I'm in the process of re-tiling my bathroom shower wall and I'm stumped on how to properly tile the window sill near our shower. Here's a picture:

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It's roughly 3 inches deep and 18 inches wide. We want to install subway tile for the walls and the tile we've selected is roughly 2.5 inches tall (which is obviously too small for the sill).

What is the preferred way to handle this? Should we use an entirely different shape of tile for the sill?

3 Answers 3


First, make sure the rough sill slopes toward the shower. Measure it with a level; if it's not appropriately sloped, build it up with more mortar to create the requisite slope.

Then, once you've painted all that cementboard with RedGard, the whole assembly should already be waterproof. Just tile over RedGard on the sill however you like. Any water that gets behind and under the tile (and it will) with harmlessly drain down the wall. If the tiles are too big, cut them. Or use dedicated bullnose tiles, which may be the right size and are likely to have a nice lip to them.


Use your subway tiles, just use two instead of one. Cut them so you split the difference on the width so they are the same size, rather than using a full tile and a cut strip.


Cover wood sill with red guard or equivalent. Install concrete board over sill; going through the trouble of getting it to slope slightly towards shower by building up mortar under it is not a bad idea. Do not red guard the cement board so the thinset has a good rough surface to adhere to. Install tile sloped towards shower by building up thinset on back to get the tile to slope. Try to make sure you do not have large gaps along the edges of the tile at the casing and the window. Make sure sill tiles extend over wall tiles. Then make sure the window casing tiles extend over the sill tiles. 100% silicone caulk all edges of sill and casing. (If the caulk can be cleaned up with water, it is the wrong stuff.)

Make sure to mix you thinset and grout correctly by not adding to much water and mixing them thoroughly.

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