Can I do 50mm screed?

[mgx]

Hi, I am renovating a flat, floor is concrete slab on ground, over which there is 70mm screed - we are removing 70mm screed (and all the service pipes within it) and re-laying with 20mm insulation (and new water plus elec service pipes) and wet UFH clipped in this then rescreeding. I'm sensitive to the floor height, and if possible, would like to rescreed on the UFH at 50mm (instead of 65mm as usually recommended). Is there a safe way to do this? I read that liquid screed can do 50mm, but that's not practical (cost wise, for such a small area - 50sqm), is there a way I can achieve it with normal sand/cement screed - say if I put reinforcing bars in above the UFH or some strengthening compound? We will have 18mm timber flooring over the screed btw. Or should I just wear the extra 15mm and go for recommend 65mm screed. Any help much appreciated!

 

[noseall]

50mm with fibres will probably be ok, but it is a chance decision, as the ufh may have an effect.

Your floor your choice.

 

[mgx]

Thanks, I am not into chance decisions - only if there is a no (or negligible) risk solution that can be used. I think I will just go for 65mm, the main downside is that it will create a small step at the door into common area of the building.

 

[alfiembra]

50mm screeds always used to be the norm on concrete slabs with a 1:3 cment sand mix, but with the addition of UFH I guess your concern is cracking. There are lots of admixtures available nowadays, epoxy's etc. that may be the answer to your problem get in touch with a specialist company like Fosroc for example and see if they can recommend an additive to the basic mix.

HTH

Alan