How to Build a Bathroom, Part II

In my last post I walked you through my bathroom project up to the point of installing the cement board for subfloor and shower backer. So we will start from there today! I want to mention that out of this entire project, this is where I got one step "wrong" and couldn't reverse it. I'll get to that shortly. For now, on to backerboards.

When applying tile to the floor and the shower walls, your substrait will not be the same for both. On the floor, you want to use OSB or plywood under the cement board to hold the weight of people walking on the floor. On the shower walls, you only need cement board as it is strong enough to hold the tile, plus you run the risk of walls swelling and tiles cracking if you have a wood product behind cement board. Wood will absorb water and swell, cement board will absorb water and remain the same size. I chose OSB as my floor substrait, and Hardiebacker cement board from Lowes. I used coarse-thread screws to attach my OSB to the floor joists, spaced 12-16 inches apart. At this step, you want to do one of two things to adhere the Hardiebacker to the OSB on the floor: either mix some of your thinset mortar that you will use for the tile and spread a thin layer over the OSB, or apply a healthy dose of construction adhesive between the two layers. I chose the second option, using Liquid Nails brand adhesive before screwing the Hardiebacker to the OSB. This is important because you want your floor substrait to be one single unit. As your house shifts over time, you want each surface to move independently and if your OSB and cement board are not firmly adhered you can get cracks in your tile down the road. Once you glue or cement those two layers together, run screws through the Hardiebacker and into the OSB, using the specialized cement board screws that are coated and threaded for this use. Also, make sure you leave an 1/8" space between your Hardiebacker pieces. More on that next.

Here you see my two oldest getting in on the Hardiebacker action. You also see the plastic sheeting I applied as a vapor barrier between the studs and the Hardiebacker. One important note is that you want to off-set your seams on adjacent walls. My walls were easy as the cement boards are typically 5'x3', and since that's the base dimension of my tile surround I ran the side pieces vertically and the back pieces horizontally. The seams naturally were off-set. Now, here is the "wrong" step I mentioned earlier. I made the mistake of placing my Hardiebacker first, then dropping in my shower base. I was so excited at how perfectly the base fit. I'm not kidding, I had less than 1/8" clearance for it to slide into place. However, what I was supposed to do was place the shower base and drop the Hardiebacker over the flange of the shower base. This ensures that if any water gets behind the tile it will run down the cement board to the shower. By the time I realized this I couldn't go back, because I had already completed the next step:

You can see in this picture the shower base with the flanges inside the Hardiebacker. You can also see the seams have a thin layer of mortar over them, thus my inability to reverse any steps. Anyway, the seams on floor and walls need to have a layer of thinset to connect your board, similar to the concept of midding wallboard. Just as with the Hardiebacker and the OSB, you want all walls/floors to behave as a single unit. Before apply thinset over the seam, make sure you apply an alkali-resistant mesh tape to reinforce the bond and prevent cracking. The 1/8" gap between boards that I mentioned before allows the cement to fully adhere your seams. Some experts recommend using the mortar in your corners, and a few recommend using silicone caulk. I used caulking, as it allows some give between your walls which I believe reduces the risk of tiles cracking down the road. Once your Hardiebacker is on, your seams are mortared, and your corners are caulked, you are ready to tile.

This was my first attempt at real tiling. Since I hadn't tiled and wasn't sure what to expect, I started with my floor since there was no danger of the tiles falling off the walls! I purchased dry cement mix because I heard it has better long-term results, and it's 1/3 the cost. I recommend mixing only enough to do small areas at a time on your first attempt, or you will end up with a lot of dry cement. We used 12" tiles and 1/4" spacers on floor and walls. to achieve our desired look. For a detailed look at how to tile, I recommend using YouTube as a resource, as I did! Lots of good material out there. If you want another how-to, maybe I'll tackle tile in more detail later. For now, we move to the shower surround.

The most difficult part of a tile shower surround is getting the tiles level and plumb. After doing my research, I settled on the method of tracing a level line from left to right at the top of where my first row of tiles would be. Since I didn't have the Hardiebacker over the shower flange, I had the added challenge of the bottom tile having a slight inward angle. The shower base is also made to angle to the drain, so don't trust anything other than a long level and drawn or chalked lines to guide your tile placement. I started by adhering my first row of tiles and allowing them to set. After they were set for an hour or two, I ran a vertical column of tiles, following a plumb line I traced for guidance. With your perfectly level bottom row and a plumb column for reference, you will find that you simply start troweling in areas of mortar and following your spacers up the wall.

We placed a double row of 1" accent tiles above the fifth row. I tiled up to this point with the 12"tiles, applied the accent tiles, then continued up the wall from there. If you find that your spacers are too small or too large for a particular space, remember that tiles may be slightly larger or slightly smaller than average, and use shims or other spacers to make up for the difference. The key is that your grout lines are straight from bottom to top.

Notice that the tile runs to the ceiling? I wanted to avoid drywall above the tile so I simply ran tile to the ceiling, applying my ceiling drywall before tiling the walls. I really like this look, it makes the shower look bigger and allowed me to place my shower head higher on the wall.

I'll wrap up this project in Part III!