Damp Slab and Wood flooring - Mitigating Moisture


Denise Troiano

 August 28, 2018. 10:40 PM

With my 23 years of experience in the construction industry, I have seen what high moisture issues can do to any flooring, especially hardwood floors. As a Northern transplant to South Florida, I feel confident installing hardwood flooring in my home and still want the memory of a roaring fireplace and soft wood floor underfoot. However, being in a warm, humid climate comes with some challenges when installing wood flooring. With heavy rainy seasons and slabs on grade with no basements, wood flooring can be tricky. Having lived down here for a while, I have seen more failures due to moisture than ever before.  The results include buckling of the floor, cupping, and crowning.

Before you develop a plan of attack, you should always try to find out where the moisture is coming from. The best place to start is outside. A large number of failures could be avoided with proper landscaping. A few ways to mitigate moisture penetration is to ensure that water flows away from the structure and that sprinklers are facing away from the building - these two small changes will prevent water from collecting in puddles or pools close to the slab. This excess water usually concentrates at one entry point. Some symptoms of this water infiltration include:

1. Moldy tack strips along outer walls
2. Vinyl flooring peeling easily around outer edges
3. Staining on the concrete or efflorescence

Wait a minute! I haven’t even started yet and I have to do all this work? Yes, you do if you want a durable, long-lasting floor. On average, a customer will spend between $7,000 - $20,000 on their installation. The old adage of measure twice and cut once applies here as well.

Wood is moisture sensitive and it’s critical to alleviate any potential failures. Special moisture reducing membranes can be used to block excessive moisture in the slab to ensure a durable installation.  MAPEI’s Planiseal® PMB is a one-component moisture vapor emission protection for wood and bamboo with no moisture limits. Planiseal PMB is rolled on in a thin coat, then 2-3 hours later, or when dry to the touch, is ready for the wood installation. A urethane-based adhesive must be used to install your wood floor.

One-step adhesives for moisture control is an alternative to a two-component system. Ultrabond® ECO 995 and Ultrabond ECO 985 both offer complete moisture protection. However, Ultrabond ECO 985 is a very tenacious, polymer, hybrid-based adhesive with lower VOC’s than the traditional wood adhesive.

As tricky as these installations can be, we recommend that you read the technical data sheet to fully comply with the proper installation method. As always, please refer to the NWFA (National Wood Flooring Associaton) installation guidelines.

We are always here to help with your flooring installation. Just call our Product Support Line at (800) 992-6273 with any questions.

By Denise Hibson and Product Support Team


Denise Troiano

Denise Troiano

Denise Troiano brings 24 years of experience in the tile, stone and installation products industry to MAPEI. Working with manufacturers, retailers, designers and installers during this span allows her to answer a wide range of questions from homeowners and industry professionals.


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