In message anCbc.163$4Y4.8@newsfe1-win, Steve House
writes
Does 4:1 sharp sand : portland cement with a plasticiser such as liquid
Febmix sound about right?

"Steve House" wrote in message
...
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?


We use 10 parts quarry dust, 2 parts plastering sand, 3 parts cement.
Mix with water gauged with mortar plasticiser so that squeezing the mix
hard in your fist hardly produces a drop of water.
If the mix is being hand screeded put it down in layers so that you can
compact the mix around the pipes and ensure that there are no voids.
Machine screeding is *much* easier and quicker.
Finish off the last layer by tamping and screeding. 3 to 4 hours later
you can walk on the mix to float it off with a wooden (plastic) float.
This should be fine for ceramic or quarry tiles once it has cured (could
take 12 weeks). Be patient.
For a smooth finish polish with a steel trowel.
Power float is *much* easier and quicker.
Lay down a plastic sheet to retard setting.

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