For that sort of area which is about average I'd recon on using a bag (25kg) and throwing any thats left. BALs figures are a bit optomistic and the mat will need more than if you were just laying tile with a thick bed/solid bed trowel.

The main thing is you should not be using Rapadset, you need Rapidset FLEXIBLE and a flexible grout as well to allow for expansion & contraction as teh tile/adhesive bed warms & cools. Single part flexi would also be OK unless you need to walk on the floor in a few hours. Also don't turn on the UFH for 28days to allow a full cure of teh adhesive.

What mat are you using, I like the Devi ones as the whole backing is adhesive so it stick well to the primed surface.

Jason

Just ripped up 20m2 of slate with Electric UFH, what a pain, you have to keep cutting the wires away and I snapped my Armeg tile removal chisel after the first three tiles

Jason

londonman wrote on Oct 8^th, 2008, 5:21pm:

I've got 4 x 7.5kg bags of BAL Rapid with Flex addative going cheap if you are interested, collect only, FLEET, near Farnborough.

God....I'd forgotten just how much I HATE tiling! In retrospecrt might have been better to get a pro in but I could see problems with logistics.  For example, l;aying down the UFH mat first in the cement then having to come back the next day to maybe lay the whole tiles.  Then another day to lay the cut tiles.  What does the panel think?  How practical for a pro?

Three rooms to do.  All with underfloor heating ranging from 3sqm to 1sqm.

Room 1 - roughly 3 sqm floor tiles.  Shower enclosure 1200x800 tiles to ceiling on two sides

Room 2 - roughly 3sqm floor tiles only

Room 3 - ahower cubicle - three sides 800mm - floor 1 sq m

I can see the benefit.  The only problem I see...but I'm sure you've a solution!...is that the mats have a couple of connections that are quite proud and so need the adhesive being built up to accomodate.  Too thick a layer of adhesive and the weight of the tiles will squidge it out resulting in the tiles being out of level?