Adhesive thickness

[davey76]

Hi Guys

Following on from this thread: http://www.diynot.com/forums/tiling/reuse-floor-tiles.311291/

We have lifted the tiles and are filling in the wooden section of floor with concrete. We haven't lifted the tiles on the original concrete section of floor

Question: How much gap should we leave between the bottom of the tiles and the concrete for adhesive ? Obviously we need to level the tiles we are relaying with the tiles that are still in place

Hope that makes sense and thanks in advance

 

[Richard C]

Floor tiles must be laid on a thick, solid adhesive bed (or they will crack under load & the depth of adhesive will depend on how flat the floor is, the size of the tile & size of trowel used. From your other thread, 36” x 18” tiles are very large format & should be fixed using a large format trowel - 20mm round notches, 13mm deep, at 28mm centres which will give an adhesive bed 4-6mm thick. Using a smaller thick bed trowel - 20mm round notches, 10mm deep, at 28mm centres (tiles up to 30 x 30cm) will give an adhesive bed 3-4 mm thick but you will almost certainly need to back butter your paving slabs to ensure 100% adhesive coverage under the tile unless the floor is VERY flat. I would allow for 6mm & go from there but test before you start laying as it’s going to be trial & error if your trying to level to tiles which are already laid.

I would advise you use either an expansion joint or grout with silicone where the two floors meet otherwise it will crack.

 

[davey76]

Thanks Richard

Would it be an idea to leave a bit more - and then put a layer of SLC on top of the concrete to get up to the correct level ?

Point noted re. the expansion joint - I think the 2 slabs will join across the middle of a tile so not ideal from that viewpoint

 

[Richard C]

Would it be an idea to leave a bit more - and then put a layer of SLC on top of the concrete to get up to the correct level ?

You can do it either way. If you can get the new screed perfectly flat, which you will need with such large tiles, then fine; if not go for a thin SLC over the top to level it up. If using conventional sand/cement screed, don’t attempt to SLC or tile until the screed is cured & dry – 1 day per mm depth & a minimum of 28 days.

I think the 2 slabs will join across the middle of a tile so not ideal from that viewpoint

In that case you will probably get a crack across the tiles.

 

[davey76]

Thanks