Over this, apply a second similar coating of mastic and roll out a second layer of asphalt or paper in the same direction as the first, staggering the overlaps to achieve an even thickness. Polyethylene: Cover the entire slab with 4 to 6 mil polyethylene film, overlapping the edges 4" to 6", and allowing enough film to extend under the baseboard on all sides. When moisture conditions are more severe, prime the slab and apply cold, cut-back mastic with a straightedge or fine-tooth trowel sq.
Lay 4 to 6 mil polyethylene film over the slab, overlapping the edges 4 to 6". In either case, roll the film flat or "walk" it in, stepping on every square foot to ensure adhesion. Puncture bubbles to release trapped air. Install the plywood after the vapor retarder is in place. Lay plywood diagonally across the direction of the finished floor to help prevent cracks along panel edges. Do not use power-actuated fasteners or concrete nails when radiant heat pipes are embedded in the slab.
Lay panels in a staggered pattern with at least 2' long planks along starting and finishing walls. For systems other than radiant heat, the plywood planks may be glued to the plastic with asphalt mastic. Floating subfloor of 2 layers of plywood secured together over a vapor retarder. No fasteners penetrate the retarder or the concrete. Sleepers Flat, dry, kiln-dried, preservative-treated 2" x 4" sleepers in random lengths 18" to 48" can also serve as a nailing base.
Otherwise, yellow pine, fir or other kiln-dried framing species is acceptable. Begin by sweeping the slab clean, applying an asphalt primer and allowing it to dry.
Before installing the floor, loosely lay an additional vapor retarder of 4 to 6 mil polyethylene film over the sleepers, overlapping the edges on top of the 2 x 4s. Avoid bunching or puncturing the film, especially between sleepers. This method requires you taping a inch square piece of clear plastic, at least 6 mils thick to the floor. Lay the section on the concrete slab and use moisture-resistant tape to tape all four sides to the floor. You do this in three to four areas around the slab.
Leave it for 24 to 48 hours. If you see signs of moisture or condensation on any of the plastic, you likely have a problem, but you can never be sure how big, or what it is, or exactly how much moisture there is. The calcium chloride test measures the surface moisture of the slab. You can see the kit and how it works in this video. Humidity sensors or moisture meters require drilling holes and inserting probes to measure the amount of water.
Some meters measure results in pounds of water per 1, square feet of the floor during a hour period. Other meters can measure relative humidity in the slab. One very accurate testing method is to use the Wagner Rapid R. Most flooring manufacturers say you should not install hardwood over concrete if the tests show the moisture emission rate is over 3 pounds.
When installing hardwood flooring on basement , the concrete must be flat so the tongue and grooves of the hardwood meet and connect. Old basement slabs can crack and buckle in places. You need to fill any large cracks and be sure that the entire floor is level. That means pouring a thin layer of cement to fill in dips and gaps. Here is a short video to show you how to level a concrete floor. To check the evenness of the slab, use a 6-foot or longer straight edge.
You may have to cut one utilizing a table saw to ensure straightness. Lay the straight board on the floor and place a level on top. Concrete is very porous like a sponge. Water can quickly pass through it causing moisture problems, especially below grade. Typically, it is sheets of plastic laid on the slab and taped at the seams with waterproof tape.
Watch this video to see how easy it is:. He adds an optional underlayment on top of the moisture barrier for sound reduction. There are other moisture barrier options. Ask your flooring professional what he or she uses.
A subfloor is the floor surface directly under the hardwood floor. In this case, the subfloor is the concrete slab. Wood needs to move as the humidity increases and decreases throughout the year. For these reasons, you should avoid gluing, nailing or permanently attaching directly to the slab. It adds a lot of extra time and effort. It lays directly on top of the waterproof barrier, or combination of barrier and underlayment, to help cushion and insulate.
Be aware of the additional height that the subfloor and underlayment add. They can add up to two inches in a basement that may already have a low ceiling. There are many options for building a plywood or OSB subfloor. This video demonstrates a cost-effective method for DIYers. Unfortunately the explosion of manufacturers in recent years trying to stimulate sales of solid wood floors on concrete created a plethora of problems, namely by inexperienced installers and salespeople.
Reasons include better stability which translates into fewer problems and no need for a plywood nailing base. The sleeper system that entailed fastening 2' X 4's to the concrete laid on their side has faded from use. While the sleeper on slab application is rarely used today, it created vertical height concerns. This can cause problems with exterior door entries and other fixed objects.
A variety of fasteners are used, including masonry cut nails, tapcons concrete screws , and Hilti types. Methods vary from one region to another, or what professionals are accustomed to. Update - The above procedure is losing credibility due to the loss of moisture protection through direct fastening. Read more. Plywood is installed opposite of one another, overlapped at the seams, then stapled or screwed together with shorter fasteners.
You will also want to leave a small half-inch gap between the flooring and wall. Reinstall your baseboards and trim , then clean up the room. Be sure to take a moment to admire your work. Let us teach you how to select the best hardwood floors for any home. This post was originally published on December 15, It has been updated for clarity. Close Menu Home. You will need a barrier that is appropriate for the flooring you choose: Floating Floors — Typically, these moisture barriers are made from plastic.
Nailed Floors — You will need a moisture barrier that protects the subfloor as well as the flooring. Glued Floors — A heavy coat of moisture barrier will be required since the flooring is glued directly to the subfloor.
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