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Garage - insulation?


curlewhouse

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Along with the house, our architect designed a standalone two skin blockwork garage with 55mm cavity (to be covered in planking when finished as we are in an area where everything has to be natural stone otherwise, so expensive) with a  beam and block and slab floor. I'm just starting to build it, and am wondering if I'm required to insulate it? Common sense would say not, but then this is the UK, so that means nothing. I could ask our BR guy of course, but in my experience of self build to date, absolutely any question you ask of  anyone in authority is always answered simply by whatever will cost you the most if they have an option of answers. So do I have to insulate an unheated building under the regs?

Edited by curlewhouse
Spellink Korrections!
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Guest Alphonsox

Easy answer - no, you are not required to insulate a detached garage. You may want to if you are intending to spend any time in it as a workshop etc, or you could just put on a jumper. We have just completed an uninsulated double skin garage to the complete approval of building control.

BTW > I'm not even sure it needs to be double skin.

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Cheers.  No, I don't think it needed to be double skin either, but that's what went in on the plans and TBH I never gave it a thought until I came to buy the blocks - and then thought "why"?  I did mention to the architect that I may actually use it as a workshop and possibly partition part off as a deer larder, so perhaps he was thinking I'd want to insulate it so went with a cavity.

 

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  • 7 months later...

On the same sort of tack I am about to construct our garage floor/base, this is planned to be insulated with 100mm of PIR with a 100mm solid concrete slab in fibrecrete crack resisting mix, the whole slab will be reinforced with sheets of A142 mesh, I know I need to add a DPM but I'm not sure if it needs to be between the compacted crushed concrete sub-base or on top of the PIR (celotex or similar) if anyone can steer me in the right direction I'd be most grateful.

 

BTW it's an integral garage that will be 100mm lower than the finished floor of the house due to building regs, the building inspector doesn't seem to be that bothered about the construction so I feel that I'm not really able to pose the question with him, his last comment on his last visit was "as the garage is a non habitatal space they don't have any jurisdiction"

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31 minutes ago, Oz07 said:

2 layers of dpm if pir insulation.

Wow two layers, makes sense I guess, I'm also guessing that the top layer of dpm would need to be dressed into the dampcourse of the internal blockwork, we've opted for a double skin construction with full rockwool insulation to "future proof the garages which could be converted into livable spaces at a later stage if so desired.

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I’d ditch the rebar and go for 150mm concrete - much easier and 100mm isn’t that thick when it comes to a garage floor

 

Ours is 200mm in the middle and has a 300mm thickened edge as we used it as the dumping point for the rest of the slab when we ordered the concrete ..!

 

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1 hour ago, Onoff said:

Just remember with a garage.....it's very little effort to incorporate UFH pipes in the slab. For future habitable space or just more comfortable working on your classic Ford!

Agree, though not the Ford bit....................................

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Good point may well consider doing that?with the UFH piping although I haven't got a classic Ford just a rather juicy 3.0 litre Audi Allroad ?

And 150mm of concrete would be difficult to achieve now without digging up all the prepared sub-base and redoing it all again, can't go higher as we wouldn't be able to get the 100mm step down plus the A142 was specified by the structural engineer due to a bit of dodgy ground in one corner, may go for 10mm mesh to be sure as it is a totally floating slab

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59 minutes ago, Peter M said:

Good point may well consider doing that?with the UFH piping although I haven't got a classic Ford just a rather juicy 3.0 litre Audi Allroad ?

And 150mm of concrete would be difficult to achieve now without digging up all the prepared sub-base and redoing it all again, can't go higher as we wouldn't be able to get the 100mm step down plus the A142 was specified by the structural engineer due to a bit of dodgy ground in one corner, may go for 10mm mesh to be sure as it is a totally floating slab

 

Too late now but I'd have put a pit

in if only a shallow one. 

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Oohh now there is something that I definitely didn't think about, a pit, would have been so easy to plan and construct, boy do I feel like an idiot, but then again with the high water table that we have here that would have created loads of extra issues and concerns that would have cost us such as tanking and sump pump to name just two, not to mention the tight budget that we're working to.

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9 hours ago, ProDave said:

I installed a pit. Only shallow at about 1 metre deep, so that when sitting (on a duck board) my eyes are about level with the floor.  Makes simple things like an oil change a whole lot easier.

 

What did you use to cover it?

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Not really relevant but whilst we were looking at the site on Wednesday we noticed that the very efficient bricklayers had put insulation in the cavity of the side of the porch which is open to the elements.

 

Detached garage does not need insulation as stated.

 

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On 10/31/2017 at 22:02, Peter M said:

And 150mm of concrete would be difficult to achieve now without digging up all the prepared sub-base and redoing it all again, can't go higher as we wouldn't be able to get the 100mm step down plus the A142 was specified by the structural engineer due to a bit of dodgy ground in one corner, may go for 10mm mesh to be sure as it is a totally floating slab

Do you really need the 100mm step down?

https://forum.buildhub.org.uk/topic/2891-integral-garage/?tab=comments#comment-44265

 

A couple of quotes from the above thread:

"the garage floor can be level and the house level but there must be a height difference between the two, the height difference can be made up with a slope rather than a step"

 

"We have the same and have a 50mm fall in the slab towards the garage door over a distance of about 5m"

 

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Quote from Part B of the Building Regs:

 

5.5 Where a door is provided between a dwellinghouse and the garage, the floor of the garage should be laid to fall to allow fuel spills to flow away from the door to the outside. Alternatively, the door opening should be positioned at least 100mm above garage floor level. 

Edited by Ian
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