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How to Install Bathroom Floor Tile: Part 2

Do you want to change how your bathroom looks but don’t know whether you can do it yourself?

The last post described how we prepped my brother-in-law’s wood subfloor for porcelain tile. Today we’re going to share how and why we chose HardieBacker as a tile underlayment.

Why should you care about HardieBacker cement board? Bathroom floor tiles are beautiful but without the right substrate, they will eventually crack and allow moisture to invade your wood subfloor.

So in order to avoid these painful scenarios, you’ll want to understand some of the basics involved when using a product like HardieBacker.


HardieBacker Before Tile Floors

We’re not afraid to share products that we personally use. HardieBacker is a product we’ve installed several times for both ceramic and porcelain tile projects.

HardieBacker Cement Board for Tile Installations

Here are some benefits of using HardieBacker:

  • Composed of cement which isn’t a food source for mold
  • Contains Moldblock technology that prevents mold formation
  • Comes in 3′ by 5′ panels that are light and easy to handle
  • Has 1/4 inch and 1/2 thick panels
  • It can be cut easily by scoring and snapping
  • High compressive strength, meaning tiles laid on top won’t break when stepped on
  • Doesn’t contain asbestos, formaldehyde, fly ash, or fiberglass
  • Moisture resistant and suitable for tub or shower surrounds
  • Can be applied over wood subfloors or floors covered with vinyl products

So those are all the reasons we used HardieBacker for tile floor project. Sometimes it makes sense to use an uncoupling membrane like Schluter DITRA – so keep that in mind.

Choose the Right Thickness of HardieBacker

You should use 1/4 inch thick HardieBacker for floor tile applications unless 1/2 thick panels are needed for transition purposes between adjacent rooms.

One HUGE question to ask yourself is “How thick will my new tile floor be?”.

You’ll need to do this to make sure the bathroom floor transition in the doorway won’t be awkward.

You absolutely don’t want to get done tiling then realize there is a 1/2 inch difference between the height of your new tile and the carpet in the hallway (at this point you’ll definitely let out a curse word or phrase)


Make Sure Your Subfloor is Structurally Stable

Our bathroom tile installation dealt with placing HardieBacker over a wood subfloor that was composed of two layers of plywood approximately 7/8 inch thick.

The installation guide for 1/4 inch HardieBacker recommends having wood subfloors made of 5/8 inch exterior grade plywood or OSB (oriented strand board) that is 23/32 inches thick.

So how the heck do you figure this out?

You can do this one of two ways. The first is to take the air vent off the floor and see if you can measure the floor thickness.

The second sure-fire way to determine the thickness of your wood subfloor is to use a hole saw to take a core sample. You can buy a 1-inch hole saw used to drill out deadbolt holes for door installations and use it for this project. We recommend getting a hole saw kit that comes with a starter drill bit.

Use a 1 Inch Hole Saw to Determine the Thickness of the Bathroom Wood Subfloor

Drill for your core sample in the center of a wood subfloor panel. This will ensure you don’t drill into a support joist below.

Take a subfloor core sample in the center of a wood panel

The last post in this series also discussed looking for any damaged subfloor. We closely investigated areas near the vanity, toilet, and bathtub for any signs of prior water penetration.

Damaged or irregular subfloor panels need to be fixed or replaced.

How to Determine the Layout of HardieBacker for a Bathroom Floor

The first step in determining your HardieBacker layout is to identify all the wood subfloor joints.

Identify all wood subfloor joints

Make sure to stagger all the HardieBacker joints so they don’t align with your wood subfloor joints. You’ll also want the HardieBacker to never have four corners touching each other. In other words, HardieBacker corners should never meet at one point and make a perfect quadrant.

And finally, allow for 1/8 inch gaps between HardieBacker board edges, walls, and cabinet bases.

Summary Notes for HardieBacker Installation on a Wood Subfloor 

We hope this post sheds light on why we like HardieBacker for some tile projects. After reading this today you should feel more prepared to tackle any floor tile project.

I put together the summary notes below to break down the tutorial even more:

  • Determine the thickness of your new tile floor
  • Ensure the transition between the new tile and adjacent flooring isn’t awkward
  • Take a core sample of your wood subfloor (in the center of a wood panel)
  • Inspect wood subfloor panels for damage
  • Don’t align HardieBacker joints on top of wood subfloor joints
  • Don’t allow 4 corners of HardieBacker to meet at one point, stagger the panels
  • Allow HardieBacker to have 1/8 inch gaps between board edges
  • Allow HardieBacker to have 1/8 inch gaps between walls and cabinet bases

What’s Next

If you’re doing a bathroom remodel and need help, join one of our online courses – they’ll make your bathroom renovation much easier!

Let me know if you have any questions and I’ll do my best to help.



Floor Tiling Tips