- 1). Vacuum the subfloor to clean off any debris.
- 2). Mix a batch of thin-set mortar, following the instructions on the packaging.
- 3). Cover the subfloor in one corner of the room with the thin-set. Apply enough thin-set to cover an area big enough for one sheet of cement backer board. After you've applied the thin-set, create ridges in the mortar with the notched edge of the trowel.
- 4). Place a cement board in the thin-set, leaving a 1/4-inch gap between the sides of the board and the walls.
- 5). Cover the next section of the floor with thin-set, and then lay a cement board into the thin-set. Keep a 1/4-inch gap between the wall and the cement board, and an 1/8-inch gap between the adjacent cement boards.
- 6). Install cement boards until you reach the next corner of the room. If needed, cut the sheets, using a jigsaw equipped with a masonry blade.
- 7). Install cement boards on the rest of the floor, using the same technique. When laying the boards, stagger the boards in each row so there's no point where the corners of four different sheets meet. If you need to cut holes for outlets or floor vents, measure and mark the location of the holes. Drill a hole with a masonry-tipped drill bit along the inside edge of the cut line, then cut the hole with a jigsaw, beginning in the drill hole.
- 8). Drive backer board screws around the perimeter of the boards until the screw heads are just beneath the surface of the cement boards. Space the screws every 6 to 8 inches, and place them between 1/2 inch and 2 inches in from the edge of the boards.
- 9). Fill the gaps between the cement boards with thin-set. Smooth the thin-set so it extends approximately 1-1/2 inches on both sides of the gap with the flat edge of the trowel.
- 10
Cover the seams with 2-inch vinyl-coated fiberglass tape. Press the tape into the thin-set with the smooth edge of the trowel. - 11
Cover the tape with a thin layer of thin-set, smoothing it out with the straight edge of the trowel.
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