David Mclean Posted February 2, 2021 Share Posted February 2, 2021 Hello I have had underfloor heating put into a house, anhydrite screed was used. Screed sat for about 5 months before system was commissioned, was warmed progressively over a number of weeks and by the book. We now have three cracks in the hallway were we want to tile. The company that installed it say its not a problem just glue it..... and tile over it not a problem. Can anyone offer some advice on this? can I tile over these cracks? can I glue it? Link to comment Share on other sites More sharing options...
epsilonGreedy Posted February 2, 2021 Share Posted February 2, 2021 Just the door threshold? These are a typical weak point. Link to comment Share on other sites More sharing options...
gc100 Posted February 2, 2021 Share Posted February 2, 2021 I think its pretty normal to get a few cracks. We have the same type of floor and we have 2 or 3 of these. You need to make sure you use a separation membrane between floor and tiles. We used DITRA mating. My house just got flooded 2 days before we where meant to move in . We've had the UFH on max 24/7 trying to dry the floors out where we did not have tiles and the floor has got pretty hot - so far - touch wood - we've not had any cracks in the tiles, so the matting it working thus far. Link to comment Share on other sites More sharing options...
Temp Posted February 2, 2021 Share Posted February 2, 2021 Same happened to me. I've posted about it a few times on this forum. Again in the past week or so. What happens is two areas of screed (one in each room) meet at the doorway. They dry and shrink ever so slightly towards their own centres forming a crack. Ours happened after laying the stone floor and cracked the stone. The only way to prevent a problem is to form a deliberate crack (aka expansion gap) at the doorway to ensure its straight. Too late for that now. If you want to tile over it I would recommend using some form of decoupling mat between the screed and tile. With anhydrite screed you also have to be careful about laitance... https://www.bal-adhesives.com/tiling-onto-calcium-sulfate-anhydrite-screeds/ Link to comment Share on other sites More sharing options...
gc100 Posted February 2, 2021 Share Posted February 2, 2021 Yes for large tiling areas or thresholds you need expansion strips - forgot to mention! Link to comment Share on other sites More sharing options...
nod Posted February 2, 2021 Share Posted February 2, 2021 It isn’t a problem But you must have an expansion joint in every doorway if you are tiling mans matting under the tiles 3 Link to comment Share on other sites More sharing options...
Pocster Posted February 2, 2021 Share Posted February 2, 2021 I had exactly the same ! use decoupling mat flexible adhesive flexible grout expansion strips in doorways ? 2 Link to comment Share on other sites More sharing options...
Noddy2021 Posted February 4, 2021 Share Posted February 4, 2021 This happened to my screed - around the doors, etc. I was told it was normal and we went ahead with glued wooden flooring. Everything seems fine. 1 Link to comment Share on other sites More sharing options...
DragsterDriver Posted March 28, 2022 Share Posted March 28, 2022 On 02/02/2021 at 15:08, nod said: It isn’t a problem But you must have an expansion joint in every doorway if you are tiling mans matting under the tiles i have these- do you cut the strip right out or trim it flush? Link to comment Share on other sites More sharing options...
Temp Posted March 29, 2022 Share Posted March 29, 2022 I would just trim it flush. 1 Link to comment Share on other sites More sharing options...
DragsterDriver Posted March 29, 2022 Share Posted March 29, 2022 Never had cracking before but have a couple this time Link to comment Share on other sites More sharing options...
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