Project managed bathroom, en suite & downstairs loo installations

Incorrect Floor Preparation Prior To Tiling

It is vital that bathroom floors are properly prepared prior to tiling if the following is to be avoided.

Cracked Marble Floor Tiles With Bathroom Installation In Leeds

 

Introduction
  • We rip out a lot of bathrooms (roughly the same amount as we fit strangely enough!)
  • Ripping this bathroom out was prompted by the shocking state of the existing floor.
  • The marble tiles had cracked in a variety of places as you can see above.

 

Causes
  • Sub floor movement or stresses causes 90% of tile cracking and this is mostly due to incorrect preparatory work prior to tiling.
  • Please see here for more information.
  • The other 10% may be incorrect adhesive or grout used, or possibly a leak.

 

Remedy
  • Remove the tiles and examine the installation in detail.

 

Findings

When we chipped off the tiles we discovered that the tiles were laid directly onto chipboard (wrong!)

Chipboard should always be overboarded with a tile backer board or a decoupling membrane.

Removing Cushioned Chipboard Flooring With Bathroom Installation In Leeds

When we removed this chipboard we found that it was a cushioned chipboard that was merely floating on the plywood subfloor below i.e. it wasn’t even screwed down!

Chipboard With Acoustic Underlay With Bathroom Installation In Leeds

The cushioning on the back of the chipboard (used to provide acoustic insulation in flats primarily) was compressing whenever it was walked on (its made of the same material as carpet underlay.)

This was causing the whole floor to move, bend and twist, and this was causing the tiles to crack.

Tiles and tile adhesive (even flexible tile adhesive) cannot bend and flex to this degree and so something has to give and cracks form.

Deflection of the floor is particularly bad for natural stone floor tiles (rather than ceramic or porcelain floor tiles) as they have less ability to absorb movement – this is reflected in the deflection tolerances given for the 2 different material types outlined in this article.

Sodden Chipboard With Bathroom Installation In Leeds

Furthermore, these cracks let moisture in, and the result was a soaking wet, rotten, useless chipboard layer. (chipboard is very bad in wet environments – it turns to Weetabix in the presence of water.)

Plywood Base For Chipboard Floor With Bathroom Installation In Leeds

Luckily, the subfloor below this layer was solid floorboards overboarded with 25mm marine plywood screwed over the top so this was solid enough to start again from.

To re-do the floor, it was then overboarded and tiled by following the steps outlined here.

Lessons learned

Do things right 1st time and employ a professional if you are unsure as to the correct process for tiling – floors have a lot less tolerance for errors than walls do.

Thanks for reading,

Chris

Useful links

Tiling on Wooden Floors (Part 1 – Preparation)Tiling on Wooden Floors (Part 2 – Sub Floor Preparation)Tiling on Wooden Floors (Part 3 – Securing The Floor Covering)Tiling on Wooden Floors (Part 4 – Overboarding)

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