5/16″ and 7/16″ Solid Hardwood has been a product that I have had several calls on this summer. All the calls were moisture related. In every case, the installer checked the subfloor for moisture and was well within the recommended limits, only to have a moisture problem down the road. Remember, moisture testing is only measuring moisture at the time of the testing. It is not a long term predictor of what moisture problems may occur later on.

I have had calls on these products buckling off the floor when glued down and when mechanically fastened. These products are very sensitive to moisture and will expand in the width until they can go no more and then they lift off the floor. The other problem is that installers do not allow for the proper expansion zone required with these products.

For glue down installations on concrete, I strongly recommend the use of a Professional Moisture Retardant System as recommended by the hardwood manufacturer. If excessive moisture is present or anticipated or something out of the ordinary happens, the use of one of these products could eliminate potential issues with you and the home owner.

For these reasons, I will cover the proper installation of these products over both concrete and suspended wood subfloors and also keeping the warranty with the manufacturer.

Required Expansion Zone for Glue Down and Staple Down;

Armstrong/Bruce – Allow 1/2″ expansion space around all vertical objects.
BR111 – Allowing 1/2″ expansion space around all vertical obstructions is critical.

For glue down installations on concrete, I strongly recommend the use of a Professional Moisture Retardant
System as recommended by the hardwood manufacturer. If excessive moisture is present or anticipated or something out of the ordinary happens, the use of one of these products could eliminate potential issues with you and the home owner.

Concrete Subfloors

Armstrong/Bruce 5/16″ Solid Hardwood is recommended on-grade and suspended concrete only, not below grade.

Concrete Moisture Tests
NOTE: Test several areas, especially near exterior walls and walls containing plumbing. All concrete subfloors should be tested, and results documented, for moisture content. Visual checks may not be reliable. Note; moisture testing is only measuring moisture at the time of the test. It is not a long term predictor of what moisture problems may occur.

Armstrong/Bruce Acceptable test methods for subfloor moisture content include:
•    Calcium Chloride Test (ASTM F 1869): The maximum moisture transfer must not exceed 3 lbs./1000 ft.2 in 24 hrs. with this test.

Prior to testing with the Tramex Concrete Moisture Encounter, the actual test area shall be clean and free of all foreign substances. All residual adhesives, curing compounds, sealers, paints, must be removed. Failure to do this will result in inaccurate readings.

* Expose (abrade/grind) a minimum area of 20 inches by 20 inches. Check three test locations for areas up to 1000 ft2, and add one additional test for each 1000 ft2. Check areas around the outside walls for possible moisture.

All concrete should be tested, regardless if it is on grade or suspended.

After exposing the concrete, press the On button and place the Tramex Concrete Moisture Encounter on the floor. The Power/BAT light will be blinking. Press down on the Tramex Concrete Moisture Encounter to obtain your reading.

Moisture readings should not exceed 4.5 on the upper scale.

Prior to applying any moisture retardant system or adhesive, ensure that the concrete subfloor is free of any sealers or curing compounds. This may be accomplished by sanding/grinding the concrete subfloor.

* Warning—Do not sand, dry sweep, dry scrape, drill, saw, beadblast, or mechanically chip or pulverize existing resilient flooring, backing, lining felt, or asphaltic cut-back adhesives. These products may contain either asbestos fibers or crystalline silica. Avoid creating dust.

Armstrong/Bruce Moisture Retardant Systems
If excessive moisture is present or anticipated, use Armstrong VapArrest™ S-135 Professional Moisture Retardant System. NOTE: When using Armstrong VapArrest S-135 Professional Moisture Retardant System retardant, USE ONLY Armstrong EverLAST™ Premium Urethane Adhesive. Remember, to receive the guaranteed installation warranty, you must use Armstrong EverLAST Premium Urethane Adhesive.

Armstrong VapArrest S-135: Apply the materials after all subfloor preparation is complete. Follow the instructions on the VapArrest S-135 label. Allow 8-24 hours curing time before application of the hardwood flooring.

BR111 5/16″ and 7/16″ Solid Hardwood is recommended on-grade and suspended concrete only, not below grade.

Warranted Moisture Sealer Products
The following are sealer and glue systems that offer a warranty from their manufacturers for subfloor moisture intrusion. BR-111 highly recommends the use of these products when gluing down the 5/16″& 7/16″ solid hardwood flooring. Due to the ever changing moisture vapor emission from concrete subfloors, it is HIGHLY RECOMMENDED that these products be used.

Recommended Moisture Retardant Systems (Subfloor moisture intrusion warranty provided by their manufacturer)
– Bostik MVP (Moisture Vapor Protection) used to seal the subfloor along with the use of a Bostik
Moisture Cured Urethane Adhesive. See website www.bostik-us.com for details.

– Sika Primer used to seal the subfloor along with the use of Sika T55 Adhesive. See website www.sikausa.com for details.

– DriTac – MCS 7000 Concrete Moisture Control used to seal the subfloor along with the use of a DriTac
7600 Moisture Cured Urethane Adhesive. See website www.dritac.com for details.

BR111 Acceptable test methods for subfloor moisture content include:
•    Calcium Chloride Test (ASTM F 1869): The maximum moisture transfer must not exceed 3 lbs./1000 ft.2 in 24 hrs. with this test.

Staple-Down Installations over Suspended Wood

Both Armstrong/Bruce and BR11 require the use of a 6 mil poly installed over the suspended wood subfloor. This step is usually left out on installations.

Crawl spaces must be a minimum of 18″ to 24″ from the ground to the underside of joists. A ground cover of 6–20 mil black polyethylene film is essential as a vapor barrier with joints lapped 6″ and sealed with moisture resistant tape. The crawl space should have perimeter venting equal to a minimum of 1.5% of the crawl space square footage. These vents should be properly located to foster cross ventilation (see below). Where necessary, local regulations prevail.

Armstrong/Bruce
Installing the Moisture Retardant Barrier (Staple-Down Installations)
CAUTION: The moisture retardant barrier may be slippery and unstable when walked on prior to the installation of the flooring. Use extreme care during installation.
•    Roll out the materials in the same direction the flooring will be installed, allowing the moisture retardant barrier to extend 3″–4″ up the walls.
•    Position the moisture retardant barrier so the chalk lines can be seen through this material.
•    Staple or tape at the corners to hold the moisture retardant barrier in position.
•    Overlap the moisture retardant barrier 6″ at all joints and poly tape the seams together. The first piece of
moisture retardant barrier will be secured when the first row of flooring is installed.

BR111
The 6 mil poly should have joints overlapped 18″ and taped together. In the case of a staple-down
installation, a 6 mil poly barrier must be established above the wooden subfloor and under the hardwood floor.