- Reaction score
- 26
Defo expansion gap needed but also with any underfloor heating you need a solid bed of adhesive. One reason for needing a solid bed is for thermal transfer of heat up from the mat and through into the tile. Air is a very poor conductor of heat and so if you have air trapped between trowel ridges you have a very uneconomical system. Secondly, if the air pockets are quite large you can also have a problem where the heated air expands and again, it could possibly cause lifting of the tiles, especially if they weren't very well bedded to start with.
When solid bedding it's always better to butter the back of the tile.
When solid bedding it's always better to butter the back of the tile.