Tiling Over Plywood

Tiling Over Plywood

Tiling over plywood for floors, and tiling over plywood for walls.

What’s the difference, and why do we need the plywood?

I read some posts earlier regarding tiling onto plywood.

I did a job just over a year ago. When I looked at it I advised that the 12mm wbp plywood was not a satisfactory substrate. The customers builder argued that it was and that he had been building bathroom & wetroom walls like it for years with no issues. We eventually reached a compromise where I had to tank the walls with a membrane (I used Porcelanosa Imperband) first.

The back wall area is 2.4m across, and the tiles were 930 x 330mm. I used Mapei Keraquick to fix the membrane & Mapei Keraflex to fix the tiles.
The pics below show a vertical crack that runs from top to bottom right down the centre of the wall, i.e. where the two plywood panels meet.

I explained the issues with regards to thermal expansion caused by rapid heating and high humidity in wetrooms, but the builder knew best :lol:. I now have to strip everything out and build the walls correctly using a tile backer board, then re-tile all at the builders expense.

I hope the above helps illustrate why plywood is not a suitable tile substrate for high humidity areas.

I’ve just moved house. In my previous house I had someone build me a fully tiled shower cubicle about 15 years ago. He used 18mm WBP on a 4×2 frame, a 1200x900mm shower tray with 3sided upstands under the tiles. Unfortunately, I don’t know what adhesives or surface preparation he used for the tiles.

It has never leaked and none of the tiles have ever cracked or fallen off in 15 years of almost daily use.

So it can be done . . . I’d just like to know how!

Just stripped out a tiled shower cubicle, the tiles were put onto plywood, and had an ok bond. Ive overboarded with Multipanel now but theres a half foot gap at the top that wants tiling with some porcelain tiles.

I cant really replace it with cement board for various reasons.

I have Primer G and Keraflex s1 already for the plastered walls as only seem to be able to get Mapei stuff around here.

What can I use to securely stick these tiles?

Yes I know its not ideal but I have no choice. Theres no other way. So need to figure out what people use to do it well.

The cubicle I had just ripped out was tiled by someone onto plywood over 15 years ago, and they wernt that easy to chisel off. Literally had to get the sds out in some places.

Ready-mixed non-slip water-resistant tile adhesive for walls
 Fixing ceramics (up to 300 x 300mm), mosaics and some Composition: Acrylic based organic dispersion
natural stone in dry or wet interior enviroments Colour: White
Restrictions: NOT Suitable for
 Exterior use or total immersion areas (e.g. swimming pools)
 Some non-porous tiles (depending on size / background)
 Bedding depths exceeding 3mm

Use for
 For domestic and commercial areas including
showers and commercial kitchens
showers / kitchens / bathrooms / wet rooms
of 3 days at 20’C before grouting

Domestic Showers (1)
Wet areas
⌃ May vary dependent on nature and flatness of surface and on trowel used
** Cured adhesive
(1) Do not use shower for at least 2 weeks follwing completion
of grouting – BS 5385: Part 4:2009,clause 7.2.1
(2) Provided surface is sufficiently flat
(3) Check suitability of sheets / boards for the intended purpose
with the manufacturer
(4) In frequently wet conditions tank out with BAL-WP1 TANKING SYSTEM
(5) Drying times will be extended, i.e. leave adhesive to dry for a minimum Recommended
Application Tools
Typical Coverage⌃
0.75m² / kg Round notched
Dry areas
0.50m² / kg Thin bed solid bed
Grout after: 24 hours (at 20’C)
Clay Brick / Medium Density Concrete (2)
Sheets & Boards (3) (4)
Rendering Usage: Bed-thickness / Time
20 mins 24 hours at 20’C
Temperature Resistance**
-30’C to 100’C
Usage: Tools / Coverage
Tile Backer Boards
Plasterboard (4)
Plaster (4)

  • Drying time will be extended in colder temperatures. When fixing to impervious
    backgrounds or when fixing tiles of low porosity

I have to tile over plywood boxed in pipes and will be using Bal one part flexible adhesive. The instructions state for timber flooring you should overlay with exterior ply and prime all timber surfaces on back face and edges with neat BAL BOND SBR priming agent. So my question is why do you have to prime the back face of plywood which will not be tiled and does that mean that I do not have to prime the front face which will be tiled.

Viewed a job this morning, , grout is cracking, customer wanted to know if grout could be scraped out and replaced, he thought it would be a small cheap job, on further investigation we found out so called tiler had tiled directly to plywood in shower area and onto floor with UFH (underfloor heating) i removed tile on shower wall, looks like its been dot and dabbed, whole lot in shower wall area needs to be removed and all the floor needs to be removed, this will mean trying to remove glass shower screen without breaking it, removing toilet, removing all controls and shower hose, destroying existing UFH and replacing with proper materials.

Do it properly in the first place and avoid these costly errors, builders please stop using plywood to tile onto, this can be the result. Now you know why tilers moan all the time!

The general public need to have a long hard look at themselves & carry out proper investigation into who they are going to employ for these jobs, look at Sparkle??
Saying that my ex business partner used to like to dab tiles on walls & floors & he’s still at it..

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