How to Account for Expansion Space During Installation

The Dimensional Change Coefficient and accompanying calculations in the Moisture and Wood publication and in the Installation Guidelines give you the tools necessary to predict approximately how much expansion to expect in solid wood flooring if, or when, the flooring gains moisture after installation. We are beginning to see more architects and builders specifying flooring installed tight to the walls, without baseboard, otherwise known as “net-fit installs.” The following are three options to assist with necessary expansion space during the install:

  1. Undercut the abutting material to ensure adequate expansion space.
    For example, undercutting drywall or plaster may allow you to gain 1/2” of expansion without being concerned with the thickness of the baseboards. Undercutting any abutting material takes time, and must be accounted for in the overall job cost.
  2. Use cork or elastomeric caulking.
    Cork and elastomeric caulking are resilient materials that will slightly compress when the wood expands. Taking this into account can help compensate for voids and necessary expansion. However, there are variations in the density of cork and elastomeric caulking products, and they will never compress to zero. Never use these products as a substitute for the required expansion space. Always take into account the required expansion space during the installation and compensate as necessary.
  3. Strategically place internal expansion into the wood floor.
    This is also known as using washer rows within the floor. This is a method used where you purposely leave gaps in the floor using spacers (washers or string trimmer line) to accommodate for expected moisture gain. This is very common in gym floor installations, primarily due to the expanse of the entire floor and the uncontrolled conditions of the space from season to season.


One thought

  1. Are spacers required in an in home installation of 3/4″ solid 3.25″ wide red oak. The temperature in the house ranges from 68 (nightime sleeping) degrees to 76 degrees (dead of summer air conditioned). The room is 20′ wide by 40′ long. Boards are running the long way. My installer is rwxommending spacers every 4 ft but i do not want to see gaps. The wood has been stacked up in the room for three weels prior to installation. We will leave .75 inch around the perimeter.

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