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Installing Cement Board Underlayment For Tile

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Spreading The Mortar
cement board mortar
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Cement board is generally required as an underlayment to tile installations because it is resilient against moisture and impervious to penetration by liquid agents. It is made from a mixture of cement and sand , which is reinforced by an outer layer of fiberglass mesh.

An alternative to this is fiber cement board, which is similarly made, but which has fiber reinforcement which is integrated into the structure of the material. This allows it to be thinner than regular cement board, and it is subsequently used in places where height is an issue. Dens shield is another popular choice, made from water resistant gypsum board. All of these are installed in the same manner.

When is it time to hire a professional?

Difficulty Level: Moderate

Time To Complete: 1-2 hours depending on the size of the room and the cuts necessary.

Materials Required

  • Cement board or alternative underlayment material
  • Thinset Mortar
  • Notched Trowel
  • Electric Drill
  • Tape Measure
  • T Square
  • Utility Knife
  • 1 1/4” cement board screws
  • Goggles
  • Work Gloves

Spreading The Mortar

Mix the thinset mortar according to the manufacturers directions, and then begin to spread it along the subfloor using your notched trowel. Start at the corner of the longest wall in the room. If you are worried about getting adhesive on the wall you can tape it prior to proceeding. As you work, make sure that you used the notched edge of the trowel to create wavy grooves in the surface of the mortar. These increase the adhesive strength of the mortared surface.

You want to spread enough mortar for a single cement board sheet at a time. As you lay the first sheet down, make sure that the rough side is up, and that you leave at least 1/4” in between the material and the wall. When placing subsequent sheets leave a 1/8” gap in between them, which will be taped and mortared later.

Laying Out Various Tile Projects

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