When tiling bathroom floor, I left a 1/4" gap between Hardiebacker and the tub wall. I'm planning to fill this with backer rod and silicone caulk.

I'd like to leave only 1/8" between TILE and tub for cosmetic purposes.

Once I add rod and caulk, can the tile go slightly over top of the backer rod and silicone to narrow that gap? Or should tile stop exactly where the Hardiebacker stops?

I'm new and this is a 2nd floor bathroom so I'm also planning to use Red Guard to be cautious.

1 Answer 1


I am assuming that you are placing ceramic tile. If you are saying that you have a 1/4" gap between your Hardiebacker and the front of the tub, Do Not fill with backer rod and silicone. That should be filled with the thinset you use to set your floor tiles. Even though it is a small area, the silicone and backer are flexible and a force on the edge of the tile can make it crack. if you are concerned about water infiltration from water down the front of the tub or on the floor, you can seal the grout after you are done, or use a grout that does not need sealed, ( Not my favorite type of grout.)
Red Guard is a good product. You can fill the gap with thinset. Let it dry. Tape off the tub, leaving just about 1/16-1/8" gap to the thinset. Apply your Red Guard and have at the tile the next day. When done your floor will be very waterproof to below under normal use.

Your Answer

By clicking “Post Your Answer”, you agree to our terms of service and acknowledge you have read our privacy policy.

Not the answer you're looking for? Browse other questions tagged or ask your own question.