2. Installation method

a. Place the first plywood layer with edges parallel to wall, without fastening. Leave ¾” space between wall and plywood.

b. Plywood panels should be placed with 1/8″ gaps between sheets.

c. Lay the second layer perpendicular or at 45 degree angle to the first.

d. Plywood panels should be placed with 1/8″ gaps between sheets and a ¾” minimum expansion space at all vertical obstructions and wall lines.

e. Staple/screw and glue (with urethane or construction adhesive) the second layer to first layer on 12″ interior grid pattern (6″ on the perimeter). Be careful not to penetrate the vapor retarder.

E. Alternate Subfloor System

1. Materials

a. Use minimum ¾” (23/32″, 18.3mm) CD Exposure 1 Plywood sheathing, 4′ x 8′ sheets.

2. Installation method

a. Cut sheets to 16″ x 8′ or smaller panels, scored on back 3/8″ deep a minimum of every 12″ across width.

b. 16″ planks oriented perpendicular or diagonally to direction of flooring.

c. Panels staggered every 2′, and spaced 1/8″ between ends, with ¾” minimum expansion space at all vertical obstructions.


Part III

Glue-Down Subfloor

A. Always follow the adhesive manufacturer’s recommendation for proper subfloor, spread rate and trowel notch.

B. If necessary, add vapor retarder before applying underlayment. A vapor retarder is recommended anytime solid ¾” wood flooring is installed over concrete.

C. Glue-Down Subfloor System:

1. Materials

a. Use minimum ¾” (23/32, 18.3mm) CD Exposure 1 Plywood subfloor panels, (Exposure 1), 4′ x 8′ sheets.

2. Installation method

a. Cut the plywood panels to 2′ x 8′ or 4′ x 4′ sections.

b. Score the back of the panels ½ the thickness on a 12″ x 12″ grid.

c. Apply an adhesive approved for the installation of plywood, per the plywood manufacturer’s recommendations.

d. Lay sections in a staggered joint pattern in the adhesive, with 1/8″ spacing between sheets, and ¾” minimum expansion space at walls and all vertical obstructions.


Part IV

Nail-Down Subfloor

A. Always follow the manufacturer’s recommendation for proper subfloor.

B. In on-grade and below-grade applications, always add vapor retarder before applying underlayment. In abovegrade applications, follow the flooring manufacturer’s recommendations.

C. A vapor retarder is recommended anytime solid ¾” wood flooring is installed over concrete.

D. Nail-Down Subfloor System Over Concrete

1. Materials

a. Minimum: Use minimum ¾” (23/32, 18.3mm) CD Exposure 1 Plywood subfloor panels (CDX), 4′ x 8′ sheets.

2. Installation method – Note: Fasteners may be powder-driven pins, pneumatic driven nails, screws, deformed pins, or other fasteners suitable for concrete application. Check with fastener manufacturer for specification such as length, drill size, and/or shot load where applicable.

a. Stagger panel joints allowing approximately 1/8″ expansion space around all panels to prevent edge peaking due to compression caused by panel swell.

b. Allow ¾” minimum expansion space at all vertical obstructions.

c. Panels should be mechanically fastened. For powder load or pneumatic pressure information, contact your local supplier.

d. Nailing requirements, minimum 32 shots per 4′ x 8′ panel.

e. Areas with higher humidity may require additional fasteners.


Part V

Screed System

A. Solid ¾”, 25/32″ and 33/32″ tongue -and-groove strip flooring may be installed directly to screeds.

B. Engineered wood flooring less than ¾” (23/32″) thick, thin -classification strip flooring (including ½”) and solid plank flooring (3″ or wider) cannot be installed directly to screeds.

C. For engineered flooring less than ¾” thick, thin -classification strip, and for solid plank (3″ and wider), the screed system must be overlaid with proper subflooring. The screed system must be overlaid with nominal ¾” (23/32″, 18.3mm) Exposure 1, or nominal 5/8″ (19/32″, 15.1mm), Exposure 1, CDX plywood subfloor panels or nominal ¾” (23/32″, 18.3mm) OSB underlayment properly spaced and oriented perpendicular to screed direction. All joints must be staggered.

D. Installation method. See Appendix I, Installation Over Screeds.

Guides on how to plan, layout and install parquet flooring.


Part I

Acceptable Jobsite Conditions and Jobsite Checklist

A. See Jobsite Conditions.


Part II

Acclimation Guidelines

A. See Acclimation and Conditioning of Wood Flooring.


Part III

Appropriate Grade Levels

A. Solid parquet wood floors can be installed successfully above grade level or on grade, but are not recommended for installation below grade.

B. The entire flooring level is considered to be below grade where soil is present along any perimeter wall and is more than 3″ above the installed wood flooring level. Ground should be sloped away from the house for proper drainage. (Follow local building codes.)


Part IV

Subfloors – Wood Joist Systems

A. See Wood Subfloor Guidelines.

B. Parquet cannot be installed directly to solid board subfloors. For parquet installations, board subfloors must have additional underlayment.


Part V

Subfloors – Concrete Slab

A. See Concrete Subfloor Guidelines


Part VI

Parquet Installation Methods

A. Follow manufacturer’s recommendations.

1. The styles and types of block and parquet flooring, as well as the recommended procedures for application, vary somewhat among manufacturers. Detailed installation instructions are usually provided with the flooring or are available from the manufacturer or distributor.

B. Test wood subflooring for moisture according to moisture testing procedures. (See Moisture Guideline and Vapor Retarders.)

C. Test concrete for moisture according to moisture testing procedures in Moisture Guideline and Vapor Retarders. Moisture indicators should be within the adhesive and flooring manufacturers’ specifications.

D. A minimum expansion space of ½” must be left around the perimeter and all vertical obstructions.

E. Some ¾” parquet is appropriate for nail-down installation, as long as the pattern continues to have an exposed side tongue in which to nail.

F. Lay blocks and/or individual pieces of parquet in adhesive.

G. Use the wood manufacturer’s approved adhesive. Follow the spread rate, trowel size and installation procedure as recommended by the adhesive manufacturer.

Figure 1-2


Part VII

Parquet Layouts

A. Square Layout from the Center of the Room (See Figure 7-1) Note: For instructions on using the trammel point method to square a room and find the center point, see Appendix G, Trammel Point Method.

1. Start by snapping a chalk line through the center of the room (line Y). The next line (X) must be exactly 90 degrees to line Y to form a perfect square corner. To ensure this angle, do the following:

2. From the center point (A) of line Y, measure 4 feet along line Y and mark that point (B).

3. From the same center point, measure 3 feet in the general direction of where line X will be and scribe an arc.

4. Return to the original 4-foot mark on line Y and measure 5 feet, scribing an arc that crosses (point C) the 3-foot arc you made in the previous step.

5. Verify all measurements before proceeding.

6. If correct, snap a chalk line through the conjunction of the two arcs at point C and the center point of line

Y. This will be line X, at an exact 90-degree angle to line Y.

B. Square Layout from the Wall (See Figure 7-2) Square edge block or basket weave pattern can be laid wall to wall without centering the tiles on the room. The results will not be balanced but the tiles have no edge treatment to delineate the difference in tile sizes when unbalanced. More intricate patterns generally require the flooring to be centered.

1. Wall Line Layout

a. If the room dimensions allow, in at least two places from the corner, measure out and establish a chalk line parallel to and 24-1/2″ (62cm) away from the starting wall opposite the entrance doorway. The 1/2″ (12.7 mm) is for expansion space.

b. Snap a second chalk line 90 degrees to the first chalk line using the method shown in Figure 7-2, 24-1/2″ (62cm) away from the right angle wall. The ½” is for expansion space.

c. Make any necessary adjustments to allow for walls out of square before proceeding.

C. Installation Using Wall Layout (See Figure 7-3)

1. Spread the Adhesive

a. After both chalk lines (at 90 degrees to each other and 24-1/2″ (62cm) from the wall) have beensnapped, start spreading the adhesive in the 24-1/2″ (62cm) wide area next to the starting wall.

b. Continue spreading the adhesive along the entire length of the starting wall. Be careful not to spread adhesive beyond the 24-1/2″ (62cm) chalk line.

2. Immediately lay the floor tiles on the newly spread adhesive.

3. Do not lay the floor tiles on dry adhesive. If the adhesive becomes too dry, scrape up the old adhesive and spread more.

4. Important: Stand or kneel on the subfloor during the installation to avoid shifting the tiles.

5. Proper placement of the first floor tile is the key to the entire installation. Carefully place a 12″ x 12″ (30 x 30 cm) parquet tile at the intersection of the two chalk lines. (See Figure 7-3.) Do not use the edge of the tongue for aligning the tile on the chalk lines.

When the starting area has been completed, including cutting to the wall, proceed to the second laying area, then to laying areas 3, 4, 5, etc., repeating the installation procedure of the starting area.

6. Lay the second floor tile ahead of the first tile to fit 1/2″ (12.7 mm) from the starting wall. Gently lock in the tongue and groove between the first and second floor tiles.

7. Recheck to be sure both floor tiles are properly lined up with the chalk line. This is to ensure a square starting area.

8. Continue laying the balance of the 12′ x 12′ (30.48cm) floor tiles along the starting wall area. Put each floor tile in place and gently push the floor tiles together to interlock the tongue and groove. Align each floor tile squarely.

9. Do not push the floor tiles too strenuously as this could cause the first and second floor tiles to move. Simply realign them and proceed with the installation. Avoid hammering or forcing the floor tiles together as this may destroy the squareness of the floor tile.

10. After laying the floor tiles across the first 24-1/2″(30.48 cm) starting area, trim the last floor tiles as needed to obtain the proper 1/2″ (12.7 mm) expansion space next to the walls. Use a small band or saber saw for final trimming. Firmly secure each floor tile when cutting with a saber saw.

11. Complete the installation.

a. When the starting area has been completed, including cutting to the wall, proceed to the second laying area. (See Figures 7-3.)

b. Cut the last floor tiles to allow a 1/2″ (12.7 mm) expansion space from the end wall.

c. Proceed by laying areas 3, 4, 5, etc., repeating the installation procedure of the starting area. Trim out each laying area before proceeding to the next area.

d. Maintain the 1/2″ (12.7 mm) expansion space around the perimeter of the room and around all fixed objects.

e. Allow a minimum of 24 hours drying time before moving furniture or walking on the newly laid parquet floor.

D. Diagonal Layout (See Figure 7-4)

1. Establish a 45-degree working line.

2. From the center point, measure 4 feet down in each direction on lines X and Y, which you have already determined by the method described previously.

3. From each of these points, measure 4 feet and scribe an arc. The conjunction of these arcs creates points D and E.

4. Snap a chalk line between points D and E, and the center point. This line represents a 45-degree angle.

E. Herringbone Layout

1. Use reference lines throughout the area that is being installed.

2. The multiple of the width should equal the exact length of the piece. If the width of the product varies, this will cause separations at the end of the herringbone pieces.

3. Herringbone parquet can be laid out parallel or at a 45-degree angle to the room. Regardless of direction, Herringbone parquet will require a centerline and two working lines (See Figure 7-5).

4. Begin by laying out a few alternating slats.

5. Snap lines A & B through the corners of the alternating slats (See Figure 7-5).

6. Measure the distance from Line A to Line B. Line C should be 1/2 that distance and run parallel to Lines A & B. The centerline of the room and the center of the pattern is represented by Line C.

F. Herringbone Installation

1. To begin installation on working Line B (See Figure 7-6), cut a square piece of plywood the size of the herringbone pattern. For example, if the herringbone pattern is 3″ x 12″, cut a 12″ x 12″ square of plywood.

2. Fasten the piece of plywood at your starting point on Line B, with one corner of the square pointing in the direction of the pattern.

How do I install engineered hardwood flooring? Well, use these informative guidelines to steer you in the right direction.


Part I

Acceptable Jobsite Conditions and Jobsite Checklist

A. See Jobsite Conditions.


Part II

Acclimation Guidelines

A. See Acclimation and Conditioning of WoodFlooring.


Part III

Appropriate Grade Levels

A. Engineered wood floors can be installed successfully on, above or below grade level. Engineered wood floors can be installed directly to a concrete or wood subfloor.

B. The entire flooring level is considered to be below grade where soil is present along any perimeter wall and is more than 3″ above the installed wood flooring level. Ground should be sloped away from the house for proper drainage. (Check local building codes. Local building codes prevail. Follow local building codes.)


Part IV

Subfloors – Wood Joist Systems

A. See Wood Subfloor Guidelines.


Part V

Subfloors – Concrete Slab

A. See Concrete Subfloor Guidelines, and Installing a Subfloor Over Concrete.


Part VI

Engineered Flooring Installation Methods

A. Engineered wood flooring can be installed directly to screeds, provided the engineered flooring is a minimum of ¾” thick. For engineered flooring less than ¾” thick, the screed system must be overlaid with proper subflooring. See Appendix I, Installation Over Screeds.

B. Note on random-width plank.
Random-width plank is laid out with alternating courses varying by widths. Start with the widest board, then the next width, etc., and repeat the pattern.

C. Choose a starting wall.
Choose a starting wall according to the most aesthetically or architecturally important elements in the room, taking into consideration fireplaces, doors, cabinets and transitions, as well as the squareness of the room. The starting wall will often be the longest unbroken wall in the room.

D. Glue-down engineered strip and plank.

  1. There are several different ways to start the installation of glue-down engineered wood flooring. The following has proven successful. However, where instructions differ from manufacturer recommendations, manufacturer recommendations prevail.
  2. Test the substrate for moisture according to appropriate moisture testing procedures inMoisture Guideline and Vapor Retarders. Excessive/elevated moisture should not be present. The subfloor should be within acceptable moisture content as per adhesive and wood manufacturer’s recommendation before installing.
  3. Expansion space should be left around the perimeter in accordance with the manufacturer’s recommendation.
  4. Snap a working line parallel to the starting wall, the width of the board, plus the tongue and recommended expansion space.
  5. Install a starter board along the edge of the working line and begin installation. Alternatively, lay one row of plank in the adhesive along the length of the working line.
  6. Follow manufacturer instruction for tongue and groove direction and placement.
  7. Use an adhesive approved by the flooring manufacturer. Follow the installation procedure recommended by the adhesive manufacturer, which includes subfloor moisture content, spread rate, trowel size, open time, working time and flash time as necessary. Spread the adhesive as instructed up to and along the working line.
  8. Distribute lengths, avoiding “H” patterns and other discernible patterns in adjacent runs. Stagger end joints of boards row to row a minimum of 6″ for strip flooring, 8″ -10″ for 3″ to 5″ plank, and 10″ for plank wider than 5″. (See Figures 8 -1 and 8-2.)
  9. If recommended by the manufacturer, use tape or tensioners to maintain a tight floor.
  10. If recommended by the adhesive manufacturer, roll the floor with the proper roller.

E. Mechanically fastened strip and plank.

  1. If necessary, add a vapor retarder.
  2. Snap a working line parallel to the starting wall, allowing expansion space as specified by the manufacturer.
  3. Lay one row of plank along the entire length of the working line.
  4. Top-nail and blind-nail the first row (hand-nail if necessary), using appropriate fasteners. Denser species may require pre-drilling. Each succeeding row should be blind-nailed wherever possible.
    • Typical: Narrow crowned (under 3/8″) 1″ -1½” staples or 1″ -1¼” hardwood flooring cleats designed for engineered flooring, spaced as recommended by the manufacturer.
    • Typical: Every 3″ -4″ with staples, every 4″ -6″ with cleats, and within 1″ -2″ of end joints. Use appropriate size fastener for top nailing first row, last row and any area where blind nailer will not fit.
  5. Add each additional row of flooring. Distribute lengths, avoiding “H” patterns and other discernible patterns in adjacent runs. Stagger end joints at least three times the width of the boards, as product allows.
  6. During installation of flooring pieces, push or gently tap boards flush to the previous row. Tap against the tongue; tapping the groove may damage the edge. To prevent damage to the finish, avoid tapping the face of the board with a rubber mallet.

F. Floating engineered flooring.

  1. Subfloor flatness is critical to the success of a floating floor installation. (See Wood SubfloorGuidelines, and Concrete Subfloor Guidelines.)
  2. Test the substrate for moisture according to appropriate moisture testing procedures inMoisture Guideline and Vapor Retarders. Excessive/elevated moisture should not be present. The subfloor should be within acceptable moisture content as per manufacturer recommendation before installing.
  3. If necessary, add vapor retarder.
  4. Expansion space should be left around the perimeter or in accordance with manufacturer’s recommendation.
  5. Typical: Subfloors are covered with a resilient material, foam underlayment or cork. Follow manufacturer’s instructions for correct materials and thickness.
  6. Typical: Floating engineered flooring is edge-glued or edge-attached with a self-locking mechanism.
    • For edge-glued products, use a glue approved by the flooring manufacturer.
    • Apply glue at the spread rate to the side grooves and/or ends as recommended by the flooring manufacturer.
  7. Starter boards should be aligned with the groove side and end against the starting wall. Tapping block should be used against tongue only.
  8. Stagger end joints per manufacturer’s recommendation.

Installation – Solid Wood Flooring

VWondering how to install solid hardwood flooring? Follow these guidelines on solid strip and plank flooring installation.


Part I

Acceptable Jobsite Conditions and Jobsite Checklist

A. See Jobsite Conditions.


Part II

Acclimation Guidelines

A. See Acclimation and Conditioning of Wood Flooring.


Part III

Appropriate Grade Levels

A. Solid strip and plank wood floors can be installed successfully above grade level or on grade, but are not recommended for installation below grade.

B. The entire flooring level is considered to be below grade where soil is present along any perimeter wall and is more than 3″ above the installed wood flooring level. Ground should be sloped away from the house for proper drainage. (Follow local building codes.)


Part IV

Subfloors – Wood Joist Systems

A. See Wood Subfloor Guidelines.


Part V

Subfloors – Concrete Slab

A. See Concrete Subfloor Guidelines.

B. When installing solid strip and solid plank flooring over concrete, a vapor retarder is always required over the concrete slab and below the subflooring material. A minimum 6 mil construction grade polyethylene film, with perm of .13, or other impermeable material with a perm of .15 or less is recommended.

C. Some manufacturers allow direct glue installation of ¾” solid strip and solid plank flooring. In such cases, follow wood or adhesive manufacturer’s recommendation.


Part VI

Solid Strip & Plank Installation Methods

Floor preparation: Refasten any loose areas of subfloor and clean the subfloor by sweeping, scraping, etc., as necessary. With frame construction, mark location of joists on perimeter walls so that starting runs and finishing runs, which require face nailing, can be nailed into joists. Marking also locates the joists for plank flooring installation. Flooring direction: In general over single layer subfloor, wood should be installed perpendicular to the floor truss.

A. Always follow the manufacturer’s recommended installation procedure.

B. Unfinished and factory-finished solid strip and solid plank flooring should be installed perpendicular to the joists or on a diagonal for any single layer subfloor. (Exception: Over diagonal, solid subfloor boards, install perpendicular to joists or subfloor direction.)

C. When ¾” solid strip and solid plank flooring is laid parallel with the floor joists, follow one of these two steps below:

1. Add a layer of minimum ½” (15/32) CD Exposure 1 (CDX) plywood underlayment to the existing subfloor (as previously recommended).

2. Or brace between truss/joists in accordance with the truss/joist manufacturer’s recommendations and with local building codes. Some truss/joist systems cannot be cross-braced and still maintain stability.

D. Before installing wood flooring, use an approved vapor retarder. Some examples of acceptable vapor retarders over wood subfloors include:

1. An asphalt laminated paper meeting UU-B-790a, Grade B, Type I, Style 1a.

2. Asphalt-saturated kraft paper or #15 or #30 felt that meets ASTM Standard D4869 or UU-B-790, Grade D.

3. Cover the subfloor with a good grade of #2 vapor retarders ASTM 4869, lapped 2″ – 4″ along the edge seams. This retards moisture movement from below. Extend the felt/building paper completely to the walls. It is necessary to fasten the felt to the subfloor.

E. Wall Line Layout

1. Choose a starting wall according to the most aesthetically or architecturally important elements in the room, taking into consideration fireplaces, doors, cabinets and transitions, as well as the squareness of the room. The starting wall will often be the longest unbroken wall in the room.

2. Snap a working line parallel to the starting wall, allowing ¾” expansion space between the starting wall and the edge of the first strip or plank run.

3. As a general rule, a ¾” expansion space must be left around the perimeter and at all vertical obstructions.

4. Random-width plank is laid out with alternating courses varying by widths. Start with the widest board, then the next width, etc., and repeat the pattern.

5. Lay one row of strip or plank along the entire length of the working line.

6. Top-nail and blind-nail the first row (hand-nail if necessary), using appropriate fasteners. Denser species may require pre-drilling. Each succeeding row should be blind-nailed with the nailing machine wherever possible. At the finishing wall and other obstructions, it may be necessary to blind-nail by hand until top nailing is required.

7. Racking rule of thumb: Avoid H patterns. Stagger end joints of boards row to row a minimum of 6″ for strip flooring, 8″-10″ for 3″ to 5″ plank, and for plank wider than 5 inch, stagger as much as possible with minimal or no H joints. See Figures 8-1 and 8-2.

8. To minimize expansion on floors wider than 20 feet, more or less spacing between rows may be needed, depending on geographical area, interior climate control and time of the year.

9. Where spacing is required: Use a washer or removable spacer to leave additional space every few rows and/or start in center of room and work out to both sides. Do not use spacers that may cause damage on factory-finished products.

10. Nailing: Blind-nail through the tongue using 1 ½” to 2″ fasteners. Use 1½fasteners with ¾”plywood subfloor direct to concrete slab. Face-nail boards where needed using 6d-8d casing or finish nails. Fasteners should be spaced every 6-8on blindnailing, or every 10-12on face-nailing.

11. If adhesive is used with nailing, follow wood and/or adhesive manufacturer’s instructions for installing plank flooring.

12. Blind-nail, face-nail or use wood floor adhesive, as necessary, to complete the final rows.

F. Center Line Layout

Note: For instructions on using the trammel point method to square a room and find the center point, see Appendix G, Trammel Point Method.

1. Find the center of the room, measuring off the two longest walls, and snap a line down the center of that room.

2. Install a starter board on the line. Fasten the starter board to the floor using wood screws.

3. Nail the first row of wood flooring against the starter board, being careful not to move the starter board when nailing. The groove of the flooring should be against the starter board.

4. Use a blind nailer to install the remaining rows of wood flooring. Use the nailing practices described earlier in the chapter.

5. After installing in one direction, remove the starter board and start rows going in the opposite direction.

6. Install a spline or a slip tongue in the groove of the board that was against the straightedge. Put wood flooring adhesive down the entire length of the groove before installing the splines.

7. Install the spline using a blind nailer. To keep the spline in alignment for the next flooring board, use a scrap piece of wood flooring to run along the length of the spline as you nail.

8. Install the remaining rows in the opposite direction. Use the nailing practices described earlier in the chapter.


Coefficients of Change: How Moisture Affects Wood Flooring

At 70 Fahrenheit, a relative humidity of 25 percent gives an EMC of 5 percent, and a relative humidity of 75 percent gives an EMC of 14 percent. A 50 percent variance in relative humidity produces an EMO change of 10 percent. How that affects wood flooring depends on which species is being used. However, let’s say the width variation is just 1/16″ for a 2.” board. That’s a full inch over 16 boards in a floor. Over the width of a 10-foot wide floor, that amounts to more than three inches of total expansion or contraction. Protective coatings cannot prevent wood from gaining or losing moisture; they merely slow the process. Installers need to take those expected dimensional variations into account when installing the wood flooring.

This is a tool for the wood flooring professional to calculate perpendicular movement, but not absolute due to variable conditions. These variables need to be taken into consideration when calculating dimensional change coefficients (e.g., plain sawn dimensional change vs. rift sawn dimensional change, etc.). These figures are noninstalled boards.

The following is a simple way to determine the number that will be used to calculate dimensional change coefficient for any given species:

Examples:

Species type: (example only) Lapacho/Brazilian Walnut

Average reported shrinkage value (green to oven dry): Tangential 8.0%

Coefficient is determined by taking the tangential shrinkage and dividing it by the fiber saturation point. (To find the fiber saturation point, google the species.)
Answer: .8/20 = .004 coefficient

A red oak (change coefficient = .00369) (see page 6 of NWFA Technical Publication A100, Water & Wood) board 5 inches wide experiences a moisture content change from 6 to 9 percent – a change of 3 percentage points.

Calculations: 3″ x .00369 = .01107 x 5 = .055 inches

In actual practice, however, change would be diminished in a complete floor, as the boards’ proximity to each other tends to restrain movement.