Nick Brooks wrote:

Steve House wrote:

Hi,

I am looking to install underfloor heating in a new build conservatory. I
will be using 50mm Celotex insulation and UFH pipes attached to a steel
mesh. I will be getting a local tradesman in to do the 75mm screed.

I have seen various UFH information that talks about using an additive in
the screed. What screed mix should I be looking for i.e. sand/cement/grit
ratios and what type/where can I get the right additive for this
application?

Cheers

Steve..


Unless you need the wire mesh for structural reason it's MUCH easier to
use the red plastic stuff illustrated here

http://www.polypipe.com/POLYPIPE/pp_..._02-01-03.html

the pipes just clip in

Nick Brooks

Well, I did need the steel for structural reasons, and it took about
half a day to tie wrap the pipes to it. Loosely.

No special additive needed in the screed.

The plastic trays were a LOT more expensive than a day of my time to do
about 150 sq meters of floor. Even if you inlcuded the cost of the steel.

The only thing worth saying is that teh csreed was mixed in a cement
mixer, and teh variability from the oafs that mixed it caused some
problems. If its a big area, get a contractor in and readymix. ISTR it
was about 5:1 sand to cement and a pretty dry mix.

I did get some cracks where the job was not completed in a single day -
but I poured a lot of sligthtly diluted PVA down the cracks and in time
it set, shrank, and pulled it all back to one solid lump. Good trick.

In practivce it woorks superbly - UF and sreed. I did need to do a fair
bit of levelling afterwards tho. Screeders can seldom achieve the
necessary accuracy in the speed required.