Q: My master bath shower has a βsnailβ entry with glass blocks comprising two sides of the entry. A few of the glass blocks on the bottom row have gotten mold or mildew in them. Since the glass blocks are sealed, how do I get at the mold in order to clean it out? How did it get in there to begin with?
A:Β If the mildew is indeed inside the block itself and not in the surrounding mortar, the block has likely lost its seal and would need to be removed and replaced as there is no way to gain entry to the interior of the block to disinfect and reseal it.
If the mildew is in the surrounding mortar joints, the mortar will need to be scraped out, the area thoroughly disinfected then re-mortared. After the mortar cures, it will require a couple coats of a good silicone sealer to protect it.
Weβve seen a lot of glass block shower enclosures with moldy mortar around the blocks, but canβt say weβve ever seen a block with the mold on the inside of the block itself. Theyβre typically pretty tightly sealed at the factory. So take a good look at the area because what you may be seeing is the mold in the mortar as seen through the edge of the block, not inside the block itself.
These repairs are not the normal DIY kind of project and should be done by a licensed tile installation company that uses glass block in the normal course of their shower tile work, or a good masonry contractor familiar with this situation as an alternative. Glass blocks are very durable, but if not dealt with carefully, they can break and cause flying glass particles, so this kind of repair is not something we recommend homeowners undertake.
For more do-it-yourself tips, go to rosieonthehouse.com. An Arizona home building and remodeling industry expert for 25 years, Rosie Romero is the host of the syndicated Saturday morning Rosie on the House radio program, heard locally from 8-11 a.m. on KNST-AM (790) in Tucson and KGVY-AM (1080) and -FM (100.7) in Green Valley. Call 888-767-4348.
