Durock cement board is the lightest (by weight) backerboard product available on the market. It can be installed by determined do-it-yourselfers rather than hiring a professional. This material is most commonly used on floors and walls in preparation for a tile application; the cement board is water resistant and strong enough to support the heavy weight of even natural stone tiles. This board requires only adhesive and nails, as well as some care and attention from the installer, to create a stable support surface for your tiles.
Things You'll Need
- Mineral spirits
- Thinset mortar with latex adhesive
- Stirrer or mixer
- ¼-inch notched trowel
- 1 ½-inch galvanized nails
- Hammer or nail gun
- Utility knife
- Fiberglass mesh tape
Wipe down the subfloor with a damp rag moistened in mineral spirits to remove surface dirt, dust and other contaminants that can ruin the bond between the new cement board and the surface. Allow the surface to dry completely before continuing.
Mix thinset mortar and latex adhesive additive as per the products' instructions. Starting in one corner of the room, spread the thinset across the floor in a space large enough for a single Durock sheet. Use a ¼-inch notched trowel to create small ridges in the adhesive.
Set your first cement board sheet in place with a ¼-inch gap between the edges of the board and the walls. Push down firmly on the board to apply equal pressure to ensure that it is secured in place. Wipe excess thinset from around the edges with the edge of your trowel or a damp rag.
Install 1 ½-inch-long galvanized nails around the perimeter of the board while the adhesive is still wet. Space the nails every 8 inches along the perimeter of the board. As the adhesive dries it will further secure the nails in place, firmly holding the board to the subfloor.
Install the next cement board sheet, spaced 1/8 inch from the first. Repeat gluing and nailing the sheets until all sheets are installed in the first row.
Cut Durock cement board sheets as necessary to fit in the installation area. Score the cutting line with a sharp utility knife, cutting at least halfway through the board. Apply pressure to the face of the board to snap it through the rest of the way. Smooth the cut edges with a fine rasp.
Stagger the joints of the cement boards in different rows by 16 inches to prevent weak lines running under the tiles. Simply cut 16 inches off of the first board in the second row to create the stagger effect. Continue to cut, glue and nail until all of the sheets are installed on the floor.
Fill in the seams between boards with the thinset mortar mix and immediately apply fiberglass mesh tape over top of the seams. This seals the joints and prevents shifting or moisture leakage between the sheets of cement board. Allow all adhesive to dry before doing any more work on the floor. Drying time varies by climate and product; some will dry within four hours, while others recommend that you wait at least 24 hours to ensure the best hold.
Tips & Warnings
- For flooring installations, the subfloor must be at least 5/8-inch thick and made of exterior-grade plywood. Countertops must be at least ¾-inch exterior grade plywood, covered with roofing felt.
- Durock cement board installed over countertops or walls does not need adhesive application. Instead, use galvanized nails to adhere the boards to studs or into the solid plywood base of the countertop. You must still fill in the gaps with thinset and tape.
- Cutting Durock cement board will produce a lot of dust. Always wear protective goggles and a dust mask when cutting.
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