How do you fill seams between cement boards?

Use special mesh tape on seams



Cut drywall to fill in between the existing wall or ceiling and the cement board. Screw the drywall to the studs. Cover all of the corners, joints and seams, including the joint where drywall and cement board meet, with the fiberglass mesh tape.

How do you fill seams in durock?





Cut fiberglass mesh tape to fit in a single layer over every joint where the panels meet, but do not overlap the tape. It’s OK if it’s an inch or two short in spots. The tape is self-adhesive and will stick to the Durock panels. Press and smooth the tape firmly in place.

Can you mud cement board?

The correct way to “mud the joints” is going to be to use tile thinset and a fiberglass tape made for cement board. It’s similar to the sticky fiberglass tape made for drywall, but its thicker and more abrasion resistant since the thinset has sand in it and can be vary abrasive.

Can I use mortar for cement board seams?

Fill the Joints with Mortar



Use the flat side of your notched trowel to fill the joints between the backer board sheets. Smooth the mortar so it extends about 1 1/2 inches on each side of the joint. The extra mortar will make it easier to embed the fiberglass tape.

What do you do with a gap between tub and cement board?

The best approach when installing cement board or other tile backer around a tub is to keep the cement board out of the lip area. Apply it to the wall with the bottom edge about 1/4 in. above the lip of the tub. Then apply a generous amount of thin-set to the bottom bathtub tile and position it 1/8 in.

What is mesh tape?





Mesh drywall tape has a tacky backing, allowing it to stick to the wall on its own. Paper tape needs to be embedded in a layer of joint compound. This makes mesh tape easier for the average DIYer to install on a flat length of wall. Most paper tape also comes with a factory crease in the center.

What kind of joint compound do you use on cement board?

For best results getting a good finish between cement board and drywall, use a setting-type joint compound. This product produces a better finish over mesh tape than all-purpose joint compound. Apply 2–3 coats of joint compound to the seam between wall boards. Wait at least 24 hours between coats of joint compound.

Can you use joint compound on durock?

Durock Cement Boards are a type of drywall reinforced with cement for a harder surface. This type of wall material can be finished just like ordinary drywall, using joint tape and joint compound.

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.

Do you tape Hardibacker joints?



For tile backer boards such as Durock, Wonderboard, Hardiebacker, Permabase, and others the seams between the board need to be treated with 2-inch alkali-resistant mesh tape. Then a coat of thinset gets flat troweled over the seam. What this does is tie the two boards together and help prevent flexing.

How do you seal Hardie board seams?

Quote from the video:
Quote from Youtube video: This area right here what you wanna do is you want to take some of the thin set mortar you want to just put it on the teeth and then sweep it off so that you get a nice thin layer on the teeth.

Can you drywall mud over cement board?

When using drywall compound over cement board, it is recommended, but not required, to use a faster setting-type joint compound (45 or 90 min), than typical joint compound. Make sure to follow manufacturer guidelines for the products used to finish the non-tiled area.

Can you use drywall screws on 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.

How do you finish cement board?

Cement board is an excellent choice for home renovation. But you need to be extra careful with the finishing.



  1. Step 1: Attach the Cement Boards to the Frame. …
  2. Step 2: Use the Mesh Tape. …
  3. Step 3: Apply Quick Set Cement. …
  4. Step 4: Time for Water Proofing.