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Topically Applied Slab Densifiers

Spray-on Concrete Slab Densifiers, Hardeners & Moisture Cures

Slab DensifiersThese products, commonly referred to as “slab densifiers,” are just different types of silicoid densifiers added to the concrete mix before the pour that have been on the market for over thirty years. They are finding new markets because of all the issues surrounding concrete moisture and moisture sensitive floor coverings.

Essentially they work exactly the same as the silicoids that are entrained into the concrete prior to its placement such as Barrier One and Concure. They are just “after-applied” using a low pressure sprayer. The science of these slab densifiers is such that they close the porosity, i.e. fill the capillaries, of the concrete and thereby “trap” the excess moisture not needed to hydrate the concrete and prevent it from escaping through the top of the slab. I’ve heard some people refer to these systems as “spray and pray.”

The problem with all of these slab densifiers is twofold

First, they violate ASTM-F710 in that they are applying a densifier to the concrete that cannot be removed by mechanical means. This is particularly true of the products that are added at the mix plant.

Second, they can make the surface of the concrete so dense that they are extremely difficult, at best, to bond to with current industry standard flooring adhesives.

For these reasons, the major floor covering products manufacturers have come to a disqualifying warranty position regarding the use of their branded adhesives over concrete that use slab densifiers. Essentially that position is, even if you use their branded adhesives they will not honor a bond warranty. Most of the major manufacturers have position letters available that explain this in detail. There are a few exceptions but it’s imperative that the flooring contractor understand how to deal with these situations. I have personally been through several where it comes down to an “Oh crap” moment when they find out about these exclusions after there is a problem.

The Flooring Contractor Must Be Educated About Slab Densifiers

It’s extremely important for the flooring contractor to understand what the protocol for activating the warranty from the densifier manufacturer is so that they don’t inadvertently create a situation where the end-user doesn’t have a bond warranty for the flooring. What needs to happen if you have to install over concrete with a product like this is to find out EXACTLY which product was used. Go to that manufacturers website and search for their warranty information. There will typically be a form that has to be filled out by the flooring contractor and signed by the additive or densifier manufacturer BEFORE anything gets installed. The process usually always involves doing bond tests with all adhesives, patches, primers, flooring materials – basically anything that you’re going to bond to this concrete with topically applied slab densifiers. It is the responsibility of the densifier manufacturer to determine, based on the results, which products they will accept for the warranty. If this protocol is not followed, then the flooring contractor is assuming any and all liability for any bond failures that occur.

I’ve been through this process many many times with variable results. I’ve seen really good success and I’ve seen really bad failure. I’ve seen one densifier manufacturer’s product take six sets of bond tests with different adhesives and finally the contractor walked and told the General Contractor they didn’t want to do the job due to concerns they couldn’t bond to the substrate. I’ve seen another job that had a severe moisture issue, the densifier was applied, bond tests worked well, the flooring was applied and five years later it still looks perfect.

Much like anything else in life, if done correctly, the product works. If you get someone playing “field chemistry” it’s at best a crap shoot and you can be a big, big loser. This issue is a real hot bed of controversy right now so just be cautious if you have to install over these systems. Take some time and educate yourself to the issues surrounding their use and make sure you’re protecting yourself from liability the best that you can.

Learn More About Slab Densifiers On TFP Forums

You will find flooring professionals with experience with slab densifiers here at The Floor Pro Community. There are discussions about specific products, including this one. If you don’t find the information you need, start a new topic and ask. If you have additional information that will help an existing topic, post a reply (only members can post, but registration is free).


Chuck Milledge

Chuck started in the floor covering industry in 1995, working in the warehouse and worked his way up to Commercial Sales Manager for Kaough Distributing Co. Chuck has always believed, if you want to understand floor covering, ask a flooring installer. He spent the first 4-5 years of his career loaning himself out to installers and doing a lot of listening. Chuck continues to listen, but he also enjoys sharing that knowledge with other pros and the consumer & DIY members of The Floor Pro Community.


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