The big box expert has led you down the paint aisle after you inquired about sealing your concrete slab. You didn't know any better, the handyman said you needed a $25.00 gallon can of sealer for your hardwood glue down project.
See The Big Red X?
These products are not to be used for sealing concrete floors if you plan any glue down direct application. Yes, they can be used for floating floors that do not come into contact with the concrete, but we recommend the use of sheet plastic (visqueen) moisture barriers regardless.
Older Moisture Sealing Methods
Up until the early part of this century many of us never saw sealers that were manufactured in tandem to be used with actual wood flooring adhesives. Prior to that period, if any high moisture readings were present, solutions were typically the installation of sheet vinyl before the actual glue down installation. While vinyl is still used today, if you plan on using the system, it is vital to be aware of the hardwood flooring adhesive properties.
Before the wide spread use of urethane adhesives, vinyl moisture barriers could be installed with common adhesives used to install any vinyl floor. Urethane adhesives changed that because of their strength. Using an ordinary latex adhesive in this scenario with a urethane based wood glue will likely result in de-bonding of the vinyl from the concrete.
Proper Sealers For Concrete
Today, manufacturers such as Bostiks, Mapei, and Sika to name a few, offer their own sealer variations to be used in conjunction with their own urethane wood adhesives. Ordinarily a 24 hour waiting time is required after the sealer application with any new glue down installation. Some sealers also provide sound deadening properties.
Installation procedures call for either troweling (depends on manufacturer) to the subfloor similar to applying the wood floor glue, or applying with a paint roller. Products do not come cheaply. The actual wholesale cost of the Bostiks MVP (shown right) runs round $ 145.00 per five gallon container. Add in the dealer markup and one can easily be spending $ 225.00. Each five gallon container covers approximately 200-250 square feet.
Two Part Adhesives & Sealers
Mapei Ultrabond ECO 995 introduced in early 2010 is a combination adhesive and moisture protection application. Benefits with the product offer a one step application with most hardwood and bamboo floors. Project time and costs are reduced as ECO 995 can be applied with installation immediately following. No more waiting for other hardwood sealers to cure.
ECO 995 is sold in five gallon containers with costs near that of the Bostiks MVP. Recommended spread rates or amount that should be applied will vary slightly on type of hardwood being installed. A general rule of 40 to 55 square feet per gallon can be used for products less than 5/8 inch in thickness.
Another popular two part product is the Bostik Vapor Lock, described by the company as being a one part rapid tacking, moisture-cure urethane adhesive, and vapor retarding membrane. The application is similar to Mapei’s ECO 995, but does have significant differences in spread rates that depend on the hardwood thickness being used.
Both products mentioned above are not a cure all solution for excessive moisture problems or readings exceeding 15 pounds of moisture emission with concrete slabs. Consult with each manufacturer specifications for proper usage.