How to Use Cement Backer Board

Cement backer board is an important building material for any tile installation. Properly installing and using cement backer board ensures that your tile will last for years to come. In this comprehensive guide, we will cover everything you need to know about working with cement backer boards for a successful tiling project.

Selecting the Right Cement Backer Board

There are a few things to consider when selecting cement backer board:


Cement backer boards come in different thicknesses, typically 1⁄4” or 1⁄2”. Thinner backer boards are suitable for walls and vertical surfaces. Go with a thicker 1⁄2” backer board for floor installations. The added thickness provides better support and prevents flexing.


Standard cement backer board sheets are 2′ x 5′ or 3′ x 5′ to make them easier to handle. Opt for larger sheet sizes to minimize seams if you are tiling a large area.


Look for cement backer boards that are designed for wet areas. These boards will be coated or treated to make them waterproof and able to withstand moisture. Waterproof cement board is required for shower walls and floors.


Popular cement backer board brands include HardieBacker, Durock, PermaBase, and WonderBoard. Any major brand of cement backer board will offer similar performance.

Tools Needed for Cutting and Installing

To work with cement backer board, you will need the following tools:

  • Utility knife – Use a sharp blade for scoring and snapping board.
  • Circular saw or jigsaw (with dust collection) – For straight cuts.
  • Carbide-tipped scoring tool – Optional for deep scoring.
  • Dust mask and safety glasses – Cement board dust is fine.
  • Tape measure and straight edge.
  • Caulk/adhesive for seams.
  • Screws – 1-1/4” corrosion resistant screws.
  • Washers – Use with screws to reduce risk of popping.
  • Drill for driving screws.

How to Cut Cement Backer Board

Cement backer board can be cut using basic tools for a clean edge:

Score and Snap

Mark cut lines with a utility knife or scoring tool. Use a straight edge for straight cuts. Score 2-3 passes over cut marks. Snap board upwards along score line. Scored side should face inward.

Circular Saw

For long straight cuts, use a circular saw with a dust collection system. Cut with the good face down. Go slowly to avoid cracking.


A jigsaw with a carbide grit blade can be used for curved cuts. Cut with the good face up.

Hole Cuts

For outlet cutouts, drill a hole at corners and use a jigsaw to connect. Or use a roto-zip type cutting tool.

Tip: Make cuts prior to installation whenever possible for cleaner edge. wear safety gear when cutting cement board.

Applying Cement Board to Walls

Cement backer board for walls should be installed over a code-approved moisture barrier. Here is the process:

Step 1: Install Moisture Barrier

Cover studs with 15lb asphalt-impregnated felt paper or a 4mil polyethylene moisture barrier. Overlap seams 6-12 inches.

Step 2: Mark Stud Locations

Mark stud centers on the moisture barrier so you can attach cement board at proper points.

Step 3: Apply Adhesive

Run a serpentine bead of tile adhesive or construction adhesive along studs. Use enough to create a strong bond.

Step 4: Attach Board

Screw boards vertically to studs using 1-1/4” backer board screws spaced 8” apart across studs and 1” from edges and seams. Avoid over-driving screws.

Step 5: Tape Seams

Fill all seams and gaps with tile adhesive. Then embed alkali-resistant fiberglass mesh tape into adhesive.

Allow adhesive at seams to fully cure before tiling. Wet area boards may not require seam taping if using waterproofing membranes.

Applying Cement Board to Floors

Here are the key steps for installing cement backer board over plywood subfloors:

Step 1: Install Underlayment

Screw 1/4″ or 1/2″ plywood or OSB underlayment over joists to strengthen the subfloor.

Step 2: Mark Studs

Mark joist locations on the underlayment to identify screw points. Having a strong underlayment is important.

Step 3: Apply Adhesive

Run a serpentine bead of construction adhesive on the underlayment where boards will be placed.

Step 4: Fasten Boards

Screw boards to subfloor with 1-1/4” backer board screws spaced 8” apart across joists and 1” from seams and edges. Offsets seams from layer below.

Step 5: Fill Seams

Fill gaps with tile adhesive and embed alkali-resistant mesh tape. Allow to fully cure before tiling.

Tips: Going with a thicker 3/4″ plywood underlayment provides a stronger base. For large floors, use uncoupling membranes over the cement board.

Waterproofing Cement Board

Any cement backer board used for wet areas like showers needs to be waterproofed:


Apply a waterproofing membrane designed for bathrooms per manufacturer instructions. RedGard, AquaDefense, and Kerdi are popular options.

Caulk Seams

Use silicone or urethane caulk to seal all seams, corners, and fastener points. This creates a water-tight seal.

Extend Below Tile

Waterproofing should extend 2-3 inches below the lowest point where tile will be installed.

Allow to Cure

Let waterproofing materials fully cure for 24-48 hours before applying tile. This prevents issues with moisture.

Waterproofing is a critical step. Improper waterproofing leads to mold, wall damage, and loosening of tiles over time.

Prep and Priming Cement Board for Tile

Once installed, properly prepare cement backer boards prior to tiling:

Clean Surface

Wipe the surface free of any dust, dirt or debris that could impact bonding.

Seal Exposed Board

Paint any exposed cement board edges with a drywall primer to reduce moisture absorption.

Skim Coat Screws

Cover all fastener indentations and seams with a skim coat of mortar to level out.

Prime Entire Surface

Apply a tile primer across the entire surface following label directions to improve adhesion.

Priming ensures a strong bond between your thinset mortar and the cement backer board.

How to Tile Over Cement Backer Board

You are now ready to start tiling. Follow these best practices:

Choose Appropriate Mortar

Use a polymer-modified thinset mortar suitable for cement board and your tile type. Budget enameled ceramic tile may require a high quality mortar.

Check Tile Backs

Examine tile backs for any dust, loose grains, or contaminants that could weaken bonding. Clean as needed.

Apply Mortar

Use a notched trowel to spread a thin layer of thinset mortar across the area, using the appropriate trowel size. Apply only enough that remains sticky before adding tile.

Work in Sections

Tile a small section at a time so the mortar doesn’t dry out. Periodically remove and check mortar contact of already laid tile.

Use Tile Spacers

Place tile spacers between tiles for consistent grout lines. Remove once tile is set before grouting.

Grout When Ready

Let mortar cure fully per product directions before grouting. Typically 24-48 hours. Use polymer-modified grout for best results.

With the right prep and materials, your tile installation over cement backer board will last for decades.

Tips for Working with Cement Backer Board

Keep these tips in mind when using cement backer boards:

  • Acclimate boards to room temperature before installing to prevent cracking as they warm up.
  • Wear safety gear – cement board dust contains silica. A mask is important.
  • Stack flat prior to use. Do not leave boards exposed to moisture or they can weaken.
  • Handle with care once cut. Edges can be sharp and boards can crack if roughly handled.
  • Use in dry areas only unless the backer board is specifically designed for wet rooms.
  • Ensure adequate ventilation when working in enclosed spaces to reduce dust.

Advantages of Cement Backer Board

Cement backer board has become the preferred substrate for tile compared to drywall. Here’s why it’s beneficial:

  • Provides a strong and rigid surface that resists movement or flexing.
  • Offers superior bonding surface for mortar and tile.
  • Won’t break down or deteriorate due to prolonged moisture exposure.
  • Resists mold growth.
  • Fire and impact resistant.
  • Thinner than mortar beds for thinner assemblies.
  • Works for both wall and floor applications.

For tiling projects both large and small, cement backer board is worth the small additional cost over drywall.


Here are answers to some frequently asked questions about working with cement backer board:

Can I use drywall instead of cement board?

Drywall is not recommended as a tile backer board. It lacks the strength and moisture resistance of cement board.

How thick should cement board be for flooring?

Use 1/2″ cement backer board for floors and ceilings. The added thickness prevents flexing underfoot.

Does cement board need to be sealed?

Exposed cement board edges should be sealed with primer. But there is no need to seal the entire surface prior to tiling.

Can cement board get wet?

Standard cement board can get wet temporarily but should not be used in prolonged wet environments. Use waterproof cement board for showers or exteriors.

How do you prepare cement board for tile?

Fill screw holes, skim coat seams, prime, and ensure the surface is clean. This provides the optimal bonding surface for thinset mortar.

What thinset is best for cement board?

Use a polymer-modified thinset mortar designed for use with cement backer boards per manufacturer specifications.

Can you attach tile directly to cement board?

It is not recommended. A layer of thinset mortar should be used between the tile and cement board to provide adhesion.

How do you cut cement board without dust?

Use a circular saw or jigsaw with a dust collection system. Also wear a safety mask to contain dust.


Installing tile over a cement backer board provides a permanent, water-resistant tiling surface. With the right preparation and installation process, cement backer board offers a strong, stable base for beautiful tile work in any room. Just be sure to take safety precautions when handling and cutting cement board. The extra effort is well worth it for many years of durable, crack-free tile finishes.