How to Prepare a Subfloor for Terrazzo Tile
Before you can install floor tile, there must be a viable subfloor that the tiles can adhere to. Follow these step-by-step instructions to prepare a wood subfloor for tilework.
Ensure that the subfloor is sound and not loose, warped or damaged. Ensure that it's clean and flat.
Use a straightedge to score the material and then snap to break it apart. Make large cuts with a circular saw. You can also use a drill with a masonry bit to make pilot holes – for such cut-outs as circular patterns and then hit it out using a hammer.
Note: Cement backer board can be cut with a carbide tip scoring tool, circular saw with a carbide tip (set saw for thickness of board) or mechanical Snapper Steelhead Shear.
Lay the backer board in a "brickwork" type pattern–meaning that sheets are offset. No four corners should meet at any point. Do not align sheet joints with subfloor joints. In a narrow hallway, the boards can be installed in a line.
Using a notched trowel, apply a leveling bed of thinset mortar over the subfloor and embed the backer board sheets into the adhesive. Spread the mortar to about 3/16" thickness. Add more mortar as necessary to fill sunken areas in. Lay the backer board according to the manufacturer's instructions. Many have a nailing pattern that should go face up–with a nailing pattern every 8" on center.
Fasten the backer board to the floor using proper nails or screws, as recommended by the manufacturer, every 8" around the perimeter and all supporting the studs. Keep fasteners between 3/8" and 3/4" from sheet edges and 2" in from sheet corners. Make sure that the nail or screw heads are not sticking up above the board surface.
Note: In some cases, you can attach the backer board joints using 2" wide glass fiber mesh cementitious alkali-resistant backer unit reinforcing tape (see product instructions – usually needed for wide areas). The tape will help disperse any movement of the boards and decrease the probability of popping or cracking tiles along the seams.
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