Concrete Screed for wet UFH - advice please

[oranjeboom]

Well the inspector always knows best....   But why? Greater threat of movement if the founds are different?

 

Yes, I'd be reluctant to fill all that in with MOT too. May as well get additional insulation in and depending on what u-value you are aiming for, you could save a bit by going for 160 PIR/ 100 EPS (0.085 W/m²K)

[joth]

3 minutes ago, oranjeboom said:

Well the inspector always knows best....   But why? Greater threat of movement if the founds are different?

 

Indeed. nothing specific was spotted in the ground to suggest it, but just cited the theoretical risk of drift. The compounding factor is the original SE that signed off the design has since retired (ill health) and the next SE consulted agreed with the inspector, which left us rather high and dry.

 

6 minutes ago, oranjeboom said:

May as well get additional insulation in and depending on what u-value you are aiming for, you could save a bit by going for 160 PIR/ 100 EPS (0.085 W/m²K)

 

Interesting idea. The previous plan was 0.127W/m2K everywhere which is already good  enough for EnerPHit+ anyway...

 

[Big Jimbo]

What annoys me is that the cost of say 100mm pir against 50mm. The 100mm should be twice the cost of 50mm, but it never is. I have used Two lots of 100mm in the past. Not because it was needed, but because i resented being asked to pay 3/4 of the price of 100mm for 50mm.

[Homer92]

Some excellent reading in this thread!

I'm having 150mm PIR, and 75mm sand /cement screed with my UFH, my question is how do I protect the UFH pipes when wheeling in the screed? And indeed the DPM and PIR boards?

A ground floor of nearly 200m2 that's a lot of wheeling!

[Declan52]

You don't. It's usually pumped in even a sand cement screed. If they don't own a pump a wheel barrow wouldn't damage it anyway.

[Russell griffiths]

We just wheelbarrowed in 26 tonnes of screed similar size to yours. 

You don’t need to protect the dpm as that’s under the insulation. 

To protect the pipes you will need a few sheets of chipboard flooring and lay it on top of pipes, you will need a person in charge of moving the boards or the screeners will just ignore them. 

Or as Declan said get a screed pump. 

The lads that did mine have a pump but still prefer to barrow as they reckon the time they set up the pump they would have got one room done. 

5 lads laid 180m in a day by 3pm. 

[Homer92]

Ok thanks I wasn't sure you if you could pump screed. But I'm pretty sure the screeders talked about wheeling it when quoting, I'll get a few sheets of ply down.

I thought there is a polythene layer on top of the PIR and under the UFH pipes. Don't want to tear it.

[Mr Punter]

13 minutes ago, Homer92 said:

I thought there is a polythene layer on top of the PIR and under the UFH pipes. Don't want to tear it.

 

The polythene is mostly only there to stop screed getting in between board joints.  Traditional screed is fairly dry, needs to be barrowed in and is 75-100mm thick.  Quite an art to laying it and fairly labour intensive.  The liquid screeds (gypsum or cement based) are pumped in and normally 40-70mm thick.