Jilly Posted March 25, 2020 Posted March 25, 2020 Hi, I am just having the Building Regs drawings for my stable conversion and need your suggestions, please, as we have a bit of a dilemma because I want hippy, non off gassing stuff! I need something relatively thin with a high compressive strength. Due to restricted head height, we ideally have only 70mm, but we might be able to use a little more. The p/a value is 0/566 (perimeter/area) The architect has quite reasonably suggested Celotex as a cost efficient solution.
PeterW Posted March 25, 2020 Posted March 25, 2020 What is the full floor make up ..? Is that 70mm insulation with 100mm concrete / screed over ..?? Under floor heating ..?? Need to know that to comment.
Jilly Posted March 25, 2020 Author Posted March 25, 2020 Sorry, 150mm concrete slab with a painted on DPM or tanking. Th structural engineer has suggested a suspended floor. I don't want to underpin, and it seems screed and UFH will be too heavy.
PeterW Posted March 25, 2020 Posted March 25, 2020 So that’s 150mm on top of insulation ..?? Are there any walls built on top of it ..?? Structural walls not stud or non structural That is massively over spec for a ground bearing slab. Section drawing would be helpful.
A_L Posted March 25, 2020 Posted March 25, 2020 On 25/03/2020 at 11:11, Jilly said: The p/a value is 0/566 (perimeter/area) Expand Obvious typo, can you give actual exposed perimeter and floor area. What is your target U-value (building regs for England?).
Jilly Posted March 25, 2020 Author Posted March 25, 2020 Sorry, the existing floor is a concrete slab, 150mm thick. The floor will go on top. The minimum u value we could have is 0.28 (the 70mm Celotex would be be 0.22, so that would be my target). The p/a value is correct. The building is just under 60m2. Ie 10+10+6+6/10 x 6 = 0.533 The 0.566 calc comes from the exact figures the architect has.
A_L Posted March 25, 2020 Posted March 25, 2020 At 70mm the maximum thermal conductivity needed is about 0.024W/m.K so no realistic alternative. EPS300, thermal conductivity 0.033W/m.K would have to be at least 100mm to get 0.28W/m2.K The 150mm slab will spread any wall load to a considerable degree, wether sufficiently will depend on exact construction details 1
scottishjohn Posted March 25, 2020 Posted March 25, 2020 On 25/03/2020 at 11:11, Jilly said: I want hippy, non off gassing stuff! Expand foam glas chips -- between joists www.dreieck.co.uk £85 cubic m bag 1
PeterW Posted March 25, 2020 Posted March 25, 2020 On 25/03/2020 at 14:01, Jilly said: Sorry, the existing floor is a concrete slab, 150mm thick. The floor will go on top. Expand What floor do you mean going on top..??
Jilly Posted March 25, 2020 Author Posted March 25, 2020 (edited) The insulation and floor will go over the old concrete stable floor. Edited March 25, 2020 by Jilly
Conor Posted March 25, 2020 Posted March 25, 2020 Take a look at insulating screeds. You could put down 70mm PIR then insulating screeds on top to give you your floor ready to finish.
scottishjohn Posted March 25, 2020 Posted March 25, 2020 On 25/03/2020 at 16:30, Conor said: Take a look at insulating screeds. You could put down 70mm PIR then insulating screeds on top to give you your floor ready to finish. Expand the first post said there should be no off gassing --thats limits choices
PeterW Posted March 25, 2020 Posted March 25, 2020 On 25/03/2020 at 16:22, Jilly said: The insulation and floor will go over the old concrete stable floor. Expand @Jilly what is the top floor surface ..? What are you putting over the insulation...??
Jilly Posted March 26, 2020 Author Posted March 26, 2020 Haven't chosen it yet, but thinking about wood
A_L Posted March 26, 2020 Posted March 26, 2020 What is the distance from the top of the original floor to the top of the new floor surface and how flat is the original floor?
PeterW Posted March 26, 2020 Posted March 26, 2020 Ok so @Jilly if you are saying you are putting a floating floor over the insulation which sits on the 150mm concrete then you have an issue. You’ll need to use min 90mm PIR and then float a 22mm chipboard floor that is then fitted with your final floor finish. That assumes that the current floor is dead flat, and if not you will need to use levelling compound on the slab to start with. You don’t need a liquid DPM - you can put that on top of the insulation and below the chipboard and use standard DPM with the excess taped up the walls. 1
Jilly Posted March 26, 2020 Author Posted March 26, 2020 Due to a restricted head height, we only have 100mm from the existing concrete floor to the top of the new floor. The concrete is levelish, but its under a lot of rubber stable mats so I can't inspect it fully at the moment. (next job).
PeterW Posted March 26, 2020 Posted March 26, 2020 @Jilly With 100mm build up, what does that leave your floor to ceiling height ..?
PeterW Posted March 27, 2020 Posted March 27, 2020 Ok so I would seriously consider digging out the floor. It will be better in the long term and £2-3K spent now will pay dividends long term. 1
Simplysimon Posted March 27, 2020 Posted March 27, 2020 On 27/03/2020 at 20:37, PeterW said: Ok so I would seriously consider digging out the floor. It will be better in the long term and £2-3K spent now will pay dividends long term. Expand +1 to above, have you tried standing in a room with a 2.1m head height? with digging out you get to put in 200mm insulation plus screed and ufh and have more headroom 1
Jilly Posted March 28, 2020 Author Posted March 28, 2020 We have explored this with the structural engineer and digging the floor out will compromise the foundations, meaning that we need to underpin: quotes for this have varied from £15-30K, so not an inconsiderable difference. We are compromising by taking part of the roof off to create a vaulted ceiling over the living room (I would rather spend money where I can see it!, with the lower ceilings over the kitchen part/bedroom and bathroom. Demolition is a non starter unless we do it 'accidentally' and I'm too risk averse for that. It's looking like Celotex it is! The other options are just too thick.
PeterW Posted March 28, 2020 Posted March 28, 2020 If you want ultra thin then look at Vacuum Insulated Panels or Aerogel. Both can do what you want at significantly thinner layers but at a much higher price. And is the SEng saying the floor is holding the walls up ..? Or that you can’t excavate down within a certain area ..? You could have the floor cut out say 300mm from the edge and drop the centre sections - again, not that cheap but not hugely expensive. £15-30k for underpinning a single storey building sounds a lot. How much wall is that..? Have you had quotes from anyone such as Geobear who do the injected resin systems .?
Simplysimon Posted March 28, 2020 Posted March 28, 2020 On 28/03/2020 at 10:44, Jilly said: (I would rather spend money where I can see it!, Expand and unfortunately, there is your problem.
Russell griffiths Posted March 28, 2020 Posted March 28, 2020 @Jilly tbh you should spend your money on the bits you cannot see, they are the important bits i do believe you have a limited budget, but better to get a good structure and fill it with second hand furniture than a compromised structure that you cannot improve in the future when you realise it’s not come out as good as you wanted. Are you allowed to lift the wall plate up , thus lifting the roof. 2.1 will be a major compromise, I would apply to lift the roof up by 300mm.
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