Slate tiles on screed floor with UFH - tiles not sticking

[dvinchik]

Has anyone out there experience of laying slate floor tile on a screed floor with UFH?

We're just embarking on a tiling project with honed slate tiles on a screed floor - done when extension was built over 2 years ago.

We've got underfloor heating in the floor.

Can anyone give any tops tips of pitfulls to avoid?

We've stuck down the first few tiles, and they've not adherred, we'd forgotten to turn off the UFH - we're thinking that the adhesive has gone off too quick b4 tiles have chance to adher? Would that seem a sensible thought?

we're using a 10m toothed trowel and flexi adhesive.

 

[Richard C]

Well leaving the U/F heating on while you tile isn't going to do it any good at all.

What sort of flexi adhesive are you using? You say 10mm toothed trowel but what sort of trowel is it? You need at least a thick bed solid bed trowel - 20mm round notches 10mm deep @28mm centres or if the tiles are large, a large format trowel - 20mm round notches 13mm deep @28mm centres.

 

[dvinchik]

Well leaving the U/F heating on while you tile isn't going to do it any good at all.

What sort of flexi adhesive are you using? You say 10mm toothed trowel but what sort of trowel is it? You need at least a thick bed solid bed trowel - 20mm round notches 10mm deep @28mm centres or if the tiles are large, a large format trowel - 20mm round notches 13mm deep @28mm centres.

we're using a 10 mm square toothed trowel. The tiles are 400x400. we're using stone fix s1 rapid flex adhesive.

 

[tictic]

as rich has said the heat being on will be a factor.

did you sweep/clean the screed

did you prime it

did you back butter the tiles

have you got a decoupling menbrane down

 

[dvinchik]

as rich has said the heat being on will be a factor.

did you sweep/clean the screed

did you prime it

did you back butter the tiles

have you got a decoupling menbrane down

screed clean and primed - the adhesive sticks tot he floor

Didn't back butter tiles tho, UFH is water based one in the screed so don't need membrane i think.

 

[tictic]

//www.diynot.com/forums/viewtopic.php?t=247778