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The Importance Of Tile Underlayment

Tile underlayment is an important step when laying tile that is often overlooked. That step involves installing a good tile underlayment. But most people don’t even know what tile underlayment is. 

tile underlayment

To find out more about tile underlayment, let’s take a look at a few different types of tile underlayment and what they are for. Each of them serves a different purpose and all are quite valuable in today’s world. 

What Is Tile Underlayment?

What people don’t realize is that tile floors have three layers. There is the subfloor and the tile, yes, but there is also one layer in between the two called the tile underlayment. This is the most forgotten layer.

The purpose of the tile underlayment is to smooth out uneven spots in a subfloor and give something for the mortar to adhere to. Aside from that, a tile underlayment will offer water and air barriers for your floor. 

How to Tile Underlayment

Types Of Tile Underlayment

There are only a few types of tile underlayments still in circulation today. While older options are outdated, here are a few options that are unlikely to go out of style anytime soon. These underlayments are nearly timeless. 

Best Professional: Backer Board

This is the most common type of tile underlayment and the most preferred by contractors. Backer board comes in four-foot-by-eight-foot and three-foot-by-five-foot panels making it easy to lay in most areas.

More often than not, a layer of thin set is added to the subfloor then the backer board is added. After that, it is screwed down and the tile is adhered to the tile. This is one of the best ways to safely and securely install the tile. 

Most backerboard is made of cement so it can be difficult to cut through without the right power tools made for cutting. For more info on backer board, check out this tile backerboard guide. 

Best For Uneven Floors: Pourable Underlayment

Another great option is pourable tile underlayment which has many unique uses. You install it by pouring a bed of mortar to create a concrete slab to lay your tiles on. This is perfect for uneven floors.

Because you can create an even floor without even trying. All you need to do is pour the concrete on the floor and use a trowel to make sure it is smooth. Then, let it dry and use it as a sort of subfloor/ tile underlayment. 

Most tile underlayments made of concrete are one to two inches thick. But if the difference in the lowest and highest point is larger than two inches, you can pour it thicker. But if four inches are more, you will need to build a new subfloor. 

Best For DIY: Membranes

These polyethylene tile underlayments are flexible and come in rolls like carpet. They are made to add protection from water, cracking, and even help insulate your floors. They can usually be used instead of backerboard. 

This type of membrane is usually fairly easy to install and can be purchased at any hardware store and at many places online. The only thing you need to pay close attention to is taping and filling any seams. 

A membrane like this should not be installed on uneven or cracked floors. The floor will need to be smooth and level. Otherwise, you won’t have the protection that you need and the tile may crack under pressure. 

Installing Tile Underlayment

Installing Underlayment

Installing underlayment is very important and it is crucial that it is done correctly. Because the most common type of tile underlayment is backer board, that’s what we’ll use as a reference. Especially since it can be used on both walls and floors. 

Step 1: Check For Level Floor

The first thing you want to do, no matter what type of underlayment or subfloor you have, is make sure the floor is level. If you have an uneven or non-level floor, the tile floor will also be uneven, which leads to safety concerns 

For a concrete floor, use a thin-set mortar to level it. For a standard wooden floor, you can either build up for uneven floors, or you can add thinset. If you do add thin-set, then add a thin layer that is no thicker than 3 inches. 

Step 2: Fill Cracks

Next up, fill the cracks in the floor. This is important as you need it to be even and stable. For concrete floors, fill the cracks with a concrete filler. For wood cracks, fill the cracks and seams with a wood filler.

Wood filler is easy to use and anyone can use it. Sand down any bumps in the floor as well as these will cause the underlayment to have a bump or it will break the underlayment, and tile, in the process. 

Step 3: Add Thinset

Now that the floor is even and dry, it’s time to add thinset. Yes, even if you added mortar to level the floor, you need to add it to give your backerboard something to stick to. So add a thin layer to your floor.

Only add the amount you need for one piece of backerboard plus an inch or two on either end. You need to use a slow-drying thinset as well as you want to be able to adjust the backerboard after you lay it down if need be. 

Step 4: Place Backerboard

Finally, it’s time to place the backerboard. You can place it, one board, at a time while the thinset is drying. Just don’t let the thinset dry all the way before placing the backerboard down. If you have a wood floor, this is when you screw it in.

Screw it in while the thinset is wet or else you will crack it. So screw the backerboard down. Yes, even if you have wood floors, the thinset is necessary to help secure the backerboard to the subfloor correctly. 

Step 5: Add Thinset And Tile

Now that the backer board is down, you can start laying your tile. To do so, you’ll need to add yet another layer of thinset for the tile to stick to. This is different than the other type of thinset, so make sure you use the right kind.

Ask an associate or professional for help or read the label to make sure it is for the correct use. Then, you can lay the tile, grout the tile, and let it dry. For a complete guide on laying tile, check out this tile guide

Buying Tile Underlayment Online

Buying Tile Underlayment Online

You can buy any type of underlayment that you can imagine online, but there are a few problems with doing so. Backerboard has insane shipping because it is so heavy and thinset isn’t easy to transport either.

So if you do buy tile underlayment online, your best bet is to get a membrane, which is the best way to lay tile underlayment yourself if you are a beginner. It’s easy to use as long as your floor is level.

Uncoupling Membrane

This is the standard type of membrane to use for tile underlayment. It is the standard orange color, texture, and size. It works well to prevent cracks, waterproof your floor, and provide a sound place for the tile to lay.

The price is quite standard as well. One roll will cover about 300sqft of space. So this is easily one or even two rooms. While this is a bit more expensive than buying in a store, getting it online is sometimes worth it.

Cork Underlayment

Cork tile underlayment is a type of tile underlayment similar to the standard membrane. The membrane resists the transfer of stress cracks from the subfloor and can even help soundproof your room.

You can either glue this type of cork tile underlayment down or since it is thicker than other membranes, you can loose-lay it, which means it doesn’t need an adhesive. However, extra adhesion is always recommended.

Heated Floor Membrane

This uncoupling flooring mat is both durable and flexible. But that isn’t its greatest feature. What makes this one so special is that it has grooves that allow cables used in radiant floor heating to pass through.

Radiant floor heating is an amazing flooring option that allows heat to come from the floor. This type of underlayment is perfect for those types of floorings even though tile is usually not recommended for radiant floor heating. 

Which Tile Underlayment Should I Choose?

If you are hiring a professional, then trust them to choose the right tile underlayment for you. If you are experienced in laying tile but want to do it yourself, then you can choose backerboard. Just make sure the floor is level first. 

But if you are new and worried about the process, combine a leveling floor system like thinset with a membrane. This will take care of it all and is the easiest type to do. Especially if the thinset is self-leveling. 

That said, if you have the extra cash for labor, hiring a professional is the easiest way to get the job done. They can lay your subfloor, tile underlayment, and tile all. Just make sure you get an estimate before they start and you’re set.