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How Proper Surface Prep Prevents Overlay & Coating Disasters

How Proper Surface Prep Prevents Overlay & Coating Disasters

3rd Apr 2024

When placing a cement-based overlay or resinous coating system, both involve similar steps to have a successful installation. They both require protecting the surrounding area, material mixing, and preparing the substrate. With these, the most complex task will be preparing the surface.

Preparing the surface to accept a flooring system is a step in every project. If the surface prep method does not produce the recommended surface profile or is even just rushed, the possibilities of bond failure increase dramatically.

When the installer has a bonding issue, the first thing the material manufacturer will look at is how well the surface has been prepared and that it meets what they recommend. If it does not, they will blame you for the issue. First, you need to follow the recommended surface prep method to obtain the correct surface profile. No one ever makes more money when the only choice is to start over.

The "What Lies Beneath" Problem

No two concrete substrates are the same. Before the surface preparation step starts, you must assess what you will be working on. Having cracks, spalls, and stains becomes a constant battle. Seldom you will find a concrete floor that will not have a defect.

Moisture vapor transmission (MVT) is a phenomenon when moisture vapor moves through the slab. Granted, concrete is like a sponge. It takes in moisture and releases it regularly. A small amount of moisture movement in and out is normal. When there is an elevated level of moisture present, there can be a problem. The material manufacturer will provide MVT limits the selected system will tolerate.

During the application of the material, if there is an elevated level of moisture vapor moving out of the slab, it will cause blow holes in an uncured coating or primer. If the material is heavy and thick, the vapor will trap at the bond line and develop a void where there will be no bond obtained. This void will be an issue in the future.

Selecting a primer or system that can manage the level of MVT will be the only option. The finished appearance of the installed system with a moisture-tolerant primer will appear to be normal but now the MVT will be in check.

Having the proper repair material for the defect type is crucial. You can repair fine cracks and small chips with neat (no added aggregate) DiamaPro® Diama-Grout, a low-viscosity, urethane resin. This material is very thin to promote great absorption and fast setting for minimal downtime. Medium size spalls, up to 6” in diameter and 2” in depth, can be filled with DiamaPro® Diama-Grout mixed with oven-dried sand or pea gravel. The sand and pea gravel need to be completely dry, and free of all water. You can buy this along with the Diama-Grout at Niagara Machine.

Most concrete slabs will have control joints or saw cuts. When concrete cures, it will shrink. Control joints are weak planes to direct the cracking within the joint and should be filled. DiamaPro® Diama-Jointis a polyurea joint filler. It sets fast to minimize downtime. It not only fills the joint, but it also fills it with a material that will aid in transferring wheel loads over the joint. This helps minimize wheel impact on the joint shoulders. Without addressing these joints or defects before installing the system, they will reflect through the cured film leaving an unacceptable appearance.

It is More Than Smoothness: Prep for Your Specific Finish

Material manufacturers will always have surface profile recommendations listed in their technical data. It is highly recommended to always follow what they say. If you have an issue, surface prep is the installer’s responsibility. This should not be rushed or dismissed.

There are flooring systems that will require a smooth, prepared surface. These systems are typically very thin, less than 10-mils. There is not enough material applied to smooth out a rough profile providing a nice-looking floor.

The primer or first coat of a thin system will be low in viscosity with an elevated level of absorption. The required surface prep will be to mechanically clean the surface with a concrete grinderwith the proper diamondtooling. The profiled surface will be free from all bond-inhibiting materials with a light texture. Niagara Machine carries grinders and tooling options to choose from that will provide the correct surface profile.

Rough surface profiles are for thicker systems. Whether resinous or cement-based, they both recommend a “tooth” to grab onto. This will take a method to produce a Concrete Surface Profile (CSP) of 3-7. A heavy shot blast or a grinder fitted with bush hammers will get you to where you need to be.

Mistakes That Make More Work Later

Before bidding on a flooring project, obtain, and read the system's technical data. When there is an issue on the job, the manufacturer will always refer to the technical data. If the installer misses a step, all material warranties are invalid. Clients will also obtain the technical information before the project starts. It is amazing how accessible this information is to the public. They too will have the knowledge available to ask pertinent questions.

If the installation instructions say a shot blast is their recommended surface preparation method, make sure you have a shot blaster available to use. They are available through Niagara Machinebut are pricey if you will not be using it again. Sunbelt Rentals, Niagara Machine’srental partner, has them available to rent in a multitude of sizes.

When using a grinder to prep the surface, selecting the correct diamond tooling will make or break the project. Time is money. By using the incorrect tool based on the grinder, the profile needed, and the hardness of the concrete, will increase the amount of time to perform the work. Niagara Machine has the tooling you will need to perform at the highest production level. They will guide you through the process of evaluating the equipment and match that with the profile needed while matching that to the hardness of the concrete floor. This process will allow you to perform the surface prep needed most efficiently.

Prep Pays Off: Happy Client and Your Reputation

Your client base and reputation are all you have when it comes to future work. If your client is happy with the work you have performed, they could provide you with potential new business opportunities. Leaving every project in a positive light is important when being a business owner.

Surface prep is only one part of any flooring project. There are multiple parts making a whole. Starting with a well-prepared surface will provide the proper base to build. During the selling phase of the project, be sure to explain to the client how you will be preparing the surface and how the method has an impact on the long-term performance of the system.

Remember, knowing the moisture level is part of the surface prep step. Purchase a Tremex surface moisture meter and perform the test with your client if possible. Explain what you are doing, how it works, and the negative impact moisture can have on the system. This could set you apart from the next person they call.


Surface prep involves much more than using a broom to sweep the floor. Mechanically preparing the surface to accept a flooring system is an especially crucial step of the installation. Figuring out what the manufacturer requires, what equipment to use on the slab, and if any potential issues could rear their head (moisture) are all parts of the entire process.

During the floor evaluation process is the time to educate your client. The more they understand, the more comfortable they will be. Granted, some clients will not care how you get to the finish line, they just want a quality job.

For all your surface preparation needs, Niagara Machine will have exactly what you need. They specialize in grinders, tooling, shot blasters, and concrete hardness measuring devices. They can get you on the right track with only one phone call.