Joint Compound for Shower

[armycot]

I am installing a shower around a bath tub. I am using a mortar bed, installed over greenboard.

Is there any special type of joint compound I need to use on the greenboard before I apply the mortar to waterproof it?

I have not seen any specific recommendations on this.

[Fischer]

Don't use greenboard. Use DensShield. Greenboard will fail behind tile. It is not the backer of choice.

[armycot]

One clarification: I am not tiling to the greenboard.

I am planning on putting felt paper over the board, attaching wire, then floating a mortar bed to help square up the installation.

I want to know if I need anything special on the greenboard, prior to preparing for the mortar bed.

[pushkins]

If your using a mortar bed why not just staple up 4 mil plastic then nail up the mesh to the studs and float the bed.

If your certain this is the way you want to proceed then make sure you tape the drywall seams. Green board will not be waterproof.

[armycot]

Sounds good.

Thanks

[Fischer]

If you want to square up the shower, it may be much easier to simply put shims between the studs and the sheets. The local sheetrock suppliers and for that matter Home Depot stock shims to even out walls. The shims are 1 1/2" and come in 1/8" and 1/16", and they peel to make intermediate thicknesses.

Using DensShield would be a whole lot easier, waterproof, and only 1 application instead of greenboard, felt or plastic, mesh, and then floating. At the cost of what you're proposing it would probably be cheaper, not to even mention the time involved.