A flawless foundation is key to every flooring installation. Whether you’re installing hardwood or LVT, the groundwork you lay is the cornerstone of durability and performance.
In this guide, we will walk you through the steps to prep a concrete subfloor with the MAPEI system. Keep reading for insights to ensure that your flooring projects are built on excellence – one that’s firmly grounded, quite literally.
What do you need to prep a concrete subfloor?
Typically, you’ll need a patch, self-leveler and primer for subfloors with known moisture issues. Additionally, you can use a moisture barrier primer to handle moisture issues, before using any patch or leveler product. Beforehand, make sure the concrete is clean and free of any debris or paint.
What’s the difference between subfloor patching compound and self-leveler?
For small areas like a hole, dip, or crack, use patch. However, do not apply patch to an entire floor! It’s intended for small areas that require only a small amount of product to bring it level with the rest of the floors. On the other hand, a self-leveler is made to cover the entire floor surface, leaving a uniform and even finish. If the slab floors demands it, there might be instances where using a patch and level becomes necessary.
How to Prep A Concrete Subfloor For a Glue Down Installation
Test For Moisture Before Applying Any Product
In order to determine which product to use, be sure you know what the moisture condition is of the slab. MAPEI recognizes a Calcium Chloride test or an In-situ probe, Relative Humidity (RH) test. Furthermore, in order to use Planipatch or Novoplan 2 Plus, you must have a good test result to stay within the guidelines. It’s important to know what products to use if moisture levels are high. Let’s get right into that topic now.
Here’s a Guide to Choosing the Right Products
Products to use in high moisture environments:
- Patches: Quickpatch or Ultraplan Extreme 2
- Self-leveler/Primer: Novoplan and Primer T
- Moisture Barrier: Planiseal PMB
- Adhesives: Ultrabond ECO 995 and Ultrabond ECO 985
Products safe to use in environments within moisture guidelines:
- Patch: Planipatch
- Self-leveler/Primer: Novoplan 2 Plus and Primer T
- Moisture Barrier: Planiseal PMB
- Adhesive: Ultrabond ECO 980
Note: this is not a complete list of MAPEI’s products, just the ones we covered in our Pro Shop Talk episode. For MAPEI’s full product lineup, see their website here.
Quickpatch and Planipatch – Patching Compounds for Isolated Areas
For slabs with moisture issues, using Quickpatch can fill in deeper holes up to to 1 1/2″. A bonus is it performs well no matter the moisture levels. However, slabs with no moisture problems, use Planipatch up to 1/2″. Accordingly, it is crucial to consistently conduct moisture testing before utilizing this product, as it is not specifically designed for areas with high moisture content.
Novoplan 2 Plus and Primer T – Self-Leveling System
Using Primer T in with Novoplan 2 Plus is a must as it aids the self-leveler to flow out and set up properly. By applying the primer, you effectively block subfloor moisture from infiltrating the self-leveler. Additionally, performing a moisture test beforehand provides valuable insights into the presence of any potential moisture-related problems. MAPEI recommends applying an added moisture barrier when levels are high and always before gluing down flooring.
Planiseal PMB – Roll-on Moisture Barrier
The best insurance against moisture damage is to apply a roll-on moisture barrier. Visually, you can easily see when you have 100% coverage and trust that your floors won’t be ruined by ground water.
Application: Use a 1/4 nap roller to roll it out thin – the thinner the better. Make sure that it looks wet and all of the subfloor is covered.
After applying this sealer, make sure it’s dry before gluing over it – no moisture testing is needed! Having applied a moisture barrier, you can use the Ultrabond ECO 980.
Incidentally, some installers choose to forego using extra products like Planiseal PMB and instead use Ultrabond ECO 995 as an all-in-one moisture barrier and adhesive. Keep reading for more details.
ECO 995 and ECO 985 – All-In-One Adhesives
Functionally, both adhesives are 2-in-1 moisture resistant Urethane adhesives. Ultrabond ECO 985 stands out as a Modified Silane (MS) and Urethane hybrid adhesive. This unique formula not only simplifies the cleanup process but also is ideal for installing prefinished flooring.
For more details on these products, see our guide here.
Glue Application Tips:
It’s crucial to note that when using these adhesives, you must adhere to the 3-step key-in method. Initially, apply or key-in the adhesive using the smooth side of the trowel. Following that, proceed to trowel the glue. Lastly, comb the adhesive perpendicular to the floors along the long edges of the boards, maintaining a 1-inch overlap with the previous glue line.
What should you do to prevent future moisture problems?
Use Planiseal PMB! Utilizing a moisture barrier is, without a doubt, the best way to prevent future problems. Even if there’s no sign of too much moisture currently, doesn’t mean there won’t be later on.
Interestingly enough, we frequently hear stories about installers receiving callbacks months or even years down the line, all related to issues of moisture impacting their wooden floors.
To avoid replacing an entire floor, here’s a couple steps to take to insure yourself:
- Read the instructions! Know the products you’re using and their moisture requirements.
- Do the appropriate moisture tests. See what type of testing is required for the product you’re using.
- Document your moisture tests in writing for every job. Consequently, this will help you know what the situation was when you initially prepped the subfloor. In case issues arise down the line, you can safeguard yourself by referring back to these documents. Furthermore, remember to capture photos and videos, complete with electronic date and time stamps, to facilitate more convenient access.
- Use a moisture barrier and/or moisture resistant materials. To effectively minimize callbacks, it’s essential to address moisture during the installation process. Select the suitable products based on the prevailing moisture conditions. Moreover, ensure to communicate to your customers the reasons behind your choices and the methods employed to protect them from potential moisture-related concerns in the future.
- Make sure the subfloor is clean, dry, flat, and sound before installing the flooring.
How could you mess up using these products?
Patches: Don’t over wet them and mix in too much water. Be sure to work quickly with Planipatch after mixing it as you only have 10-12 minutes to apply before it sets up.
Self-levelers: Again, don’t over wet the product before applying it.
Moisture barrier: Don’t apply too heavily but in a consistent thin layer. Should you come across regions where it has filled a gap, you have the option to rectify this by carefully scraping out the excess and then reapplying the material.
Adhesives: Use the correct trowel size. Avoid using just any trowel you happen to have in the van. Instead, opt for the trowel specifically recommended for each individual product. If there’s a trowel clip included, use it appropriately. This will give you 100% coverage and keep you within warranty. Remember, when using MAPEI adhesives Ultrabond ECO 985 and 995 as an all-in-one, do the three-step application!
We’re here to help you get the right products for subfloor preparation
Not sure what products you’ll need for your flooring project? Get in touch with us at one our Pro Shop locations. We have everything you need to stay on time, on budget, and on design.