How thick does subfloor need to be for ceramic tile?

Asked By: Eusebio Lezamiz | Last Updated: 23rd March, 2020
Category: hobbies and interests woodworking
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Tile installed over wood floor systems MUST have a minimum of 1-1/4 inches of solid material beneath it. This means you can have a 3/4 inch wood subfloor covered by 1/2 inch plywood, cement board, or approved gypsum fiber underlayment.

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Accordingly, what kind of subfloor is needed for ceramic tile?

The subfloor under the tile should be at least 1 1/8″ thick, with a minimum of 5/8″ thick exterior grade plywood topped by 1/2″ cement backer board.

Similarly, how thick should cement board be under tile floor? Cement-fiber, or similarly reinforced, backer board comes in standard 1/4 inch and 1/2 inch thicknesses. If you're installing backer board over an existing subfloor, 1/4 inch is sufficient. If you're installing backer board in new construction, attaching it directly to floor joists, opt for 1/2 inch sheets.

Additionally, can you lay tile directly on subfloor?

While you can lay tile directly over a concrete slab using thin-set adhesive, don't make the mistake of applying tile directly to a plywood subfloor. No matter how firm the subfloor; the plywood will expand and contract at a different rate as the tile, causing cracks to develop in the grout lines or tiles over time.

What is the best underlayment for tile?

Exterior plywood is an acceptable underlayment for tile and is preferred to interior-grade plywoods because the bonding adhesives used are waterproof. If water seeps through the tile installation to the underlayment, it will not cause the wood to swell, as happens with interior-grade plywood.

29 Related Question Answers Found

Do you have to put down cement board under tile?

If you're working over a wood subfloor, cement board is the right choice for your tile base. No matter what you're told at a home center, it's not a good idea to install tile directly over plywood, especially in a damp area like a bathroom.

Do you need underlayment for ceramic tile?

Underlayments are the support materials that lay underneath your tile on a floor. They sit between your subfloor (usually plywood) and your tile. They provide a water-stable base, make the floor more rigid (less chance of cracked tiles), and are better suited for tile adhesion.

How do you prepare a concrete floor for tile?

Start by sweeping your concrete floor to get rid of all dust and debris. Then clean with a wet mop of plain water. Use a few tablespoons of a degreasing cleaner in warm water and scrub the concrete with a scrub brush. Finally, rinse thoroughly.

Can you tile directly onto plywood?

While tile can be laid on plywood, do not install tile directly onto the plywood subfloor itself. Use intervening layers of two sheets of plywood.

Where do you start when laying ceramic tile?


Dry layout
Find the midpoint of each wall and snap a chalk lines on the floor. The line crossing at the room's center are the starting point of the tile. Lay a row of tiles along a straightedge more than halfway across the room.

How do you tile an uneven floor?

Lay a flat board over the tiles, paying attention to the uneven spots, and beat the board with a rubber mallet. This will drive the tiles deeper into the mortar; if more pressure is placed on low spots than on high ones, it can even out the finished surface of the tile installation.

Do I need to prime plywood before tiling?

Priming Wooden Floors
You must “overboard” floorboards with a suitable thickness of marine grade plywood (not the cheap “sheathing” ply you can get) - basically, the thicker the better (12-18mm), as this will give the floor more rigidity. The plywood surface will then be the surface to be tiled.

How thick should Plywood be under tile?

British Standards recommend a minimum of 15mm thick plywood to be used for over-boarding purposes (any less will not provide the rigidity required). This involves screwing a sheet of plywood over the top of the existing floorboards / chipboard or plywood to provide extra rigidity and a flat surface onto which to tile.

How do you tile over a rubber membrane?

Deck Mud. The rubber membrane in a shower installs on top of a thin layer of sloped mud that runs to the drain, and another layer of mud installs on top of the membrane to create the base for the tile. This is usually around 2 inches.

How do you stick tile to wood?


Glue, called mastic, is the least expensive method for installing tiles. Mastic adheres the tile directly to a wooden sub-floor, to a wooden back-splash or onto a piece of plywood.

What kind of plywood do you use for subfloor?

While OSB is the most popular structural panel, CDX plywood is the most popular type of traditional or "veneer" plywood. CDX plywood is like other laminate plywoods, but the outer layers of laminate are grades "C" and "D," which means they are cosmetically rough and contain many imperfections, thus lowering their cost.

Do you glue tile underlay?

// The underlay should be laid in a staggered (brick) pattern. For softwood floorboards, plywood and particleboard flooring, it is recommended that the underlay be glued to the floor with wallboard adhesive in addition to nailing.

Does Thinset stick to wood?

Specialty Thinset
Whatever type of plywood you are dealing with, you need to use a rated thinset mortar that is designed to be used with wood. Most thinsets are designed to only work with a concrete or fiber board underlayment, not with wood.

What do you use for bathroom subfloor?

Plywood as a Subfloor Material
Traditionally, exterior grade plywood has been the subfloor material of choice for many bathroom flooring projects. Plywood is made by gluing alternating layers of wood veneer. CDX plywood (¾”) in particular is used often because it has a high level of resistance to moisture and humidity.

How do you fix backer board to floor?


If you floor is solid then you lay the hardie down in a staggard pattern using adhesive initally and then screws. The adhesive is only there to fill potential voids underneath the board and not as an adhesive. Use a flexible adhesive both below and above the boards and screw the boards down at about 200mm centres.

Do I need plywood under cement board?

The Surface Below the Cement Board
Flooring: For ceramic tile floors, the cement board usually rests on a plywood subfloor (minimum 5/8-inch-thick exterior-grade plywood or OSB). (Some cement board products may not require the underlying membrane if the seams are properly waterproofed.)

Can you use 1/4 inch cement board on floors?

Floors. Both 1/4- and1/2-inch cement board are appropriate for floors. To install cement board on floors, cement board manufacturers mandate a 5/8-inch plywood subfloor or OSB underlayment. They also require a 3/4-inch subfloor where tile size exceeds 12 inches.