Wood Sub-Floor Preparation

Wood sub-floors are a great surface for instantiating wood flooring, and the only choice for thick solid wood. Preparation of the sub-floor is very important in order to succeed the installation. We must agree that the foundation must be solid. Three main areas of concern: structural integrity, a clean, flat and even surface, and moisture content. We present a list of tasks you need to be concerned about.
Structural Integrity

The quality of your floor depends a lot on the integrity of your sub-floor. You need to do a visual check of the surface, after the floor is swept. Countersink any nail or screw heads. Replace any nails which cannot be leveled and countersunk.

Walk on the floor and listen for squeaks in order to feel for locations that are spongy or feel hollow. This indicates a weak spot which should be addresses before further proceeding. Screw or nail down any loose boards.

Note: The general recommended thickness for the sub-floor is ¾”. Discuss this problem with the manufacturer and make sure that your sub-floor meets all requirements.

A great deal of damage to the floor or facts which not meet the manufacturer standards, would probably make you call in a professional contractor to replace the entire sub-floor.

Flat and Even

Sub-floors should be within a tolerance of 3/16 of an inch over a span of 8 to 10 feet. Within any 8 –10 foot range, there should be no dips or humps which exceed 3/16 of an inch. Lay out a flat 8 – 10 foot plank and mark trouble spots as you move it across the floor in all directions.

Minor hump problems can be fixed with a hand-held or rented orbital sander. Be sure to wear protective goggles and a dust mask because sanding throws up a lot of dust.

Fill dips, low spots and gouges with a cementitious leveling compound, which may also be called floor patch. The first step is mixing it according to manufacturer instructions. Add the water first and then the dry mix so you won’t get a thick clump in the bottom which should be about the consistency of pancake batter. In order to apply floor patch evenly, take the board you’re using as a straight edge and pour the amount of patch to fill the gap. The next step is pulling the board back and forth over the area in order to spread the patch. in order to apply equal pressure, one person should be on each end of the boarder. As long as it’s even it the process was executed good enough. This is called screeding. Now check if it’s flat, and sand if necessary.

Note: Do not use large areas of floor patch if you’re going to be nailing or stapling the wood flooring because it can crack.

Moisture

Usually, wood sub-floors are installed over concrete slabs. The concrete is a porous material that pulls moisture from the air and ground. Now keep in mind that this is the reason why solid wood floors should not be installed at or below grade, or sea level. Too much moisture will soak into wood planks, causing them to swell. Too much moisture causes the boards to push beyond the small area allocated for movement, and the floor becomes pressurized as the boards crowd the space. In the end, floorboards with too much moisture result in buckling and warping.

A moisture test kit should be used to ensure that the concrete and the wood sub-floor meet the recommended moisture content specified by the manufacturer. This is usually no more than 4%.

You should use an underlayment with a moisture barrier, or 2-in-1 underlayment, unless you are in an area with very low humidity. Underlayment comes in rolls and generally, you would roll out strips of underlayment to cover the entire floor and then join the edges of each row with a special tape.

After everything is done, you should clean the floor, removing spatters of compound, dust, nails, or anything else that may cause problems. Wood flooring is an investment since it improves the value of your home.

Check the manufacturer instructions for every step of the way.