What goes under Backerboard?

For flooring, the backer board should be installed over a 5/8-inch thick OSB or plywood base. For countertops, use 3/4-inch plywood beneath the backer board. And for walls and ceilings, apply 1/2-inch or 5/8-inch backer board screwed directly to the wall studs or joists.

Why do I need thinset under backer board?





Thinset is going to create a solid surface under tile and prevent flexing that could lead to cracking. Using thinset between the backerboard and subfloor will create additional strength, fill in any potential gaps that exist and lessen the possibility of movement.

Do I need to thinset under Hardibacker?

The installation manual for HardieBacker suggests to embed it in thin-set and it should be installed over plywood. Thus I would suggest removing the current wood planks flooring, install a 3/4″ outdoor grade plywood, thinset and then your HardieBacker (screwed down).

Do you put mortar under cement board?

Use thin-set mortar when installing cement backer board. Thin-set dries slowly, allowing you to fix and readjust backer board sheets as needed. The ingredients in thin-set mortar ingredients are cement, fine sand and a water retaining agent.

What kind of thinset goes under cement board?

The cement board is then screwed into the plywood while the thin-set is fresh/wet. MAPEI recommends the use of MAPEI Porcelain Tile Mortar, MAPEI Large-Format Floor & Wall Tile Mortar or MAPEI Large Tile & Stone Mortar as thin-set under the cement board.

Do I need a decoupling membrane?





Uncoupling membranes are used to reduce stresses between a building and screed. When a screed is laid, shrinkage can occur or stresses in the main structure of the building reduce impacts resulting in cracking. Putting a membrane between the subfloor and tile can help to avoid this occurring.

Can I just screw down cement board?

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.

What is a thinset mortar?

Thinset or mortar (or thinset mortar, thinset cement, dryset mortar, or drybond mortar) is an adhesive made of cement, fine sand, and a water retaining agent such as an alkyl derivative of cellulose. Many thin-sets have latex and polymer additives in them designed to increase bonding strength.

What is a subfloor?

The subfloor is the foundation beneath finish flooring materials. On wood-frame floors, the subflooring provides a continuous structural surface over the floor joists. In basements and in homes with slab-on-grade foundations, the subfloor may simply be a concrete slab.

What do you put under Hardibacker?



Latex or acrylic modified thinset (complying with ANSI A118. 4). Dry-set mortar for use between subfloor and cement board only (complying with ANSI A118.

Can I use mortar instead of thinset?

Thinset is an adhesive cement used to secure floor and wall tiles to concrete surfaces. The word “thinset” is sometimes used interchangeably with “mortar,” because it’s a type of modified mortar made specifically for tile.

Does thinset stick to thinset?

You can put new thinset on top of old, but only if the old thinset is perfectly smooth and level. This is rarely the case once the old tiles have been removed. The best option to smooth out the old thinset and prepare it for new tiles is to grind it down.

Is back buttering tile necessary?



Although not necessary for tile coverage, back buttering can be effective by increasing the bond of the mortar to the back of the tile which is an excellent benefit.

Does vinegar remove thinset?

Vinegar acts as a simple acid solution when it comes in contact with certain elements, such as cement. While vinegar is a weak acid solvent and won’t damage dried concrete, it wukk help to loosen up the bonding elements of thinset cement, allowing you to wipe up limited dried residue with your sponge.

Does wetting thinset make it easier to remove?

Chipping Thinset Away with a Putty Knife. Pour 0.39 gallons (1.5 L) of boiling water gently over the thinset. Within 40 to 60 minutes of water application, you should notice cracks starting to appear in your thinset. This decreases its integrity and makes it much easier to remove using a putty knife.

What tool removes thinset?

An angle grinder is one of the best thinset and tile removal tools around. If you happen to have an angle grinder on hand you have used before for concrete grinding, try pairing it up with the stiffest metal brush attachment you can find.

What will dissolve thinset?



Start by mixing 1/2 of a cup of a citrus-based degreaser with a gallon of hot water. The hot water will help to soften the thinset just a bit, making it easier to remove. Pour the hot water on the thinset on the tiles, and be sure to use rubber gloves when doing so.