Q. I’ve got a partially sunken tub and shower that’s got a mixture of different tiles. The tub is cast-in-place concrete and was hot-mopped with asphalt to prevent water leaks. The grout between the mosaic tiles is eroding slowly, but the wall tile grout is in very good condition. Is mold causing the tile grout to erode? Will the eroding grout cause leaks? Should I just demolish the tub and shower and start over, or is it possible to repair the grout? How do I stop the mold from growing in this gorgeous tub and shower area?
A. Oh, my goodness! Thanks for the photos you sent in. Your tub and shower is a work of art! By all means do everything possible to restore it. I cringe at the thought of someone hitting that masterpiece with a sledgehammer to take it out!
Sunken tubs like yours are a dying craft. There are still master tile setters that can form one and then cover it with expert tile work, but each year there are fewer of these talented individuals. There’s a very good chance that your tub and shower could be a major reason someone buys your home in the future.
Here’s a general note: Before you consider removing a specialty fixture from your home, always check with a knowledgeable real estate agent. In certain areas of the nation, there are communities with period homes that are highly sought after. A top-performing, experienced agent can tell you what buyers are looking for.
Now, regarding your sunken bath, if you’re not experiencing any leaks at this time, then the job is just going to be tedious. The good news is you can re-grout the mosaic tile and make it look brand new. Fortunately, there are modern tools you can use that will allow you to get the job done much faster than what it took in the past.
Let’s talk about the grout deterioration first. Mold and mildew are not the cause of the erosion of the grout. The black organic growth is more a nuisance and a cosmetic blemish than anything else. It’s hard to say what’s causing the loss of grout, as I don’t know when it started and how fast the deterioration progressed.
The sanded grout that’s between your mosaic tub tiles is just a mixture of extremely hard, fine silica sand and Portland cement. When mixed and finished properly, this grout can last for many decades with no deterioration. It’s possible the grout was defective from day one because a little too much water was used to mix it or the sponge used to smooth the grout joints was too wet.
The grout may have held up…