Hi Folks,

 

I am tiling on a 75mm screed with underfloor heating from an ASHP. I have large windows in my kitchen / sitting / diner (high solar gain). My tiler is going to use a decoupling mat, and tells me that he has never had a problem when using decoupling mats, and that expansion joints are not required. 
 

Do you think expansion joints are needed as well as decoupling mats? Or is that overkill?
 

thanks

 

 

Arenite
 

 

There’s a big difference between expansion joint and a movement joint. 
what sort of area are you talking about, I have probably 50-60 m in one area with no expansion joints, but I do have 3-4 movement joints where the large area joins thin smaller areas. 
I was always told that was the place cracks would occur. 
imagine the shape of a tennis racket, it will always crack where the head joins the handle. 
I also have movement joints in every doorway. 

Russell,

 

the biggest room is 11 metres long, by 6 metres wide. 

Watch out at doors between rooms. Should have movement/expansion joints there. Each area of screed can shrink towards it's own centre cracking where the meet. Has happened to us.