conservatory floor screed question

30 May 2005
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United Kingdom

I am ready to lay a floor screed on top of underfloor heating pipes which is to be 75mm thick - a bit confused (re mixture) becuase i have searched the forum and some posts say that you should be able to roll a ball of the screed and it should retain its shape but have seen other pictures where the mix is really runny to get round the pipes (the heating instructions suggest a screed additive). Any advice would be grateful esp regarding finishing - I had this vision of pouring the mix over the floor and it self levelling with a minimum of finishing???? I am finishing the floor with laminate tile effect.

Many thanks
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floor screed mix should only have just enough water mixed to it so that when squeezed it just holds together.

this is so that you don't encourage any water to the surface whilst floating the floor.

water on the surface causes "dusting". this is a no no.
I'm about to do the same..... I've wondered about this myself and asked the underfloor hearing guy. The mix I've been told is 4:1 concreting sand to cement, but that is the sum total of the advise.

I've been told by a couple of people that its almost a dry mix - which I wasn't comfortable with.

Noseall... its difficult to tell what you mean on via text only. just holds together is kinda damp rather than wet and definitely no sloppy? Should I be using any plastisiser?
definitely no plasticiser.
you compact the dryish mix with the trowel and plastic float.
the important thing is keeping the mix constant.
a dryer mix will compact and ultimately sink, more so than a wetter mix. which is more dense.
this will lead to an un even floor.
in other words keep the mix entirely dry.
at least you know how each mix will behave.
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iturner1 - can you post when you have done it and let me know how you got on! - I have just laid the pipes for the heating and am about to pressure test them for a few days before starting

If it's like the PolyPipe system remember you need to have it pressurised while thye floor is drying. I ran mine at 60 psi and used a dry mix of screed followed by a resin based sealer / self leveler and it's been fine.

Regards - J
I will, but its looking like three weekends aways. It is indeed polypipe, and the pipes are laid. I'm now waiting for the manifold to be connected up so that we can run the water test and then pressurise reader for the screeding. I've decided to pay someone to do the screeding as at the minute I haven't got the time.
I Turner. I also live in Manchester- who did you get to do your floor screeding, as I am just about to do it and am struggling to find a local company that will deliver/pump in
but a tip would be talk to a local tile shop as they often have people they can recommend for either delivering screed or doing it all for you.

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