Often asked: How To Lay Concrete Board?

Do you have to put Thinset under cement board?

Thinset is absolutely required beneath backer-board on a floor. Also, backer-board provides no structural strength at all. You can not install it directly over a 1x subfloor; that is way too thin and will deflect.

How do you install cement board?


  1. Plan the Installation. Make a rough plan for the cement board sheet layout, based on the area to be covered and the size of the cement board sheets.
  2. Mix and Apply the Mortar.
  3. Install the First Sheet.
  4. Add Subsequent Sheets.
  5. Make Cement Board Cuts.
  6. Install the Remaining Sheets.
  7. Tape and Mud the Joints.

Can you just screw down cement board?

Screw and Joints

Do not use drywall screws as they are not recommended to be used to hold the backer board in place. All of your backer board pieces should be cut before they are placed on​ the floor. Along the perimeter, screws should be installed at least ½ inch from the edge, but no more than 2 1/4 inches.

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How do you thinset cement board?

Scoop up thinset on the flat edge of a 1/4-inch, square-notched trowel and spread the thinset across the plywood. Cover an area large enough to place the first backer board sheet. Apply another layer of thinset over the first, using the square-notched edge of the trowel.

What do you put on seams of cement board?

Use special mesh tape on seams

Cover all of the corners, joints and seams, including the joint where drywall and cement board meet, with the fiberglass mesh tape.

How long should cement board screws be?

Cement board attached to plywood or similar underlayment will hold with only 1 1/4-inch screws; for thick or heavy metal fixtures, use 1 5/8-inch screws. In general, 1 1/2-inch galvanized nails will hold the board firmly in place.

Can you use cement board in a shower?

Cement Board and a Sheet Membrane

Kerdi can also be installed directly over standard drywall in a shower because, when installed correctly, it creates a continuous waterproof barrier.

Do I need to seal cement board before tiling?

Contrary to popular thought, tile and grout are not waterproof, and some moisture will penetrate even if sealant is used. However, if you choose to use concrete backerboard, which is much stronger and more durable than gypsum board, a water vapor membrane must be placed underneath it or a sealant applied on top of it.

Does cement board need to be waterproofed?

So, if you’re looking for durability and strength, concrete backerboard will probably be your choice. First, you should provide a waterproof/resistant membrane against the wood studs before installing the concrete backerboard to protect the wood studs from moisture absorbed through the backerboard.

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Is it OK to walk on cement board?

You need to fasten the backerboard before the mortar sets up underneath, so walking on it while it’s wet isn’t a problem. start your screws in the center and work outwards, working once sheet at a time.

Can you glue cement board to concrete?

Technically, cement board can be laid over a concrete slab as the base for a tile installation. A better solution is to prepare and resurface the concrete slab so that it can accept thin-set adhesive or a mortar base onto which to lay tile.

Do you tape the corners of cement board?

If you are going to tile over the cement board, you should tape the seams. If you just want to leave the corners untreated that will probably be fine, because that seam won’t split the center of a tile.

Can I use deck screws for cement board?

It’s best to use the cement board screw, but a deck screw will do just fine. Use screws designed for cement board like Rock-On screws. They start easier than drywall screws in CBUs. They’re easier to use, don’t rust as easily and hold better.

Can I use drywall mesh tape for cement board?

FibaTape Drywall Tape for Cement Board

FibaTape® Cement Board Tape is a patented alkali-resistant fiberglass mesh drywall tape, and the only tape that should be used for cement applications with dry or thin-set mortar.

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