Not only is thinset a critical component underneath cement board but the other critical component is the fasteners. And you won't have the fasteners if you are trying to install it over concrete.
Why do you need Thinset under cement 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 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 do you put behind cement board?
Use an appropriate waterproof or moisture-resistant backing material behind grouted tile or stone or segmented plastic or fiberglass tub and shower surrounds. Appropriate materials include cement board which has a cementitious core and glass mats on both sides to strengthen the board.Can you apply tile directly to cement board?
There is no need to install backer board on a concrete substrate—ceramic tile can be applied right over concrete, provided the surface is flat, smooth, and free of significant cracks.DUROCK Cement Board Do's and Dont's
Do I need to seal cement board before tiling?
Although most backerboards currently available won't fall apart when exposed to moisture and are somewhat water-resistant, they aren't waterproof. To prevent moisture from seeping through to the wood or metal studs beneath the tile, a barrier or sealant must be used on porous materials.What thinset do I use for 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.Can you use 1/4 cement board walls?
1/4" hardibacker alone is an unsuitable substrate for shower wall tile. If it were attached to properly waterproofed drywall, plywood, or plaster it would be fine. Think about it, one wayward elbow, knee, or hip bump and you may get flexion which would cause the grout (or tile) to crack.Can you use 1/4 inch cement board on floors?
1/4" USG Durock® cement board is an ideal substrate for floor and countertop ceramic tile installations. The 1/4" thickness helps eliminate transition trim when abutting carpet or wood flooring and minimize level variations with other finish materials.Do you have to put 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).What goes under durock?
Subfloor should be minimum 5/8" APA span-rated plywood or OSB with an Exposure 1 classification or better. Minimum 3/4" APA span- rated plywood or OSB with an Exposure 1 classification or better. Cover base with USG Durock™ Brand Tile Membrane, 15 lb. felt or 4-mil polyethylene and attach with 1/4" galvanized staples.How thick should thinset be under Backerboard?
Plan for a layer of thinset 3/16-inch to 1/8-inch thick beneath your tile. A 3/16-inch layer of thinset will be enough for tiles with a smooth back to bond the tile to the floor or backer board. For natural tiles with an uneven surface on the back, you may need to spread a 1/8-inch layer of thinset during installation.How long before you can walk on cement board?
This is normally 12 hours but may be up to 24 hours in some cases. After the mortar is dry the backer board is ready to receive the mortar for the tile.Can you lay tile directly on plywood?
Tile can be laid on plywood. But do not install tile directly on the plywood subfloor itself. Use an intervening layer of a sheet of thinner plywood.Can I use drywall screws for cement board?
You don't want to use regular drywall screws for cement boards. They can corrode, they can break down the edges of the boards, and they won't drive in flush properly. Use ITW's ROCK-ON and BACKER-ON screws instead.What kind of screws do I use for cement board?
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.What is the difference between Hardibacker and cement board?
HardieBacker is much more light, and it is also the best selling brand of cement board available. It is much cleaner because it does not have any glass in it. It allows for a smooth job with minimal mess. As a bonus, HardieBacker board has an EZ Grid pattern so you can cut perfect lines.What is the best thinset for Hardie board?
An unmodified thinset (Masterblend) is fine between the Hardi and the subfloor. Tara, The reason for the layer of thinset between the cement board and the subfloor is to fill the voids/gaps between the two. It'll keep the cement board from moving up and down. 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.What do I use to seal cement board before tiling?
The thin-set is a cement-based powder that you mix with water or latex additive to form a thick paste, which is used to seal the seams in the board and can also be used to set the tile.Do you have to mud and tape cement board?
The thinset and mesh tape are to strengthen the seams. If you are going to tile over the cement board, you should tape the seams.Should I wet backer board before tiling?
Wipe the surface of HardieBacker® cement board clean with a damp sponge just prior to adding mastic or mortar. This 2006 forum discussion also seems to anecdotally back up that wetting HardieBacker first is a known "must do": Hardi is thirsty, thirsty, thirsty. 
