Tiling on new concrete floor that vibrates - glue/grout advice?

[mashie]

Hi
I'm about to lay porcelain floor tiles on a concrete screed in a new extension. No underfloor heating. The tiles are fairly small (50cm square / 50 x 25). Area is 7m x 3.5m.

Should / can I do anything to counter the noticeable vibration when I walk across the screed?

When I walk normally across the room, the bookcase rattles noisily (I'm under 10 stone). So I gather the raft is vibrating. It is on top of block and beam with a 3 foot void underneath, with proper foundations all meeting building regs.

The screed is new - insulated beneath and deep enough to meet building regs, topped up with about 1.5cm later because the builder got levels wrong. It's been down a year and isn't particularly dusty - I gather it shouldn't need sealing. It appears to be level. It has a plastic membrane sticking up all round the edges ie screed doesn't go right up to the walls (brick / plaster / timber). We'll cover the gap at the edge with skirting.

What sort of glue and grout should I use - I'm worried the vibation could lead to cracking grout or tiles. The tiles are ceramic.

All advice welcome. Thanks!

 

[u587162]

I’m just a home owner and not a builder but we’ve fitted a decoupling mat like a Ditra mat for helping with potential movement of the tiles for the reasons you mention.

 

[mashie]

Thanks - we've gone ahead now and laid them without a mat; maybe a mistake, haven't grouted yet (room doors delayed by six months so can't finish tiling). Decided it is the entire raft that vibrates so probably ok (ie floor is floating concrete slab and moves, but it presumably moves all in one piece).

 

[Mr Chibs]

The mat should only stop the tiling/grout from cracking... make sure you use flexible adhesives/grout.

I wouldn't have thought it should vibrate as much as you say... but I don't have experience of B&B floor. Out of interest, how thick was the original screed, before the top-up?