I've installed the under floor heating mat onto Matrox insulation boards in a small bathroom (2.7 square meters) and pondering about the pro/against of using a self leveling compound prior to tiling or tiling directly on top of the mat with suitable adhesive.
This is what I've found out so far:
PRO Self Leveling compound:
1) the smooth surface helps using notched trowels so tiling should be easier
2) acts as a protective barrier while tiling - eg. one can walk on it while while extra care would be needed when walking directly onto the ufh mat (in fact it should be avoided altogether).
3) it should help on the long term - e.g. if a tile need to be replaced, the extra layer of SLC should provide an horizontal key for the chisel and the cable are better protected.
4) air pockets are less of an issue with SLC as is more penetrating than adhesive - so the cable are more efficient.
5) easier to rectify tiling mistakes on the spot (while tiling) - if I discover that a tile isn't level later on it can be removed without damaging the cables....
Against SLC:
1) the extra layer of SLC mean a thicker layer of mass between the heating cable and the tile(at least 5mm for SLC and 3mm for adhesive = 8mm) - this way the heat has to travel more to reach the tile so it would take longer....I guess without SLC it is possible to lay 5mm thick adhesive (the heating cable are 3mm thick).
2) extra building costs - - fortunately the area in question is relatively small (2.7 square metres) so only 1 bag of SLC is required (£15 extra).
3) extra work - there is an extra stage to be added (though this might be compensate by the fact that tiling is easier when SLC is used).
Right now, I'm thinking of using SLC - point 4 and 3 of the PRO section above are very relevant in the long term...beside, this is my first UFH and tiling project so it's maybe better to try the safest way.
any comments/suggestion is greatly appreciated (but I think I've made up my mind already).
This is what I've found out so far:
PRO Self Leveling compound:
1) the smooth surface helps using notched trowels so tiling should be easier
2) acts as a protective barrier while tiling - eg. one can walk on it while while extra care would be needed when walking directly onto the ufh mat (in fact it should be avoided altogether).
3) it should help on the long term - e.g. if a tile need to be replaced, the extra layer of SLC should provide an horizontal key for the chisel and the cable are better protected.
4) air pockets are less of an issue with SLC as is more penetrating than adhesive - so the cable are more efficient.
5) easier to rectify tiling mistakes on the spot (while tiling) - if I discover that a tile isn't level later on it can be removed without damaging the cables....
Against SLC:
1) the extra layer of SLC mean a thicker layer of mass between the heating cable and the tile(at least 5mm for SLC and 3mm for adhesive = 8mm) - this way the heat has to travel more to reach the tile so it would take longer....I guess without SLC it is possible to lay 5mm thick adhesive (the heating cable are 3mm thick).
2) extra building costs - - fortunately the area in question is relatively small (2.7 square metres) so only 1 bag of SLC is required (£15 extra).
3) extra work - there is an extra stage to be added (though this might be compensate by the fact that tiling is easier when SLC is used).
Right now, I'm thinking of using SLC - point 4 and 3 of the PRO section above are very relevant in the long term...beside, this is my first UFH and tiling project so it's maybe better to try the safest way.
any comments/suggestion is greatly appreciated (but I think I've made up my mind already).
