liquid screed vs. concrete for underfloor

FergusD

I'm putting in underfloor and am getting conflicting stories on screeds. My engineer tells me that liquid screeds are too expensive for what they will give us, but some UFH suppliers are really pushing them - any views?

We have space and a guy who'll do the concrete version cheaply.

Thanks,

Fergus.

Western_sean

We have about 75mm concrete with UFH and it's proved fine (I think this winter was a good test of a heating system!).

Liquid screeds tend to be poured thinner which I think has drawbacks in terms of available thermal mass - I'm sure someone else will be more qualified to comment on that.

Good luck with the build
Sean

FergusD

Yeah, I gather it's a double edged sword - it's less thermal mass, but that equates to a faster response time. Any one any thoughts on it? Which are most people using? Does it make any practical difference if the controls are good on the system?

Thanks,

Fergus.

soldsold

75mm concrete floor should be more than enough thermal mass

FergusD

The non-concrete screed has less thermal mass, thus presumably faster heat up and cool down times. Is this of benefit in reality or is it just extra expense?

Thanks,

Fergus.

soldsold

If your house is very well insulated, airtight and has dense insulation such as pumped cellulose to even out the daily temperature swings (ie thermal inertia/ decrement delay) then it stands to reason that the fast heating and cooling of your underfloor system is less important.

If insulated to building regs or "a bit better" than the regs, the lower thermal mass of a liquid screed will work in your favour to react quicker to temperature fluctuations.

Dont forget the cost of mesh, labour, rent of powerfloat, tilers levelling compound when comparing prices.

In my case I just got a good screed/ powerfloat guy and kept the money for other stuff, but Im using radiators so might have looked at it differently if using UFH

mr_edge_to_you

Our builder put in a concrete floor. In fairness to him he doesn't cut corners and i'm sure if he felt there was a better product on the market at that price he'd use it. It is a very good job and we are happy with the result.

coffeyd

Building new home June 2020, sealed house, underfloor heating ground & 1st floor, any thoughts on standard concrete 75mm or expensive screed circa 40mm or DIY webber screed. ?

Count Mondego

There's advantages and disadvantages to both. I priced both a 50mm Sudanit 280 Alpha Hemihydrate screed (quick to react) and a 75mm liquid cement screed.

My problem with the 50mm was that my subfloor was a bit off in places and he'd have to put 60-70mm on to make sure all UFH was covered enough. This priced it out of it. The liquid cement was close to half the price as a result and I'm very happy with it.