I have a problem with a shower I built 3 years ago. It has 2 sides of glass block sitting on a concrete curb. The block was done with glass block mortar and plastic spacers (as in the recent article in FH). A few months ago, I noticed that the mortar was damp on the outside after using the shower. Upon further inspection looking up from the floor, I noticed dark areas that look like mold on the tops of several blocks. I also noted that some blocks appear to have cracks parallel to the edge within 1/8 to 1/4 of an inch of the edge.
I did not use grout on the joints, just the mortar. I sealed it with a penatrating sealer. So, now I’m wondering what to do about the mold, the cracks and how to better seal the joints.
Any thoughts and ideas would be welcome.
Replies
Sounds to me like there may be movement in the floor system under the shower. This may cause the mortar joints to develop cracks and allow water to infiltrate due to the movement. It may also cause individual blocks to crack because they don't exactly bend.
Was extra framing added to the floor under the shower? I learned that unless the block is laid on a slab foundation, you need to add additional joists under the shower area to hold deflection to basically zero because glass block can be very heavy and you don't want any movement.
Yeah, I was afraid that might be the problem. A hairline crack showed up in the vertical tiles on the curb. I guess I'll try to stiffen the joists. thanks.