How do I repair and waterproof plaster walls around a tub ?

My family replaces tubs for a living. That's all they have done for 20 years. The plaster is porous. It has drawn the water into the wood behind it. Trust me. Cut a small square out of the wettest area and peer behind it with a flashlight. You'll see discolored wood and sometimes MOLD. Happens all the time. If you repair the plaster with a patch, the underneath will never really dry out. So when you tile over it, in a short time the tiles will begin to fall off because that moisture behind the plaster will begin to work it's way back into the plaster and expand the wall. Then you'll have to remove all the tike, cut out the portion if the wall that's wet and replace it with properly graded wallboard and start again. My family makes it's living at this lousy job. And they always say, "if you have tile, the grout is always porous! It absorbs water unless you seal the grout and reseal the grout periodicaly"...... I'd strongly revimnend replacing the plaster with proper wallboard first, and then proceed to do a job well done. In the long run, you'll save money by solving the problem and arresting further damage to your wood framing and the floor beneath it!

I redid my bathroom, replace an old clawfoot bathtub with a one piece shower stall and I used the drywall thats waterproof, moldproof and then after using that I finished it off by using a Paneling made for bathrooms that help seal away the moisture. I bought the Drywall at Lowes home Improvement store.

Replace your plaster or drywall with cement board and then tile.

Thanks. I've been told that there are several ways to waterproof the walls. Maybe not.