Please can you check Newbies Ground floor construction?

[Warrentdo]

Hello, I could really do with some advice.

Plans don't give the detail and I'm trying to get into the detail as im doing this myself.

Extension is being built with one corner having 2 existing walls and other opposite corner two new walls making a rectangle. 

Does the following build up look ok?

 

Floor 0.18 w/m2k
Liquid screed 55mm - 75mm liquid screed (im looking for help on type). 25mm perimeter insulation on this section only.
UFH
Vapour Barrier 500 gauge / 125mu Polythene sheet. To overlap Liquid screed vertically?
Insulation 100mm Kingspan K103 100mm 0.019 W/mK (taped joints) or
Celotex XR4000 / GA4000 0.022 W/mK (taped joints)
DPM 1200 gauge / 300mu (0.3mm) polyethylene sheet. overlap all DPM vertically?
Concrete C20 150mm.
DPM 1200 gauge / 300mu (0.3mm) polyethylene sheet. laid above DPC in new walls. How do I tie into DPC in existing walls? chase in or bond?
Sharp Sand 25-50mm?
MOT Type 1  150mm min (or what ever required to meet FFL).

 

Thank you for taking the time to look and help a newbie.

Also sorry if I have posted in the wrong section.

 

Regards

 

warren.

 

 

Edited October 20, 2022 by Warrentdo

[Dave Jones]

too many dpc's.

 

you need one under the insulation on top of the sand blinding(EPS is much cheaper than celotex, pointless taping joints) that laps up onto the DPC the brickies should have left hanging out the wall all the way round.

 

a

[Warrentdo]

28 minutes ago, Dave Jones said:

too many dpc's.

 

you need one under the insulation on top of the sand blinding(EPS is much cheaper than celotex, pointless taping joints) that laps up onto the DPC the brickies should have left hanging out the wall all the way round.

 

a

Hello Dave, thanks for the info. The concrete is on top of the sand bindings, insulation then on top of conc. I was worried with EPS of point loading due to thinner screed. New walls not built yet so thought lapping DPM over top of DPC then wall on top. not sure what to do on existing wall.

Edited October 20, 2022 by Warrentdo

[JohnMo]

43 minutes ago, Warrentdo said:

Vapour Barrier 500 gauge / 125mu Polythene sheet

This sheet isn't a dpc, it there to stop hydrogen bubbles forming from the reaction between aluminium foil on the insulation and the concrete in the screed.

[JohnMo]

If you can get more insulation in the floor with UFH I would, this will help limit downwards heat loss.

[Warrentdo]

10 minutes ago, JohnMo said:

This sheet isn't a dpc, it there to stop hydrogen bubbles forming from the reaction between aluminium foil on the insulation and the concrete in the screed.

I agree, not DPC but vapour barrier and to stop screed finding its way under the insulation as well?

[Chanmenie]

I’ve just finished my ground bearing slab

from bottom up
100mm crushed concrete compacted

23/30 mm fill sand blinding

1200g DPM membrane

200mm Celotex XR4000 two layers of 100mm all joints staggered and taped 

slip membrane 

UFH pipes 

100mm fibre reinforced concrete  ecFlow 

 

why have concrete and screed ? That’s two floors you only need one

[Warrentdo]

1 minute ago, Chanmenie said:

I’ve just finished my ground bearing slab

from bottom up
100mm crushed concrete compacted

23/30 mm fill sand blinding

1200g DPM membrane

200mm Celotex XR4000 two layers of 100mm all joints staggered and taped 

slip membrane 

UFH pipes 

100mm fibre reinforced concrete  ecFlow 

 

why have concrete and screed ? That’s two floors you only need one

its what's spec'd on the drawing, but I can challenge. I was thinking of a  top thinner screed so that it heats up faster?

[Dave Jones]

if the walls not built, use block and beam and avoid the hassle completely.

[Chanmenie]

10 minutes ago, Dave Jones said:

if the walls not built, use block and beam and avoid the hassle completely.

Why use block ad beam it’s expensive and less thermally efficient 

[JohnMo]

19 minutes ago, Chanmenie said:

I’ve just finished my ground bearing slab

from bottom up
100mm crushed concrete compacted

23/30 mm fill sand blinding

1200g DPM membrane

200mm Celotex XR4000 two layers of 100mm all joints staggered and taped 

slip membrane 

UFH pipes 

100mm fibre reinforced concrete

Almost the same as mine, but I have a further 150mm reinforced concrete below, and strip foundation below that.  Due to being at top of a historical sand dune.

[Chanmenie]

19 minutes ago, Warrentdo said:

its what's spec'd on the drawing, but I can challenge. I was thinking of a  top thinner screed so that it heats up faster?

Why do you want it to heat up faster ? 
it will cool down faster 

a nice thick concrete slab works like a big storage heater and evens out the temperature fluctuations. 

Edited October 20, 2022 by Chanmenie

[Chanmenie]

Just now, JohnMo said:

Almost the same as mine, but I have a further 150mm reinforced concrete below, and strip foundation below that.  Due to being at top of a historical sand dune.

Yeah I have strip footings at 700mm 

but my ground was lovely firm sand and gravel 

[Warrentdo]

16 minutes ago, Dave Jones said:

if the walls not built, use block and beam and avoid the hassle completely.

Sorry although I mentioned walls not built, they are built to DPC. Wish I thought of block and beam before!

[JohnMo]

Ignoring any solar gains, our house sits at a steady 19 degrees.  Have a big gas boiler and even bigger buffer, to keep the boiler happy.  Flow temp in the floor is 23-26 depending outside temp.  192m2 operating on a single zone.

[JohnMo]

Not sure I would change, even if I had the choice.  Steady temperature below the floor, about 8 degs, instead of a breeze at what ever temperature it is outside, could be -5, so heat loss could be bigger.

[Chanmenie]

33 minutes ago, Warrentdo said:

Sorry although I mentioned walls not built, they are built to DPC. Wish I thought of block and beam before!

If you are able to do ground bearing slab then forget block and beam 

[Dave Jones]

14 hours ago, Chanmenie said:

Why use block ad beam it’s expensive and less thermally efficient 

silly.

[Chanmenie]

10 hours ago, Dave Jones said:

silly.

You care to justify that comment ? 

[Warrentdo]

Hello Guys, moving on with this.

Insulation, for the same price

100mm Kingspan K103  0.019 W/mK or
150mm Celotex XR4000 0.022 W/mK 150 for the same money but lower W/mK

150mm Eco Versal 0.022 W/mK 150 for the same money but lower W/mK higher crush strength.

 

Warren.

Edited October 23, 2022 by Warrentdo

[Chanmenie]

20 minutes ago, Warrentdo said:

Hello Guys, moving on with this.

Insulation, for the same price

100mm Kingspan K103  0.019 W/mK or
150mm Celotex XR4000 0.022 W/mK 150 for the same money but lower W/mK

 

it also looks like you can use Celotex XR4000 for everything roof, wall and floor

 

Warren.

I used the XR4000 

hopefully someone more knowledgeable will be along to explain if 150mm @ 0.022 W/mk is better than 100mm @ 0.019 W/mk

I’m guessing it is but hopefully someone will confirm.

 

I went with 200mm in 2 layers of 100mm to aim for a 0.11 U value