On top of that, cement board also reduces the chance of rot in theunderlying wall studsor floor joists.

Because cement backer board is porous,thinset, grout, and mortar adhere well to it.

What Is Cement Backer Board?

Cement backer board on wooden floor with light and shadows casted across

The Spruce / Margot Cavin

For years, interior walls were finished with wood strips (lath) laid over wall studs.

Plasterers then troweled on plaster and waited weeks for it to fully dry.

Think ofcement backer boardas a tile-appropriate equivalent of wallboard.

Cement backer boards stacked closeup

The Spruce / Margot Cavin

Once this happens, the studs can begin to dampen.

Mold, mildew, and rot result.

In short, tile and grout are not inherently waterproof.

Cement backer boards screwed into plywood floor by hand

The Spruce / Margot Cavin

Wood is not an acceptable material to use for places with constant water usage such asshowersand bathtubs.

Regular drywall is not appropriate either.

Many professional installers even recommend against usingwater- or mold-resistant drywallin high-moisture areas.

Cement backer board is mainly used as a sub-surface for tiling.

Note that control joints should still be used.

Crack isolation membrane does not eliminate the need for joints.

Manufactured veneer stoneis another use for cement backer board.

Not only that but drywall is not a strong enough material to support veneer stone’s considerable weight.

The paper facing will simply tear away.

Tip

Cut with a utility knife whenever possible, as this nearly eliminates dust.

Apply the Mortar

Applythin-set mortaron the underlying surface and comb it out with your trowel.

Keep the cement backer boards about 1/4-inch apart.

Position the Board

Press the board into the mortar and hold it firmly for a moment.

Re-apply mortar to either the board or the surface, as necessary.

Just as you would with drywall, double-check the screw heads are slightly depressed below thecement backer board surface.

Finish the Installation

Cover and mortar the seams with fiberglass seam tape.

Major Brands of Cement Backer Board