How to prep a bathroom floor before tiling?

Author: Kaci Hills  |  Last update: Saturday, July 5, 2025

A successful tile installation project requires a level surface.
  1. Check for dips in the floor by sliding a 4-foot to 6-foot straight edge in different directions all around the room. ...
  2. Fill seams in the subfloor with caulk. ...
  3. Sand down any uneven or high spots. ...
  4. Pour the liquid underlayment into any dips in the floor.

What should you put down before tiling a bathroom floor?

For concrete subfloors, use an unmodified mortar. For plywood subfloors, use modified mortar. Apply the mortar to the subfloor with the flat side of a tile trowel. Then comb over it with the notched side.

What is the 3/4/5 rule for tiling?

To get a perfectly square corner, you want to aim for a measurement ratio of 3:4:5. In other words, you want a three-foot length on your straight line, a four-foot length on your perpendicular line, and a five-foot length across. If all three measurements are correct, you'll have a perfectly square corner.

How do you waterproof a bathroom floor before tiling?

Seal with Silicone
  1. Using a caulk gun and silicone seal, fill the seams between the floor and the wall.
  2. Fill any cracks in the floor as well.
  3. Cracks and gaps will attract moisture, so sealing them completely is an important step in making sure your floors are entirely waterproofed.
  4. Allow to dry for 24-hours.

Does the entire bathroom floor need to be waterproofed?

The entire floor should be waterproofed for the shower area, and the shower walls need waterproofing up to 1800mm. Bathroom walls need waterproofing up to 150mm. For wooden bathroom floors or bathrooms on higher levels, the entire bathroom floor needs waterproofing.

How to Prepare Subfloor for Tile | The Home Depot

What is the best waterproofing before tiling?

Apply a Waterproof Membrane:

To provide an extra layer of protection, it's advisable to apply a waterproof membrane on the entire surface that will be tiled. This membrane serves as a barrier against water penetration and helps prevent any potential leaks.

Can you lay tile directly on a plywood subfloor?

Install an Intervening Sheet of Plywood

Do not install tile directly on the plywood subfloor itself.

Do I need cement board under bathroom tile?

One of the first questions that many people before installation is whether to use plywood or cement board under tile. While you can technically install most tiles on any smooth, clean substrate, using cement backerboard will give you superior results every time.

What goes between subfloor and tile in bathroom?

Underlayment is the material placed on top of the subfloor that assists in the installation of the tile or other type of flooring.

What are the golden rules of tiling?

The golden rule when installing tiles is install on a concrete floor where possible and always ensure it's level by applying a levelling compound beforehand – watch this video to find out exactly how.

What is the easiest tile to install in a bathroom floor?

WPC Vinyl is a combination of wood, plastic and vinyl tile, and is considered the easiest to install. This is because it's waterproof and is much more flexible and easy to work with compared to porcelain or ceramic tiles, which are brittle.

What is the best underlayment for bathroom tile floors?

Backer board is the most favored tile underlayment option when installing ceramic or porcelain tile. It comes in rigid panels that contain a blend of cement, fiberglass, and sometimes crushed glass particles. Bedding refers to installing a backer board on top of a layer of the thin set that acts as an adhesive.

Do you tile under or up to the toilet?

Unless you are in a situation where it is impossible to redo the floor tile due to the flange already being put in, never put the tiles below the existing toilet and the flange. Having the tiles go under the toilet makes it much easier to do repairs or removals.

Does mortar go under tile?

According to the ANSI and the TCNA Handbook, tile requires a minimum of 80% mortar coverage in interior applications, and 95% for exteriors and wet environments. Natural stone tile requires 95% coverage in all areas.

Can you just screw cement board to the floor?

Embed the cement board in latex-modified thin-set mortar

Then spread thinset mortar with the flat side of a 1/4-in. notched trowel and use the notched edge to “comb” the mortar. Embed the cement board and screw it to the underlayment with special 1-1/4 in. cement board screws spaced every 4 in.

Why use DiTra under tile?

The distinguishing feature of DITRA is the existence of free space created by the configured channels on the underside of the matting. The free space provides an escape route for excess moisture and vapor that could otherwise cause damage to the tile layer above.

Is it better to tile over plywood or backer board?

If you compare the two configurations using identical thinset mortars, tiles installed over cement backerboard have greater shear-bond strength than those that are installed over plywood.

How to prepare a bathroom floor for tiling?

Step-by-Step Guide on How to Prep for Tile Floor

For concrete floors, clean the surface thoroughly, repair any cracks with a suitable filler, and use a self-leveling compound to even out any uneven spots. This is how to level a concrete floor before tiling.

Does thinset bond to plywood?

Traditionally, you would use modified thinset to adhere tile to a plywood subfloor. Due to its absorbent and porous nature, plywood is capable of sucking the moisture out of unmodified thinset. Leaving less water in the mixture will allow for less hydration, and cause a weak bond between the tile and the subfloor.

Can you tile over drywall?

It is possible to tile over drywall where it is not subject to extreme humidity and is secure. It is not recommended to lay tiles over walls and areas subject to moisture, such as in showers. The water in these areas could eventually seep into the tile, causing damage to the tile, mold, or infestations.

Can you waterproof and tile same day?

No wait time is required. A water test should be performed before setting tile to verify a successful waterproofing installation. This evaluation may be required by building code officials and is considered best practice.

What is the cheapest way to waterproof a bathroom wall?

Bathroom waterproofing with liquid membranes is perhaps the easiest and cheapest modern method of waterproofing, which can be applied to any surfaces that come into contact with water or moisture.

Can you tile straight over waterproofing?

In conclusion, you can tile straight onto waterproofing provided the surface is non-porous and smooth. If you are tiling onto a porous surface, such as concrete, make sure to seal it first. And if you are tiling onto a rough surface, such as brick, make sure to smooth it out first.

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