Basement Internal Insulation

[steveb21]

Basement build with specialist infilled concrete blocks - 325mm wide, filled with rebar and C35 concrete.

Basement is 2/3 in ground, 1/3 above ground.

Internal wall and floor has been tanked using KA tanking slurry.

No external insulation - this was not possible due to space restrictions.

 

What is suggestion for wall insulation?

 

I was planning to:

>> 50mm XPS Foam glued directly to basement walls > 50mm Expanded Polystyrene EPS70 Insulation Board 2400mm x 1200mm (8′ x 4′) | Insulation Wholesale

 

>> 50mm Metal stud in front, attached floor to ceiling > Metal C Stud Partition - 10 Pack | Steel Framing - Fast Build (fastbuildsupplies.co.uk) and MF Ceilings - Suspended Drop Ceiling Systems - Fast Build (fastbuildsupplies.co.uk)

 

>> Metal stud filled with insulation mineral batts (these would fit nice and snug in between the metal studs)

 

>> Vapour Control Layer

 

>> Plasterboard

 

>> Skim

 

 

Thoughts please?

 

[Conor]

Firstly, what will the basement be used for, and will it be heated? 

100mm of XPS / mineral wool is not nearly enough, you want a min of 100mm PIR. 

[steveb21]

The basement will be a living space.  

Bar, sofa, tv, office.

 

It will be heated. 

Floor slab has 100mm of rigid insulation.  There will be UFH at 150mm spacing with screed.

 

I dont think keeping heat in will be much of a issue, over the winter it was surprisingly not that cold down there.  Trying to keep an eye on moisture control.... will have trickle vents in 3 windows, couple of extractor fans and if needed a dehumidifier.

 

Other option I proposed was

Metal stud (50mm) installed slightly off the wall - floor to ceiling

Metal stud filled with insulation wool bat (50mm)

Vapour Control Layer

37.5mm insulated plasterboard (25mm insulation board, 12.5mm plasterboard)

Skim

 

 I am not sure about using the insulation batts so close to the walls though.  

 

Edited March 31, 2023 by steveb21

[Pocster]

How large is it ? Just wondering how much space you lose to insulating internally … ( appreciate you have to though ) . 

[Mr Punter]

If this is a new build you will need a lot more wall insulation.  Also, the tanking slurry may well not keep it dry and does not seem to be for habitable basement space.

[steveb21]

Its been tanked for a while and has been dry.  Approx. 6 months.

 

Area size is 9x6m - so just over 50m2.

 

 

[saveasteading]

1 hour ago, steveb21 said:

specialist infilled concrete blocks

What blocks are these? I did a deep basement using special concrete blocks that joggled about for interlock. But we still had to use a very expensive waterproofing layer outside it and under the floor. 

I'm nervous about yours. Is it fully designed, and can you tell us more?

 

Re insulation, I would be happy with the floor, as the earth will come to some steady temperature, being a long way from cold weather.  I think this is undervalued in theoretical calculations. So on the walls I would want PIR for maximum effect. 100mm again perhaps, (still getting some benefit from being away from the weather) then vcl/ stud/ 25mm service void then 1 layer plasterboard.

All assuming it stays dry.

 

 

 

 

[steveb21]

Blocks > Stepoc | Structural Products | Anderton Concrete

 

I really dont want to push more than 115mm.

 

"100mm PIR/ vcl/ stud/ 25mm service void then 1 layer plasterboard."

Above would take me nearly to just under 200mm.  Really do not want to lose that much space.

 

 

Would 100mm PIR glued against the walls

VCL

Plasterboard > fixed onto the PIR

Skim

 

What the glue hold things up? I am not planning on attaching anything heavy to the walls.

I will have to run service/electrical points via cut outs on the PIR.

Edited March 31, 2023 by steveb21