Garage conversion, wall insulation

[garydc]

We're currently doing a garage conversion, its 103mm single skin walls with centre piers. Detached from house, and relatively small, so a P/A value of 1.

We've entirely blackjacked the walls and floor, laid a DPM, built a 3"x2" timber stud wall at 600mm centres and noggins, with 50mm Celotex cut in between the timber.

My question is does this pass building regs. I've got them round and called them trying to get some sense out of them, each time they've said 50mm will 'probably' be okay, and not committed themselves to a definite yes or no. Last time they came round, they were rude, saying we are not here to help you, and said they won't come back until its all complete, nor should I phone them for any advice!

So obviously concerned as I'm now in a position where I'm ready to buy plasterboard.

Any ideas please?

 

[mikric]

I would say crack on mate.
Feel sorry for you,your BCO sounds like a complete tosser to me

 

[freddiemercurystwin]

I would say crack on mate.
Feel sorry for you,your BCO sounds like a complete t****r to me

Well it gets you to 0.31 mikric so it doesn't really comply does it? But the OP's BCO does sound like a t****r though.

 

[garydc]

Oh dear, that doesn't sound too good.

I'm also rendering the outside walls, and inside using foil backed Gyproc Wallboard Duplex over the studs, then plastering. Does that bring me within the 0.28 suggested value. Should also point out that the 2 external walls have an additional skin of engineering bricks on the outside, running nearly halfway up the wall. The other wall is joined to the neighbours garage wall, not a party wall.

Or if still not within 0.28, guess I'm looking at using something like Thermaline plasterboard. Even still wouldnt have a clue how thick

 

[freddiemercurystwin]

Well I wouldn't worry too much but 60mm will get you there with ease. But your inspector should have either said yea its OK (cos frankly it nearly is and its pretty insignificant) or you need 60mm or get a U Value Check done.

 

[theoldun]

Seeing as you are Beds, will try to help you out.
If garage is say 3x5 and a perimeter of 16, then your P/A is about right and if existing floor slab is ground bearing you will need 80mm Celotex GA4000 with 25mm TB4000 as perimeter upstand and 75mm fibre reinforced screed to comply with 0.22 W/m2K.
There are only two acceptable ways to insulate a 102mm external brick wall to comply with 0.28W/m2K. Either 72.5 Celotex PL4000 or 75mm Eurothene PL Both the above to be mechanically fixed to 25x50 battens that have been mechanically fixed to existing half brick wall. Both the above to have 6mm plaster skim coat.
Any thing other than above is a hybrid.
You state that you are going to external render wall and that you have erected 50x75mm studwork and filled with 50mm celotex and you intend to plaster board over this. This construction will only give you an R value of 0.29m2K/W and a U value of 0.34Wm2/K which is no good..
To utilise existing 50mm celotex and 75mm studs overboard studs with 37.5mm PL Celotex4000 and plaster skim.
37.5mm PL celotex is 25mm of celotex bonded to 12.5mm plasterboard.
This will increase your R value to 4.03 and give U value of 0.25Wm2/K This lower U value will also compensate for any possible cold bridging.
Any problems, or if you want a breakdown of calculations, then come back.
Regards oldun

 

[mikric]

[/quote]
Well it gets you to 0.31 mikric so it doesn't really comply does it? But the OP's BCO does sound like a t****r though. [/quote]
Well its not far off the threshold value for upgaded elements in ADL1B but then I am always sympathetic on garage conversions, if I like you I think you will find insulation is not classed as a "statutory inspection"anyway, which is probably why they said they wont come back hence my view crack on.
If they query it take some pics when its in place, show them and tell them its 75mm.

 

[garydc]

Thanks all, I am cracking on. No way I'm going back now or making the room any smaller. Need to get done, so I can move onto our extension.

"show them and tell them its 75mm".....i like the sound of this

 

[mac391]

Just call Celotex, give them your dimensions and they will tell you the exact insulation to use in both walls and floor in 2 mins over the phone ..