Tiling on unlevel concrete blocks.

[JonHead34]

Hi all

I want to tile over a small area of concrete blocks to provide a splash-back area for a sink in a garage/utility. The trouble is that the concrete blocks don't provide a completely flat surface for the tiles - some blocks protrude a couple of millimetres further out than others. Do you think it would be okay simply to trowel the tile adhesive on think to level out the differences or do I need to go to a bit more effort to prepare the wall first?

Many thanks for your help

Jon

 

[andyboyo]

what you could do is flatten the surface as best as you can with a cold chisel and secure a peice of 12mm ply to the wall which you can then tile over using the flexible adhesive and grout......just a suggestion!

 

[Nestor_Kelebay]

Jon:

I'd do the prep work to establish a flat surface. You might get lucky and be able to accomodate that problem within the thickness of the tile adhesive under the tiles, but you might also end up with tiling that looks like a mouthful of crooked teeth.

If it were me, I'd pop down to any hardware store and buy yourself some 1/4 inch thick straight wood molding and fasten it to the horizontal mortar joints on the area you want to tile. Those mortar joints should be about 10 inches apart, so you can use them as screeds to apply a 1/4 inch thick bed of thin set tiling mortar on the blocks between the wood moldings using an ordinary straight plastering trowel.

Once the thin set dries, remove the wooden screeds and fill in the recesses where the wood moldings were with more tiling thin set mortar.

Then, set your tiles with thin set mortar over that smooth flat bed of thin set mortar.

And, prior to grouting, fold a piece of sandpaper in half and use that to remove any thin set mortar that may have gotten squeezed up into the joints between tiles.

Or, at least, that's what I'd prolly do.

 

[JonHead34]

Thanks for the suggestions guys!

Yes, I agree that it's worth doing proper preparation first rather than just ploughing in and hoping it will work out okay!

Many thanks

Jon