Y
ythan
I think a key problem is the fact that UFH mesh has been laid upside down.....
The mesh is then floating ontop of the heating wires (red in the photo)) thereby preventing the adhesive from being properly towelled down (through the mesh) onto the substrate. The imprint of the sticky tape on top of the (upside down) webbing can be seen on the back of the tiles....
The other problem is probably incorrect and insufficient thorough mixing of the adhesive, the use of it while it's not still fresh, and poor towelling technique ie failure to achieve to get a good adhesive bed. Finally not bedding each tile down properly. I've not found buttering of tiles to be necessary.....though i've only used porcelain tiles. The central heating pipes under the floor may have also caused the adhesive to dry off preventing proper bedding in.
I would doubt if there is any problem with the primer supplied with the UFH. Actually, I would always use thermal insulation boards on top of the substrate as the extra cost of these is soon repaid by the energy savings. Also I've only used BAL single part fastflex with UHF, and take great care when trowelling not to damage the heating wires.
One last point is that if the substrate had have been chipboard then the chipboard would have unfairly got all the blame! and other problems may have been missed. I've had no problems tiling on chipboard floors, but within the forum, i've noted that chipboard seems to get blamed for all tiling problems, and encourages, i think, unnecessary complication, and cost, of using ply overlay, backer boards, decoupling membranes ditra etc.
I'd suggest you start again, get the UFH tested to see if it can be re-used, get thermal boards, and BAL single part fastflex, take extra care with mixing and applying the adhesive, and bedding in the tiles.
good luck
The mesh is then floating ontop of the heating wires (red in the photo)) thereby preventing the adhesive from being properly towelled down (through the mesh) onto the substrate. The imprint of the sticky tape on top of the (upside down) webbing can be seen on the back of the tiles....
The other problem is probably incorrect and insufficient thorough mixing of the adhesive, the use of it while it's not still fresh, and poor towelling technique ie failure to achieve to get a good adhesive bed. Finally not bedding each tile down properly. I've not found buttering of tiles to be necessary.....though i've only used porcelain tiles. The central heating pipes under the floor may have also caused the adhesive to dry off preventing proper bedding in.
I would doubt if there is any problem with the primer supplied with the UFH. Actually, I would always use thermal insulation boards on top of the substrate as the extra cost of these is soon repaid by the energy savings. Also I've only used BAL single part fastflex with UHF, and take great care when trowelling not to damage the heating wires.
One last point is that if the substrate had have been chipboard then the chipboard would have unfairly got all the blame! and other problems may have been missed. I've had no problems tiling on chipboard floors, but within the forum, i've noted that chipboard seems to get blamed for all tiling problems, and encourages, i think, unnecessary complication, and cost, of using ply overlay, backer boards, decoupling membranes ditra etc.
I'd suggest you start again, get the UFH tested to see if it can be re-used, get thermal boards, and BAL single part fastflex, take extra care with mixing and applying the adhesive, and bedding in the tiles.
good luck
