Hardwood Floors December 2017/January 2018

AT THE SITE

Installing Wide Plank Floors (Continued)

As a general rule of thumb when racking plank flooring follow these guidelines: In general, try to stagger as much as possible with minimal or no H joints and no stair-stepping pa erns with plank oors. A empt to stagger end-joints of boards row to row a minimum of twice the width of the ooring. For example, 8” minimum stagger for 4” planks, 12” stagger for 6” planks. Although this is ideal, many wide plank ooring products will not allow for such a wide stagger due to the amount of shorter boards.

Some common installation methods not addressed in the current Installation Guidelines include use of adhesive over wood subfloors, whether as a glue-assist application or full spread application:

Glue-assist, or using adhesive in conjunction with using fasteners, is a common installation method in many markets over wood sub oors. ings to note when using this installation method: • is installation method doesn’t require the use of a traditional vapor retarder over the sub oor, which enables the glue to stick to the wood sub oor rather than the paper. • In order to alleviate the vapor retarder, it is necessary that any moisture fromwithin or below the sub oor is at the same level as above the oor space before, during, and is maintained post-installation. • Another option when the conditions below the substrate cannot be controlled is to use a liquid-vapor retarding membrane compatible with the adhesive and the sub oor. e perm rating of the membrane should be greater than 0.7 and less than or equal to 10 per NWFA Guidelines. • e nailing schedule should remain the same as normal installation for the plank ooring being installed. Full spread direct glue installations over wood sub ooring may be appropriate in some situations. e critical factors to take into account include compatibility of the adhesive and the sub oor, and the identi cation of any moisture-related issues below the sub oor (crawlspace or basement). If the relative humidity below the sub oor is elevated, the space is unconditioned, or moisture in any form is present, full spread adhesive application or use of any type of ooring moisture control systemwith a perm rating less than 0.7 should not be used. e reasoning is simple: • A fundamental principle in nature is for materials in vapor form to seek equilibrium. Materials that are higher in concentration in one area will disperse to areas of lower concentration. is process is called vapor di usion. Cooler air in unconditioned crawlspaces and un nished basements inherently has higher relative humidity levels and will naturally nd its way upward, through the sub oor and wood oor, into the warmer, drier air within the living space. An intact vapor retarder is designed to slow this moisture migration, but not stop it. • When covering the wood sub oor with a moisture control system that blocks this moisture such as an impermeable membrane, the potential for this moisture to become trapped in the sub oor becomes greater. According to the Environmental Protection Agency, these types of vapor barriers can prevent damp or wet building materials from drying quickly enough to prevent mold and fungal growth…potentially leading to rot. • Wood sub oors can rot when exposed to long-termmoisture. is is caused by a wood-destroying fungi that a ack and eventually disintegrates the wood bers within the sub oor material.

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ere are many installation practices that professionals in our industry use every day. e NWFA Installation Guidelines were developed by our industry to ensure successful installations with all types of wood oors. Because wide plank ooring has become the most common product sold and installed today, the evolution of our guidelines will continue to explore the many methods used to install them. We also must ensure the installed ooring we put in today will last hundreds of years to come so that the future generations can discover and restore the buried treasures we leave behind.

Brett Miller is VP of Education & Certification at the National Wood Flooring Association in St. Louis. He can be reached at brett.miller@nwfa.org.

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