Getting conflicting information from people on the next steps to get my shower project finished.

I have my cement backer board installed and its time to fill in the joints.
My father in law says to fill in all the joints with mortar and then tape but this doesn't make sense to me.

Wouldn't I tape all the joints and THEN apply the mortar?

Also is standard mortar OK or do I have to use thin set mortar?

The way I did it was, spread the thinset over the joint then tape the joint (the tape will stick much easier), then take a 4 in. putty knife and smooth out over the joint (that will push the tape into the thinset).  YMMV but that worked for me.

Thinset mortar first, this fills the voids and gives the tape something to stick to. Otherwise you will have tape peeling free PDQ.

Make VERY sure you use the correct glass tape that can live with the alkali conditions caused by the thin set. some people do this step as they tile to keep the number of bumps down. SS

Thanks fellows.

One more question.
Do I have to use thinset exclusively for cement board?

What's the downfall of standard mortar in this situation?

standard mortor can shrink and crack

Thank you.

I hit the jackpot at the local lowes, they had two full bags of thinset that contractor brought back and I picked it up for $5 a bag.

I'll have enough to even do my other shower.

   I use mastic instead of mortar.  The tile will be easier to adjust after 20 minutes

and there is no mixing.  Thinset is great stuff but the modern mastics are extremely strong

and will keep a good bond for 25 years plus.  

Taping corners and seams:  Do that as you set the tile.  You will completely eliminate any

high spots as the mastic will be soft when the tile is set.  Use mesh, not paper tape.

Backer board is not water proof and it will mold. Read the manufacturer data, it will wick 3x as much water 3x as far as drywall.





The old way was to install vapor barrier behind the backer.





I prefer to install the backer and redguard it. redguard is a brush/roll on water proofing anti fracture membrane. Very easy to use.





I actually prefer to skip cement backer entirely on walls and opt for denshield with redguard. The denshield lays smooth, cuts with a knife, is flush with the sheetrock, doesnt fall apart when you screw the edges, is already water proofed on the face, and it can be seamed with caulk instead of thinset and tap.





For full steam showers i go schluter.
If you tape use the correct mesh tape. Humps will make tiling very difficult. Do a little research on thinsets, if you use the wrong stuff you are going to have problems. They are not all created equal and for use in every application.

I thought using cement board was the new standard?

I ended up picking up some USG cement board mesh tape btw.

Green board (green sheet rock) is no longer code approved for wet locations, and it never should have been.





Many people use cement board as a replacement for green board , but they use it thinking that its water proof, and they use it a a magic cure all for all applications. In some cases its actually worse than sheetrock. The problem is that Home Depot and Lowes only carry Cement board for the most part, so that what many people use. Home depot now carries ditra, and some Lowes flirt with densshield.





Schluter is the new new standard. Even though its been around for 20 years.





Board with the membrane already adhered will be the new new new standard one manufacturers get it into production.