Gypsum and Cement Backerboards

This story shows how to work with gypsum and cementious backerboard.

Intro

Backerboard products have made tile installation a more accessible project for the do-it-yourselfer. In the world before backerboard, the first step in a tile job was installing a mortar bed to provide structural rigidity so that the installed tiles couldn't flex and crack. Laying a smooth bed required the skilled touch of an experienced craftsman.

But just as drywall panels have made wall and ceiling installation less demanding than plastering, backerboard makes tile prep a job that doesn't require an apprenticeship.

Consult with several tile suppliers for recommendations on the best backerboard for your project. But be aware that the dealer's inventory may color the advice. For example, a supplier who stocks only cementious backerboard probably won't recommend gypsum panels, even though they are easier to cut.

Checklist

Time
Approximately 20 minutes per panel

Tools
Tape measure, drywall T-square, rasp, mixer, margin trowel, notched trowel for floor application, utility knife and standard hole saw to cut gypsum panels, carbide scriber or abrasive wheel and carbide-tip hole saw to cut cementious panels

Skills
Measuring, marking, cutting, driving screws

Prep
Gather tools and materials at job site.

Materials
Backerboard, corrosion-resistant screws, compatible fiberglass mesh tape

Gypsum Backerboard: Step 1

Gypsum backerboard is easy to cut and shape. For straight cuts, you simply use a sharp utility knife to score, snap, and cut just as you do with gypsum wallboard. A jab saw makes internal cutouts.

Gypsum Backerboard: Step 2

Be aware that the board has a face side a different color from the back. Follow the manufacturer's directions for adhering the board in a thinset bed. Backerboard requires special screws, so don't substitute ordinary drywall fasteners. Follow the fastener spacing recommended by the manufacturer.

Cementious Backerboard: Step 1

When you're working with cementious backerboard, use a carbide scriber for the initial scoring. Make several passes with firm pressure.

Cementious Backerboard: Step 2

After you snap the board, keep the cut open at an angle while you slice with your utility knife. It will probably take several passes to separate the pieces. Smooth the cut edges with a rasp.

Cutting Small Holes: Step 1

Set the board against the pipe or other obstruction. Mark the diameter of the hole to be cut. Use a tape measure to locate the center of the hole. For faucets, measure the location of each faucet hole from the wall and from the tub or floor.

Cutting Small Holes: Step 2

Use a cordless drill and carbide-tip hole saw or coring saw to cut small holes in backerboard. Place the drill point of the saw on the mark you made, and use light pressure and high speed to cut through the backerboard.

Cutting Large Holes: Step 1

When the diameter of a hole to be cut exceeds the size of available hole saws, measure the obstruction and use a compass to mark its location on the backerboard. Then score completely through the backerboard mesh with a utility knife or carbide scriber.

Cutting Large Holes: Step 2

Support the cutout with the palm of one hand, if necessary, and tap the scored edge with a hammer. Continue tapping until the surface around the circumference crumbles. Alternatively, drill a series of small holes around the circumference.

Cutting Large Holes: Step 3

Using a utility knife, cut through the mesh on the opposite side of the board. Push the cutout through and smooth the edges with a rasp, serrated contour plane, or masonry stone.


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