Rock and Wood

HOW TO PREPARE SUB-FLOORS FOR TILING

Jamie RobinsComment

Ceramic,  porcelain and natural stone tiles are all very different, so you must take great care in preparing your subfloor before laying your new tiles and things can go drastically wrong if you ignore these basic rules!  

Beginning with the best subfloor or underlayment materials for tile.

Cement-Based Backer Board

Backer board is designed for tiling. Backer board can be fixed directly over floorboards in your bathroom or kitchen floor and goes under various brand names, such as Hardy Backer, NoMorePly and others are available. See websites such as www.tilefixdirect.com and www.insulationsuperstore.co.uk for examples and advice on installing. They provide a sturdy base for you to tile onto and can also be used on walls to hang tiles onto for showers etc.

Tile backer board is always a preferred ceramic tile underlayment.

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Exterior Grade Plywood

Exterior plywood will also accept tiles and stone, without swelling up like interior-grade plywood.

Since cement board is cheap and easy enough to lay down on plywood, it makes little sense to skip this step. However, if you would like to install tiles on plywood subfloor, it is possible.

If you are going to attempt the work yourself Its a good idea to check out tiling forums to get advice, (www.tilersforums.co.uk) but we always advise our clients to employ a professional tiler with experience in carrying out this work.

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Concrete Slab

A Concrete slab or concrete screed is a good tile underlayment. Be careful of the expansion joints. If you tile over the expansion joints, the tile will crack eventually. To reduce the possibility of cracking, use an intervening material called uncoupling membrane. See our other Blog called THE IMPORTANCE OF USING DITRA MATTING for further advice.  

An uncoupling mat disconnects tile from its concrete subfloor. Because concrete can crack, these cracks transmit the same to the tile above. Uncoupling membranes effectively break this transmission domino effect..

Available under the brand names Schluter Ditra or Bal Rapid mat, this product is sometimes called anti-fracture membrane, crack isolation membrane, or crack suppression membrane.

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Poured Concrete Screeds

Always ask your builder for advice on what kind of screed has been poured before beginning your tiling. If it was poured there is a strong chance it may be a Hydrate Screed. Hydrate Screed - Once the screed starts to dry out it will leave a milky film (latent) on the surface which 'must' be removed before any surface finishing or decoupling membrane is laid.

Ask your screed company and tiler for advice here, it is really important, as you will need to apply at least two coats of acrylic primer to the screed before tiling or membrane. If you do not do this there is a risk that the chemicals in the hydrate screed or latent may react with your adhesive and prevent the tiles adhering to the screed. Something you do not want to happen!

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BIG NO NO's and DO DO's

  • NEVER tile onto 'standard' plasterboard that has been installed in shower areas! always insist that your builder or tiler uses a backer board of some kind. Plasterboard and water dont mix!
  • ALWAYS look for suspicious cracks in your screed or concrete slab. Consult your builder or tiler about them and question if its safe to tile over them? Use a layer of BAL Rapid mat to bridge small hair line cracks to be on the safe side.
  • ALWAYS use good quality 'flexible' tile adhesive. Good brands are Mapei, Ultra and BAL. try Ebay for some good prices! Especially on Ultra tiles adhesive.
  • ALWAYS prime your subfloor or walls with a suitable primer before tiling. BAL Acrylic primer or SBR and take advice of how to apply them from your builder or tiler.
  • If your unsure, and need a 2nd or 3rd opinion on something, then get them!  its an expensive and heart breaking situation to be in if something goes wrong and you have to start again! TRUST your gut feeling if someone tells you something and your not sure its correct....

CALL us at Rock and Wood for FREE advice anytime. We are here to help! 0845 4660192