Durock meets Greenboard seams / what to mud with ?

[cccgolluzram]

Never posted here before . I put new Durock up in the shower , the rest of the bathroom is new Greenboard . What would you mud the seam with - Thin set or Drywall Compound wherever the two meet ? Before you answer , let me explain that the seams I am concerned with are where the tile will end and transition to the painted walls .

Basically the seam would be under the bullnose tiles , but I am worried that using the thinset will cause the mortar to be exposed too far past the seam or bullnose tiles , into the painted area . If I use joint compound at this seam , it wouldn't be directly affected by water , but I worry that it is still too close to the wettest area . From where the bullnose ends , I only have 2 inches to play with from where the medicine recessed cabinet opening is and the bullnose ends . Could I use the Joint compound or go with the thinset and make it work ? The joint on the plumbing side is only 3 -4 inches outside the tub . What's the best course to take . The old walls were all greenboard under the tile with compounded joints under the tile .

Thanks - C. Marz

[Paul Franklin]

Here's what I do in that situation, but it may not work out for you. I plan it so the joint is about 1/4" behind the last tile. I don't mud or thinset the joint at all. The tile is attached only to the backer board, by holding the thinset back from the edge of the tile enough that it doesn't end up on the greenboard. When I grout the tile, I don't allow the grout to enter the edge between the tile and greenboard. Any that does get in there I clean out before it sets. Then, I caulk that joint later with urethane caulk (after wall is painted). The two different materials are going to move relative to one another. This method allows for it.

For this to work, you've got to have the joint in the right place, and it's got to be a neat joint without big gaps.

HTH,

Paul F.

[benick]

Sheetrock Brand Durabond Setting Type Joint Compound. It comes in a bag with varying setting times..45,90,210...You mix it in a CLEAN joint compound bucket with CLEAN water with a drill and paddle. Make sure paddle,tools,bucket are cleaned BEFORE it sets.And yes the durabond on the paddle WILL set up HARD submerged in a bucket of water..LOL...Keep in mind that Durabond CAN NOT BE SANDED so don't get carried away and ONLY use it to embed the tape. Finish with regular joint compound...I use Durabond to put ALL the tape on in a house as well as the first TIGHT coat on the cornerbead..I don't get callbacks for cracks...LOL...

[Colbyt]

I agree with this post.

I used Durbond 10 years or more on the exact same project the OP posted about to finish the joints where the concrete board met the drywall. There has never been a problem.

I did the tape bedding and first top coat in Durobond and then used regular setting sandable mud for the finish coats.

NOTE: You can not sand Durobond. It is a great time to master the less is more concept.