The latest consumer trend today is wide plank hardwood flooring…my wife included. Along with the consumer demand is increased installation issues with these wide width products. The chance of cupping with these products is greater than that of a 21⁄4′′ or 31⁄4′′ wide hardwood product. When installing these products, there are certain precautions that must be taken to help reduce the chance of hardwood cupping.
Let’s break this down into two categories; 1) Solid Wide Width Plank and 2) Engineered Wide Width Plank.
Solid Wide Width Plank
Before nailing/stapling down the first plank, there will be a number of steps that need to be taken to help ensure a successful installation.
The installation of solid wood flooring should be postponed until all moisture producing trades (masonry, drywall, plaster, painting, etc.) are complete and their work is thoroughly dry; the roof, windows and exterior doors are installed tight and dry.
Permanent air conditioning and heating systems should be in place and operational. The installation site should have a consistent room temperature of 60°F – 80°F and humidity levels of 35% – 55% for 14 days prior to and during installation and until occupied.
Check and document moisture content of the subfloor with the appropriate moisture test. The moisture content of the plank flooring should not differ from the moisture content of the subfloor by more than 2% – 3%. The wood subflooring must not exceed 12% – 13% moisture content as recommended by the hardwood manufacturer. Once both have reached the desired range, installation may proceed.
Proper Crawl Space – Before installing over a crawl space, do your homework to make sure the crawl space meets the requirements. Crawl spaces must be a minimum of 18′′ from the ground to the underside of the 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. Where necessary; local regulations should prevail. Please note, the subfloor must not exceed 12% – 13% moisture content as recommended by the hardwood manufacturer.
Some manufacturers are recommending Glue Assisted Nailing or use of a moisture retarding paper such as 15-lb. roofing felt or Aqua Bar B. Glue Assisted Nailing is when you apply a bead of premium grade urethane construction adhesive such as Mapei 905 Moisture Cured Urethane Construction Adhesive (item #MAP92619), applied in a serpentine pattern to the back of the hardwood (shown below) before nailing the plank into place. What is the benefit of Glue Assisted Nailing? With the addition of a urethane construction adhesive, you can reduce the chance of seasonal distortion such as cupping and shrinkage. You cannot use both the urethane construction adhesive and the moisture retarding paper together. Please note, Common Brown Kraft Builder Paper and Red Rosin Paper generally do not qualify as vapor retarders.
The nailing pattern will be tighter with a wider plank:
Engineered Wide Width Plank
The environmental and crawl space requirements for Engineered Hardwood will be the same as the ones listed above under the Solid Hardwood. The only difference is that the moisture content of the engineered plank flooring should not differ from the moisture content of the subfloor by more than 4%. The wood subflooring must not exceed 12% – 13% moisture content as recommended by the hardwood manufacturer. Check and document moisture content of the subfloor with the appropriate moisture test. Once both have reached the desired range, installation may proceed.
With wide width Engineered Plank Hardwood, you have two methods of installation:
Staple or Nail down
I have seen both systems used with very good success. In the builder market, most installers are gluing the product down to the subfloor regardless if it is wood or concrete subfloor. They are using a urethane wood adhesive rather than nailing down the product because of the installation and call back issues they encounter with nail down. By gluing the product down, you have adhesive covering 80% – 90% of the back of the Engineered Plank to help hold it.
In renovation work, most product is staple/nail down over wood subfloors. When stapling/nailing down, you only have the fastener holding the edge of the board down. Regardless if installing a 3′′ wide Engineered Hardwood or a 5′′ wide Engineered Hardwood Plank you are not using any more fasteners despite the increased width. The fastener spacing on both widths should be every 3′′- 4′′. When stapling/nailing down, I strongly recommend the use of a moisture retarding paper such as 15-lb. roofing felt or Aqua Bar B.
Some hardwood manufacturers recommend to apply a bead of recommended wood glue (Armstrong EverSeal or DriTac 8100) to all of the end grooves regardless if gluing or nailing down on products greater than 31⁄4′′ wide.