USG Durock is undeniably one of the best cement boards in the market. It’s durable, strong, and highly resistant to crumbling.
When installing Durock, it’s important to adhere to the manufacturer’s instructions. For instance, most people don’t know that USG recommends Durock be installed using thinset.
In today’s article, I will discuss the best thinset for Durock cement board and a few more things you may be interested in.
What is the Best Thinset for Durock?
According to USG, the best thinset for Durock is a latex-fortified mortar. Unlike regular mortar, latex-fortified mortar has superior features.
From this type of mortar, you are guaranteed a stronger adhesion between Durock and the substrate which will last for decades.
Latex-fortified mortar is also highly resistant to moisture, heat, and other elements. The other thing that I like about using latex-fortified mortar is that it’s ideal for Durock which will be installed in exterior applications.
You’re probably wondering why USG recommends latex-fortified mortar yet there are plenty of other options out there.
First of all, this type of mortar has an advanced bonding strength. When used on Durock, it ensures longevity. Also, it’s more compatible with the Durock cement board.
If you plan on installing Durock cement board anytime soon, I would advise you to adhere to USG’s recommendation and use a latex-fortified mortar as your thinset.
Going against these instructions can lead to cement board failure and it could also void your warranty.
Does Durock Need Thinset?
Before we go much deeper, let’s circle back to the beginning. Does Durock need a thinset? Surprisingly, a lot of people do not use thinset when installing Durock and other cement boards.
Most people assume that screwing cement board is enough to bond it to the floor or wall. However, cement board manufacturers like USG have a different opinion.
Durock needs thinset for various reasons, which include;
• To create a strong bond between it and the substrate. As mentioned earlier, screwing cement board to a substrate is never enough. A layer of latex-fortified thinset goes a long way in ensuring the bond between Durock and the substrate is super strong.
• The other reason why Durock needs a thinset is for waterproofing purposes. If you’re installing Durock in a bathroom or any high-moisture room, thinset closes any seams that may let water pass through. Therefore, if you’re interested in creating a watertight setup, you must some thinset on Durock.
• Thinset creates sufficient support for the Durock cement board. With thinset below the Durock, you will be assured of sufficient stability and firmness.
• Finally, thinset can be used to repair or patch up damaged Durock. Though durable, Durock is sometimes susceptible to cracking or minor damage. But if you have some thinset by your side, all you have to do is patch it up and it will look as good as new.
Can You Use Unmodified Thinset with Durock?
Yes, you can. But I wouldn’t recommend it. Unlike the latex-fortified thinset USG recommends for Durock, an unmodified thinset doesn’t offer a stronger adhesion between Durock and its substrate.
The biggest difference between these two types of thinset is that the latex-fortified is filled with additives that offer better adhesion and additional features like waterproofing.
The only advantage of using an unmodified thinset with Durock is that it’s cheaper. So, if you are on a budget, you may gravitate toward this option. But considering the weak adhesive strength, is it worth it?
How to Install Thinset Below Durock?
Now that you know which type of thinset you should use with Durock and the reasons why it’s the ideal choice, allow me to take you through the installation process. It’s pretty straightforward and you don’t need any special skills.
Step 1: Clean up the subfloor
Just because Durock is strong doesn’t mean that you should install it on a surface without preparation. Cleaning up the subfloor ensures a flawless installation of the Durock cement board.
Start by sweeping any debris or dirt. Part of the cleaning process also entails repairing the subfloor if it is damaged.
Step 2: Prepare the thinset
For the Durock cement board, you’ll be using a latex-fortified thinset. Buy some from your brand of choice and prepare it according to the manufacturer’s instructions.
The good news is that most fortified mortars are sold in premixed bags. Therefore, you don’t have to go through the messy preparation process.
However, if the thinset is not yet mixed, find a bucket of water and mix it as per the provided measurements.
Step 3: Apply the thinset to the subfloor
Using a quarter-inch square notched trowel, start spreading the thinset over the subfloor. Ensure you cover the entire area that you plan to install Durock, making sure you create a consistent layer.
Step 4: Place the Durock over the thinset
Grab a piece of Durock and push it gently over the thinset. Press it so that it bonds firmly with the thinset. You can check and correct the evenness.
Step 5: Finish up by nailing screws into the cement board
Thinset and screws work together to secure Durock into a substrate. Never rely on only one of them.
Drive screws into the Durock cement board, ensuring they’re 8 inches apart, and let the thinset cure before exposing the Durock to traffic. Make sure that you use specialized cement board screws.
Later on, you can use the latex-fortified thinset to cover taped joints on the seams of Durock panels. Here you’ll have to use a drywall knife instead of the trowel.
Can You Use Mastic with Durock?
Sure, you can. USG allows contractors and DIY builders to use mastic to adhere Durock cement board to walls or floors. Mastic should be applied to the smooth side of Durock to get a stronger bond.
But before you use mastic, confirm that it’s compatible with the subfloor. This will help you avoid adhesion issues in the future.
Compatibility is a key deciding factor when choosing what type of thinset should be used with Durock and the substrate below.
Tips for Choosing the Right Thinset for Durock
As we’ve seen in this article, not all thinset mortars are suitable for Durock. Even though I have already recommended the best type of thinset for Durock, here are some tips that will point you to the right option;
• Confirm straight from the manufacturer. All cement board manufacturers have a specific recommendation of the best thinset for their cement boards. This should be the first thing to check.
• Go for modified or fortified thinset mortars. Fortified and modified are terms that are used interchangeably to refer to mortars. And this type of thinset has a superior adhesive strength which guarantees lasting results.
• Choose a thinset mortar that is compatible with cementitious products. Durock is a cement board therefore it will only be compatible with cementitious mortars.
• Consider a thinset with waterproofing capabilities. If you’ll be installing the Durock in a bathroom or kitchen, choose a thinset mortar that is waterproof.
• Never forget to check the setting time of a thinset mortar. If you’re in a hurry to install Durock, consider thinset which has a quick setting time. But if you’re a newbie to such a project, go for a thinset with a longer drying time as it’ll give you more room to correct errors.
Are There Alternative Options to Thinset for Durock?
Thinset isn’t the only product you can use to adhere Durock to a subfloor. There are plenty of other alternatives like construction or epoxy adhesives.
These alternatives have a much higher bonding strength. But the only problem is that they are super expensive, especially if you’re installing Durock in a large area.
If you decide to use an adhesive instead of thinset, Durock has its flooring adhesive known as Brand Genius. It will stick Durock to concrete, wood, metal, and a wide range of subfloors.