Before beginning any job it is important to evaluate the job site to ensure it is suitable for flooring installation. Begin the evaluation outside. The biggest concern is rain water management. Whether the home is on a slab, a crawl space or over a basement, it is critical to keep as much water as possible away from the foundation. If the soil becomes saturated with water, it can penetrate the foundation walls or rise through the ground surface into the foundation or crawl space.

Outdoors

Check for properly installed, clean, working gutters, with down spouts and spill guards that direct the water away from the foundation by several feet and down hill. Look for spouting that has over flowed by checking the ground beneath them. Check the landscaping. With new construction, the final grade should be completed. The soil should be sloped away from the building structure. Rule of thumb is ½” per foot for at least 6 feet. Look for things like raised flower beds, heavy shrubbery close to the foundation walls, and cracked or broken driveways. Is the driveway slopped away from the house? Lawn sprinklers should be directed away from the foundation walls. Look for discoloration, mold or mildew on the foundation walls.

Crawl spaces

Wooden subfloors constructed over a crawl space MUST have adequate ventilation. Crawl space should be a minimum of 18″ from the ground to the bottom of the joist. 18″ of clearance beneath duct work is a requirement. The ground should have 100% coverage with a vapor retarder of 6 mil minimum black polyethylene. Seams should overlap at least 8″ and the film should run up the wall at least 6″. In cases where a thin concrete slab is covering the ground a vapor retarder should still be installed beneath the slab. The crawl space should have perimeter venting equal to 1.5% of crawl space square footage. In other words, 1,000 square feet of space would have 15 square feet of venting. You are looking for good cross ventilation with no dead air space. In some areas of the country a closed crawl space is preferred. To function properly a supply and return air should be included in these spaces. Always follow local building codes. You have to actually look in and check crawl spaces. Is there standing water? Excess moisture in the crawl space can affect subfloors and have a negative affect on the subfloor and flooring.

Concrete slabs

All concrete slabs must be tested for moisture. There is no way to tell if the slab is properly constructed with a vapor retarder separating the concrete from the ground. Converted garages and rooms that were not originally intended to receive finished flooring will not have a vapor retarder beneath the slab.

Moisture measurements for concrete subfloors must not exceed the manufacturer’s recommendation. Some manufacturers accept meter readings, Calcium Chloride tests, and some require the RH Probe test. Be sure to record the measurements for future reference. New concrete must cure for at least 60 days and then be tested.

Indoors

Basement floors and walls should be dry. Look for signs of mold, mildew or alkalinity. Check items lying on the floor for moisture. Is there a musty smell? Is the HVAC in place and working? The HVAC system should be operating for at least 2 weeks prior to installation. It is best to install any floor in an environment that’s as close to normal living conditions as possible, 60° F to 85° F and 35% to 75% RH. Record the temperature and relative humidity. Hygrometers are inexpensive and invaluable. Again, record your test results. Check for subfloor flatness. Generally, 3/16″ in 10 feet is required although each manufacturer’s numbers may vary a little. Flatness can be checked with a straight edge, laser level, or string line. Even if a loose-lay/floating floor is being installed, this is critical. These types of floor are not made to cover wavy or uneven subfloors.

Always check the instructions for the floor you are installing.

Suspended Wood Subfloors

What type of subfloor is it? OSB, plywood, or particleboard? Know what type of subfloor you are going over. Is carpet covering the subfloor? Pull a corner up, or go down to the floor underneath and look up to see what the subfloor is. How thick is the subfloor? This is usually stamped on the under side of the subfloor panel. Make note of the joist direction and spacing.

Measure and record the subfloor moisture content. Own a moisture meter and know how to use it. For loose-lay type floors (vinyl/laminate/hardwood/cork/ceramic), the moisture content of the wood subfloor should not exceed 13%. If the subfloor exceeds 13%, chances are that when the home or building goes through it’s first heating season, the subfloor will shrink (dry out) more than the flooring structure can handle.

Existing Flooring

How many layers of existing flooring are down? Is it fully adhered, perimeter adhered, or loose lay? How old is the flooring? Does it contain asbestos? These are things you will need to know. You can not install any floor over a perimeter adhered resilient floor.

Documentation

Document and record all of your observations and test results with notes and pictures and put them in the job file. Digital cameras work well and most record the date when the picture is taken. Most people have a camera on their cell phone. Some things may not seem very important, but it only takes a second to look and it’s good to get in the habit of writing everything down. Good notes are very valuable when a problem pops up. These notes will be valuable to your installation crews while out on the job site.