I am remodeling a bathroom to add a shower to a previously tub only bathroom. It is an older home (Built late 40's) and I believe the two interior walls are lathe and plaster the exterior wall I believe is cinder block with a plaster finish. The walls are not perfectly flat there is some minor bowing.

Can I apply the tile directly to the plaster without adding cement board? How much bowing is too much to fix with quick set? Any other words of advise?


2 Answers 2


You may not have lathe, but compressed board under the plaster and scratch coat. Either way; if plaster is any way compromised you should tear out to studs and start over. Bring plumbing to code; add a diverter and shower line in the wall; cover with cement board, tape off. Follow manufacturer instructions to a tee. Or, flatten walls with a latex modified skim coat product. When dry, waterproof with Custom Building Products Red Guard or better, Schluter Kerdi. Do not use type 2 mastics with these products. Please follow instructions properly. Showers see more water than a rain forest. Showers are labor intensive. Do it right the first time. Hope this helps.


Anytime you have to open a wall in an older home, you are opening a can of worms. You would probably save money in the long run by getting a licensed, insured contractor on the job. Once you open the walls, you will probably need to upgrade the plumbing, electrical, and insulation to modern standards. Also, check the thickness of the walls.

A friend of mine opened up old 1940s walls and found the studs were much smaller than 2x4s, and had to replace all studs and joists as well as all plumbing, electrical, and insulation. It was essentially a gut-job from ground to roof. Wishing you the best.

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