Common Mistakes with Concrete Substrates

In this article, I will simplify four common mistakes with preparation for concrete substrates that can lead to flooring failures. This article won’t address not testing for moisture as it could encompass its own article and soap box rant by me.

Not Clean Enough

This category needed to be number one as the greatest number issues and failures happen here. Just because it looks clean doesn’t mean it actually is. Every mitigation, adhesive, and glue-down flooring manufacturer will reference NWFA Guidelines and/or ASTM test methods for how clean your concrete needs to be.  There may be a greater requirement specified by the manufacturers. While the surface profile and absorbency may vary depending on product being used, ALL manufacturers require the substrate to be clean and free of bond breakers. Become educated on how to determine if there are contaminates/bond breakers on your substrate. Reach out to technical departments, manufacturer reps, and attend trainings focusing on concrete prep.

Not Flat Enough

We should all be familiar with the NWFA flatness standards for a concrete slab being 3/16” in 10’. This is a minimum standard that “may” be good enough, but with some installations, it may also not be. Keep in mind that what you can get away with on a nail down over plywood installation is quite different than a direct glue down on concrete, which is why the flatness standard is even looser (¼” in 10’) for this application. And a floating installation should be even flatter. Very few slabs are flat enough to not require any additional prep. Knowing how to measure for flatness is obviously important. A 10 foot piece of straight material works at a minimum (provided it is actually straight). You can also use lasers, string line, and a story pole, or gas levels. There are also systems that will give you digital results direct to your phone and even software that will give you 3D modeling of your subfloor. Again, if you are not familiar with how to determine your flatness, get to a training. The NWFA, and many manufacturers offer training on how to measure and address flatness of a subfloor. What you will learn will make you look more professional and help reduce your failures. With today’s very educated and demanding consumers, “good enough” is less and less good enough to keep you out of trouble.

Not Paid Enough

One of our industry greats, Lon Musolf, used to say, “If you don’t have time to do it right the first time, when will you have time to do it again?” I will parallel his statement and say, “If you aren’t getting paid enough to do it right the first time, who is going to pay you to fix your mistake?” The simple fact that you’re reading this article says you’re a step ahead of the contractor who doesn’t. The fact that you invest your time and resources into attending NWFA and manufacturer training places you ahead of the contractor who does nothing. If you are worth more, then charge more. Period. And NEVER, NEVER, be afraid to charge appropriately for doing it the right way the first time. Being educated will make you more confident in discussing what is necessary for success.

Not using the right equipment

Whether it is a new pour or existing, every concrete slab is different. The equipment needed to prepare each slab  to meet the industry standard or manufacturer specific requirements, can also vary dramatically. Whether you need to prepare the slab for moisture mitigation or for a direct install will also determine what will be necessary to properly prepare the slab and what piece of equipment will be needed.  These different requirements are related to concrete surface profile (CSP) and absorbency.

Here’s one example of a common mistake that many flooring contractors make:

“We ran the diamond grinder across the entire floor.”

That’s great and better than most, but, even if it is clean enough, does it need to also be “absorbent”? Some mitigation systems and adhesives require a more-absorbent substrate. These slabs may require shot blasting and the use of other specialized equipment. So, in this case, all of your efforts still set you up for failure. Just because one particular piece of equipment works “most” of the time does not mean it will work “all” of the time.

You are going to be held accountable for these requirements, so don’t get surprised by them. Get educated and be better today than yesterday.

Don Jewell is the head of technical for Loba-Wakol LLC in Wadesboro, North Carolina. He can be reached at don.jewell@loba-wakol.com.