The first step of preparation of the subfloor is to determine the moisture content of the system. The subflooring moisture content should be no more than four percent higher than the average moisture content of the geographical area. (See FCI article on Acclimation)
o Check the subfloor for correct nailing, set any raised nails and add nails/screws necessary to secure panels. This helps minimize issues associated with noisy and loose flooring.
o Check the flatness of the system. All deviations from flat should be gradual. Lower humps and raise low areas. This can require the framer to cut joists or add spacers. For nail down flooring, 3/16-inch in 6 feet is the standard; any greater variation should be discussed with the customer. Flooring may not conform to a greater variation, and noisy flooring or movement between boards may result. For adhesive applied flooring, 1/8-inch in 6 feet is the maximum variation for good adhesive performance.
o Clean the subflooring of debris such as drywall compound, caulk, and other foreign objects. This may require sanding the subflooring.
o Check edges of subflooring for flatness. Sand all raised edges flat with an edger.
o For solid T&G flooring, installation mark all joist lines on the wall for location of face nails along starting and finishing runs.
o For solid T&G flooring, installation roll out #15 felt along starting wall. Continue felt overlapping edges 2-3 inches across room.
o Under cut with a jamb saw all door casings and door trim so that flooring will slide under and show no gaps after installation.
o Check for layout and determine longest and straightest continuous run for starter. Measure across rooms to determine square. Square rooms with starting line and position string line for starting run. Recheck measurements before installing starter run.
o Appropriate expansion should also be provided between subfloor panel edges and at panel ends (1/8-inch). For square edge plywood cut an expansion gap of 1/8-inch around plywood edges if gapping is not present.
The first step with slab construction is to check the slab for moisture. The temperature and relative humidity must be near occupied conditions for the tests to give good results. For adhesive installed flooring check with adhesive manufacturer for recommended moisture test and acceptable levels of moisture. For the calcium chloride test, a measure of 3 lbs or less is considered acceptable for wood flooring application. The slab must be clean, dry, and flat.