Adhesives have improved in that they are more environmentally friendly, are very water resistant when cured and have good grab. One thing that has changed over the years with multi-purpose adhesives is that when they became environmentally friendly, solvents were removed and water was added. This means that if you have a slab that has a higher moisture moisture vapor emission rate, the adhesive doesn’t cure up like the adhesives of years ago with solvents. With moisture cured urethane adhesives that are used for glue down of wood flooring, you have just the opposite; the adhesive sets up and cures too soon, causing bonding issues as well as moisture issues.

So if we have all these improvements with technology, why then such high failure rates? One big factor that the flooring installer and flooring contractor has no control over is a vapor barrier beneath the slab. Without a vapor barrier properly placed underneath the slab, it’s a roll of the dice whether the flooring will succeed or fail due to moisture issues. Even with a vapor barrier placed under the slab it must be properly installed, which means that the cement finisher does not puncture the membrane. Penetrations such as pipes that come through the slab must be properly addressed, and the right membrane must be used. There are membranes that break down over time, which is why even with a membrane that was placed on the original pour, there can be failures years down the road due to moisture. The concrete industry has had controversy over the years as to whether the membrane goes directly beneath the slab, a blotter layer placed between the slab and the moisture barrier, or placement of a barrier at all. So if a barrier placed beneath the slab is going to minimize flooring failures, why doesn’t every slab have a barrier? There are reasons for that: local building codes, no specification calling for a moisture barrier, finishing issues with concrete curling; these are a few. What makes this a big headache and a costly one for the flooring industry? The installer or flooring retailers are being held accountable for moisture-related failures when they had nothing to do with the placement of the concrete. They are being forced to perform moisture testing without the required proper conditions, which in reality voids the test results.

Because of all these moisture issues, the flooring industry continues to evolve products available from fairly

inexpensive to very expensive. Do they work? Yes. Have they all had a failure? Yes. There is not a product made that is completely failsafe without the proper barrier placed beneath the concrete at time of placement. Let’s take a look at the products that are being used to minimize moisture intrusion in concrete. First you have moisture retarders; these types of products slow the movement of moisture vapor emissions coming up through the slab. These products are not moisture barriers, meaning they do not stop moisture movement; they slow the movement of moisture vapor emissions from a concrete slab. The next step up from moisture retarders is moisture barriers. These products have the ability to stop moisture vapor emissions from emitting from a concrete slab. Silicate-based moisture barrier products have been used for years with mixed success. Silicate based products are reactive type products, meaning they react with another chemical (calcium hydroxide) that is in the concrete matrix. When these products react with each other, they form a gel (calcium silicate hydrate), block the capillaries or voids in the concrete and then harden. Silicates are penetrants, meaning they go into the concrete to form a barrier; how deep depends on the density and the permeability of the concrete. This type of product is less expensive, but does not have the success rate as the products we will discuss below. Bone Dry is an example of a Silicate type product. These products are also known as concrete hardners.

Sealers are products that do not penetrate into the concrete but seal the surface; polyurethanes and epoxies are sealers. Epoxies are costly but have a good success rate when properly applied. There are two different types of epoxy sealers. One, the epoxy sealer is placed directly on the concrete slab with little to no prep.

Anderson Duck Shield, Armstrong VapArrest, DriTac 7000, and Sika Primer MB are examples of this type of epoxy sealer. A urethane adhesive must be applied over these types of coatings. The second type of epoxy sealer, requires a profiled (shot blasted) concrete surface. Next, the layer of epoxy coating is applied using a wet film gauge to achieve proper coverage of material. This is usually followed by a sand broadcast or the use of a primer to receive a self leveling underlayment. The sand broadcast or the primer is necessary in order for the self-leveling underlayment to bond to the epoxy coating. Mapei Planiseal EMB is an example of this type of epoxy sealer. It is good up to 25-lbs. moisture, per the Calcium Chloride test.

The hardwood industry has had a product for several years that were troweled onto a concrete slab. Once the product is troweled on, the product flows together to create a membrane. Once the product has dried, a moisture cured urethane is applied over this membrane to install the wood flooring. There are now adhesive products that can be applied during the installation of hardwood flooring that create a moisture barrier. These adhesives are trowel on and flow together much like the membranes described above. These products are known as All-In-One products. The two-in-one products are a moisture barrier and adhesive in one. A four-in-one, what they are stating is that it is a moisture barrier, adhesive, crack isolation barrier (typically up to 1/8″ horizontal plane), and sound deadening product.

Anderson enSURANCE 3X Options, DriTac 1001 and SMC, Mapei 995 and 985 are examples of these types of Adhesive products. One thing an installer/contractor needs to make certain: know your products, and work with the manufacturer of the product to assure the correct application of that product.