Install Backer Board Before Laying Tile

My wife and I were remodeling our kitchen and decided to tear the old vinyl floor out and replace it with ceramic tile. Before laying tile, we had to install backer board over the subfloor. Read on to find out how we installed some Hardiebacker board in preparation for our tiling project.

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The following instructions are how we executed this procedure. How-To Matthew always recommends following the manufacturer's instructions when possible.

Why Install the Backer Board?
When installing ceramic tile any type of floor except concrete, it is recommended that you first install some sort of backer board, whether that back board be cement, Hardiebacker, or Durock, you need an additional layer to keep the floor rigid enough to support the tile. The backer board will also protect the underlying floor joists from moisture.

We decided on using Hardiebacker board purchased from our local Lowes. It comes in 3'x5' sheets with a fastening grid stamped on one side. Ee purchased enough to cover 300 sq. ft. (about 8% more than we needed).

Procedure
1. Mix Some Thin Set Mortar to peanut butter consistency. Use latex or acrylic thinset mortar.
2. Using a Trowel With 1/4" Notches, spread the thinset mortar on the subfloor. The "valleys" of mortar created by the notches should have just a thin coat of mortar covering the subfloor. Using the notched trowel will ensure a flat and even application of mortar.
3. Position the Hardiebacker Board on the Bed of Mortar. Make sure there is an even bed of mortar underneath the board. Leave a 1/8" gap between boards (you can use tile spacers for this).4. Screw the Board Down while the mortar is still wet. With the Hardiebacker board's stamped screw pattern, knowing where to fasten the board was quick and easy. If your board does not have a pre-stamped fastening guide, put screws or nails evenly spaced about 6"-8" apart. One full sheet of 3'x5' board takes 54 screws.

A Note on Screws: HD self-drilling corrosion-resistant ribbed waferhead screws are recommended due to their self counter-sinking head that ensures a flush install. I found regular 2" coarse thread drywall screws, which can be purchased much cheaper in bulk, worked just fine as long as you made sure the head of the screw was flush with the backerboard. In high moisture applications (i.e. showers) I would use the recommended fasteners for their added corrosion resistance.

Make sure the seams of the boards do not line up with each other, in other words, do not make a simple grid where four corners meet. Offset the pattern to where only two corners ever meet.

6. Fill Any Low Spots in the floor or if the floor is slightly out of level, you can use a bit extra mortar to even the surface out. You want as flat of a surface as possible, especially if you are laying large tile!
7. Tape and Mortar the Seams with 2" wide high-strength alkali-resistant glass fiber tape.

Summary

1. Apply a bed of mortar.
   
2. Position the backer board over the mortar and screw or nail in place.
3. After the entire floor is covered, tape and mortar the joints.
   

Additional Tips
To cut the backer board, use a carbide tipped knife to score the board. With the board well scored, snap it along the score.

Traditional cement board can contain asbestos and even the newer types of backer board that do not contain asbestos are still dangerous if you inhale dust particles. This is why you should cut the boards outside if possible and avoid using any cutting method that creates dust, like sawing.

If you have to cut a lot of board, you can use a carbide blade in a circular saw but be sure to wear proper eye, ear, and respiratory protection!

If you have never tiled before, working with the backer board and mortar is good practice for the upcoming job!

Conclusion
Here is our kitchen and breakfast nook before and after the Hardiebacker board was installed. At this point they were ready for the tile!

Next: How to Install Ceramic Tile

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Relevant Sites
Here is an external link to a site with information relevant to this article.

Hardieback Website

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