I get quite a few questions here concerning cracking grout on a shower bench. In some form or another people are mostly asking whether they should caulk or grout the outside corner, where the bench top meets the vertical tile on the face. The reason for asking me this, however, is what I will address in this post.
Most people begin with something like ‘my grout has cracked and now water is getting behind my tile and my bench is starting to swell, there was an eclipse, my dog has burst into flames…it’s a whole thing. Should I grout or caulk that?’
Unfortunately this happens a lot (the bench, not the eclipse or k-9 flames…), and everyone thinks about it backwards. It is not the grout (or missing grout) that caused water to leak into your bench and swell the framing, it was the swelling of the framing that caused your grout to crack. Tile and grout are not waterproof. The reason you have this issue is because your bench was not properly waterproofed before tile was installed.
Water will get behind your tile and grout, it’s completely normal. If your shower is properly waterproofed there will be no issues. If it is not waterproofed correctly the water will get into your framing and begin to make it swell. Once that happens it will cause grout to crack (the first sign), tiles may become unbonded or crack as well. Before you know it the sun disappears and your dog is your only source of light.
So if you have cracking grout on your bench you need to remove and rebuild your bench – because it is not properly waterproofed. I describe the process in my post about (…wait for it…wait for it…) How to build a shower bench!
If you have any questions feel free to leave them below, I answer them every day when I
sober up get off work. I will, however, head off some of the most common:
No, there is no magic product, not even silicone, that you can put over your cracking grout line to miraculously make it waterproof again. It never was waterproof.
Yes, if your bench grout is cracking you NEED to replace the bench, or at least remove all the tile, see what sort of substrate you have to work with, and properly waterproof it. You can normally use a topical membrane of some sort over your existing substrate to fix it. But you DO need to remove all the tile on the bench to do this.
If you do have a barrier behind your wall substrate there is no way to tie in the waterproofing on the bench to the waterproofing on the wall. However, utilizing a topical waterproofing membrane on your bench will still be better than whatever you may currently have under there.
So that’s it, if you have cracking grout on your bench it is because your framing is swelling, your framing is not swelling because you have missing grout. This also applies to most any missing grout in a shower – especially curbs. Water WILL get behind your tile – it’s normal. If your shower is properly waterproofed it is not an issue. If you need to learn how to properly waterproof a shower just click on the library tab at the top. If you have any questions at all just leave them below.