My Super Secret Way to Install Bathroom Floor Tile-Part 3

My Super Secret Way to Install Bathroom Floor Tile-Part 3

Cracked floor tiles are unsightly nuisances that unfortunately make a bathroom look crazy bad.

When I think of installing new gorgeous porcelain I dont imagine the floor breaking after only a few months. But this is a possibility if the wood subfloor isnt properly prepared.

My last post shared why I always use cement board on top of bathroom wood subfloors. Today youll see the ins and outs of how to dry fit HardieBacker on top of your bathroom floor.

Once this super awesome cement board is in place youll have a crack resistant foundation to lay any type of porcelain or ceramic tile.

Measure Your Bathroom Floor Dimensions

Youll need to measure the length and width of your bathroom floor. These dimensions will give you a rough idea of how to lay out your HardieBacker (or let you know if you can play a quick game of Twister, just kidding).

Keep in mind that the HardieBacker joints shouldnt rest directly on top of the wood subfloor joints.  Also, if you have to use several HardieBacker panels their 4 corners should never meet at one point as this will create a weak spot for tile to crack.

Our dimensions for this bathroom were 61 inches by 60 inches. This was awesome because the HardieBacker panels we were using were 60 inches by 36 inches and therefore wed only have to make one cut.

After looking at the wood subfloor layout we were able lay a full HardieBacker panel flush with the back wall where the vanity would reside. Sorry for the super bright light in the photo below, we didnt have the vanity light installed yet. Notice there is a 1 inch gap between the left wall and left edge of the HardieBacker panel. We decided to fill this in with thin-set since there wouldnt be foot traffic on that section of the floor.

Youll also need to consider how far to place the cement board into the doorway.

Our goal was to have the transition between the hallway flooring (hardwood once it got installed) and the tile in the bathroom directly centered underneath the closed bathroom door.

To make your new bathroom floor tile look good I highly recommend undercutting the door jam trim. This allows the HardieBacker and new tile to slip underneath the trim instead of butting against it (which doesnt look good at all).

We placed a new porcelain tile on top of the dry fit HardieBacker and slid it up to the door trim. Then Rob used his Bosch multi-tool to undercut through the door trim.

Voila, a perfectly cut space for the new tile to slide under. You may have to coax the cut trim piece out with a hammer and screwdriver or chisel but it wont take much effort. After all is said and done there should be roughly a 1 inch gap between the door trim and the bathroom wood subfloor if youre using 1/4 inch HardieBacker.

How to Cut HardieBacker Cement Board

Once you know the general layout of your HardieBacker  you can cut it to size. In this project we cut the waste pipe for the toilet because we wanted to have the toilet flange sit on top  of the tile. Otherwise, the toilet wont make a good seal with the wax ring and this could lead to a water leak that might ruin the floor & wood support structure (note, this leak will likely happen on a holiday or the middle of the night-i.e. anytime a plumber isnt working).

I placed the HardieBacker panel on top of the hole in the floor where the waste pipe use to be. I also ensured the panel was 1/8 inch away from the wall and the bathtub. Then I drew the outline of the hole on the underside of the panel from the basement.

I admit we were lucky to be able to do this but if your bathroom is on a second floor youll just have to measure the location of the hole and transfer these dimensions onto the HardieBacker.

To make a perfect hole in the HardieBacker I made a scribe from a sturdy piece of plywood. I then drilled two of the screws we were going to use to install the panel into the plywood. The screws will need to be drilled into the plywood so that the distance between them is the radius of the hole.

Drill the scribe into the HardieBacker panel so that one screw is in the center of the hole and the second screw sits on the edge of the hole. The screw that sits in the center can be drilled most of the way through the HardieBacker. The screw that is on the edge of the hole should just touch the HardieBacker enough to score it.

With the scribe in place turn it clockwise (or counterclockwise if youd like) and score the outline of your hole. Then, (and this isnt a super ninja skill but Id like to think so) turn the HardieBacker over and insert your scribes center screw into the small screw hole. Scribe the bottom of the panel like you did on its top surface.

Take a hammer and hit the center of the scribed hole. BAMMM. Youve got a perfect circle in your HardieBacker. High fives anyone.

I placed the HardieBacker panel on the floor and positioned it over the waste line. I dry fit a piece of ABS pipe through the hole in the panel to make sure all was good.

We only needed one more piece of HardieBacker to completely cover the bathroom floor.

To cut straight lines you should use a straight edge (like a level or drywall t-square) and a carbide tipped cement board knife. Youll have to make a few passes with the carbide knife and then you should be able to simply snap the HardieBacker with your hands.

Dont Be a Dummy Like Me

At the beginning of this post I said we wanted the HardieBacker to be in the door jam such that the transition between the tile and hallway would fall underneath the closed door.

Well apparently I must have missed my coffee break because I forgot to account for this.

So I had to cut a 1/2 inch strip of HardieBacker and place it in the door jam.

The dry layout of the HardieBacker is the first step in the installation process. The next move forward deals with using thin-set and screwing the panels to the wood subfloor.

My next post will walk your through this and Ill share a big tip I got from the HardieBacker technical support line.

The summary points of this post are as follows:

  • measure your bathroom floor dimensions
  • position the HardieBacker panels so their joints dont overlap the wood subfloor joints
  • cut the door jam trim to allow the new tile & HardieBacker to slide underneath it
  • use a scribe to cut perfect holes in HardieBacker
  • use a straight edge and carbide cutting knife to trim HardieBacker
  • dont forget (like me) to place HardieBacker in your door jam opening

I hope this post gets you one step closer to tiling your bathroom floor. If you need more information on this type of project here are the some links that I think will help


Leave a Reply