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Big jim’s Garage conversion and layout thread


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Excellent Jim, looks like loads of thought has gone into this and I wish you well with it.

 

Just some info, when I last did a concrete / Brick Garage a few years ago, I bought some 8ft x 4ft sheets of 2 inch Polystyrene for the floor, then covered that in 3/4 inch thick 8ft x 4ft Chipboard and then in the walk area I laid Halfords interlocking rubber floor mats. No cold came up through the floor and I always had nice warm feet.

 

I'm looking forward to seeing the New Plan develop. 

 

All the best.

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I have allowed for floor insulation in the lining of the building, I wasn’t going to bother as there is a damp course and the floor is fairly level and was going to merely carpet it but for the sake of a few crossmembers, polystyrene and chipboard I may as well do the job properly or i’ll regret it futher down the line

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I have allowed for floor insulation in the lining of the building, I wasn’t going to bother as there is a damp course and the floor is fairly level and was going to merely carpet it but for the sake of a few crossmembers, polystyrene and chipboard I may as well do the job properly or i’ll regret it futher down the line

 

Definitely go for some insulation on the floor Jim - the damp will be stopped by the damp course but the floor will still get cold and so will you if you're in there for any extended periods.

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Definitely go for some insulation on the floor Jim - the damp will be stopped by the damp course but the floor will still get cold and so will you if you're in there for any extended periods.

For the benefit of anyone contemplating a garage reroof, I am a fan of the bitumen sheets. I would suggest that the manufacturers instructions of a minimum 10 degrees and supporting rafters every 60cms are followed. I have hands on experience of sorting out two or three badly installed roofs as well as three "new build" garages. One issue is condensation after snow leading me to line the roof of my modelling corner with thin ply.

If I were to start from scratch, I would copy my daughters stables which have bitumen sheets over an 11mm OSB base.

The decision to raise the floor of the modelling area with a green chipboard floor has not been regretted.

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And there it was, gone

 

5535B142-6C32-4AC2-9862-A95FFFD00745.jpg

 

The bitumen sheets have been very good over the last 8 years, they were originally laid on rafters but then subsequently removed and refitted on top of 10mm chip board, having taken that down today 2 from the centre of the garage are reusable but the edge pieces are all starting to go on the outer edges, the edge that was exposed to the elements behind the facia

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Nice one Jim,

 

That's pretty much how I've done things. 12.5ft layout "side" and 4ft "garage" side with a stud wall in between. Progress has been slow with trips away ar sea, but that 4ft space is surprisingly large. I put shelving up in there 3 weeks ago and was pleasantly surprised with the outcome. Just got to finish off now and build my layout!

Good luck with it

 

John

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Beams beginning to be fitted, 3 more to go and then boarding out and fibreglassing, we have managed to reuse all the existing beams but by the time he had done that lot the local timber shops were shut to get the remaining few

 

D7468AA7-91A8-4882-B194-2A6EA7C8BE9B.jpg

 

At the door end I’m going to get him to attach a piece of 2x2 to the underside of the board to enable me to attach a upvc facia (and framing) between the door top and roof

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Forgot to update this last week before I went away for the long weekend, the wood and edging is in place and I was hoping the guy would have fibreglassed it Saturday but he has been busy and promises he will do it Tuesday so when I get home from work tomorrow evening I shoildnwith any luck have a completed roof!

 

70E6C42F-DEB6-46D4-8A85-6C4FB0413B21.jpg

 

Been a long drawn out affair, 2 days has turned into almost 2 weeks but on the plus side it’s almost payday again so I can crack on and get the wood I need next

 

Got someone coming round tomorrow to see about fitting the doors (and removing the garage door too)

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So the roof is done, just going to have to watch where water has settled at the near corner but it’s looking good

791F1928-8CE6-4CB0-9B68-49A604D09ED2.jpg

 

Guttering to refit to the one side as well

 

You can just make out an extra beam in the doorway, that’s where the bi fold door will sit below, about 1/2 a brick back from the front of the garage, the void between the top of the door and that beam will be filled with facia board and insulated

 

Had a builder round earlier who I’ve used before who is going to fit the door for me, is in fact a neighbour, and I mentioned about the battening out inside and he mentioned using insulated plasterboard instead which will mean it won’t need battening as it is bonded directly to the wall, says he could do it in a day or two including fitting the door, I’m going to speak to the building inspector tomorrow and see if that idea is ok, what depth of insulation is needed etc, the builder suggested 50mm should be enough but depends on what the inspector says, looking at the cost of the boards they are not much more than plain insulation sheets and what i will save in additional wood and plasterboard costs I can put towards labour to do the job right first time

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So the roof is done, just going to have to watch where water has settled at the near corner

 

 

Nothing to worry about, the felt joints create small trays where the water can sit, as well as capillary action creating the pools. There are comments from the manufacturers that some moisture on the material helps to keep it cool.

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Had a builder round earlier who I’ve used before who is going to fit the door for me, is in fact a neighbour, and I mentioned about the battening out inside and he mentioned using insulated plasterboard instead which will mean it won’t need battening as it is bonded directly to the wall, says he could do it in a day or two including fitting the door, I’m going to speak to the building inspector tomorrow and see if that idea is ok, what depth of insulation is needed etc, the builder suggested 50mm should be enough but depends on what the inspector says, looking at the cost of the boards they are not much more than plain insulation sheets and what i will save in additional wood and plasterboard costs I can put towards labour to do the job right first time

It might be a good idea to check the detail with the inspector.  I wonder if there's been a little talking at cross purposes there?  Having the insulation bonded to the plasterboard certainly makes installation easier (at a cost) but I think you will still need battens on the wall to create an air gap.

 

For my garage conversion I discussed the approach with the inspector first and more-or-less did exactly what he suggested for the whole job.  I used separate insulation and plasterboard (simply because it was cheaper) but there was no ambiguity about whether or not I needed an air gap and the battens were not just there to attach the insulation and plasterboard to.

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I’ve just got off the phone with the building inspector, he seems to think 75mm insulated plasterboard would be fine but he’s not so sure about 55mm off hand

 

He’s coming to inspect the work done so far on Friday so will see what happens then

 

I did wonder about the airgap too but he sees happy enough bonding or the wall

 

Teaky: price wise there doesn’t appear to be much difference in the price of the insulated stuff compared to plain insulation where I’ve looked

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I had my kitchen outside walls lined with  polystyrene insulated plasterboard. This was fixed with blobs of plaster so there is some air circulation between insulation and wall, (As long as you have air bricksin the outer skin...).

Has anyone considered the option of a stepped wall between the workshop and utility room, so that the appliances  can effectively be tucked underneath part of  the layout? Might gain a bit of space for the layout.

 

Thanks

 

Dave

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I’ve just got off the phone with the building inspector, he seems to think 75mm insulated plasterboard would be fine but he’s not so sure about 55mm off hand

 

He’s coming to inspect the work done so far on Friday so will see what happens then

 

I did wonder about the airgap too but he sees happy enough bonding or the wall

 

Teaky: price wise there doesn’t appear to be much difference in the price of the insulated stuff compared to plain insulation where I’ve looked

OK, I've just double checked.

 

I can't remember which suppliers I used when I did the garage but for my current loft conversion I bought the insulation from insulation4less and the plasterboard from Wickes.  A quick look suggests 50mm Celotex is £21.65+VAT and plasterboard is £6.51 giving a total of £32.49.  A sheet of 62.5mm combined PIR & plasterboard is £45.80+VAT, so there is a £22.47 difference per 2.4 x 1.2m area.

 

Now there are differences here which need to be costed in.  For me there was no labour cost, so I could ignore that, whereas you are probably going to save something there.  I'm not sure how much you'd need for your garage but insulation4less charge for delivery below £300 which didn't affect me because I needed quite a lot.  I'm probably more of a skinflint than you too.

 

Another key point is that Celotex (I haven't checked other manufacturers tonight but I checked all of the major ones when I did the garage) don't do the bonded sheets thicker than 62.5mm (50mm PIR + 12.5mm plasterboard) so if the BCO says you need 75mm then you'll need another 25mm PIR somewhere.  He may not though.  As advised by the BCO, I put 75mm in plus air gap when I did the garage but it is a habitable room joined to the house whereas your garage is separate and you are trying to create a comfortable hobby room.

 

Whilst we're talking insulation I'll just mention that there's 100mm PIR in the floor and 150mm in the ceiling (flat ceiling beneath an uninsulated loft space and a pitched roof).

 

One last thing I've never understood with the bonded boards is how you seal the joints?  With the separate sheets of PIR, you put aluminium tape over all the joints to ensure the integrity of the vapour control layer.

 

Hope this helps.

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just had a look at insulation for less again, the building guy said i'd need 75mm thick if i go for the batten option, that is priced as £31.45 plus vat, (£37.74)

 

my bulder can get the 55mm bonded plasterboard sheets for around the £50 mark so around £13 difference, if as im hoping the building guy says the bonded stuff can go straight on the wall without battens i will save around £300 on wood but more crucially i will save a hell off a lot of time

 

the crazy thing is he's currently going on about the wall insulation maybe not being up to standard but i dont have to do anything about the ceiling, i could leave it as bare beams if i wanted and similarly the floor i dont need to do anything about that either!

 

its now being classed as a 'habitable room' by the council, rather than a 'comfortable hobby room'

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This isn't a like-for-like comparison Jim.  Assuming that when your builder says "55mm bonded" he means the nearest thickness i.e. 52.5mm, that is 12.5mm plasterboard bonded to 40mm PIR.  Bonded or not, the insulation value is exactly the same.  You are simply paying extra for the ease of handling.  So, based on the insulation4less prices that's £43.10+VAT=£51.72 for the 52.5mm bonded sheet (i.e. similar to the price your builder can get it for) compared to £20.20+VAT=£24.24 + £6.51 for plasterboard bringing it to £30.75 in total if using separate materials (plus extra labour and battens).

 

The thing is though, the air space created by the battens is part of the insulation calculation which means that bonded board fixed directly to the brick wall has a lower insulation value.

 

The insulation in the ceiling and floor makes no sense to me at all.  If you don't insulate those then there is no way you're going to comply with Building Regs.  In fact, both the roof and floor need to achieve higher insulation values that the walls.

 

Here's the current Building Regulations Approved Document covering insulation: BR_PDF_AD_L1B_2015_insulation.pdf

 

Logic suggests that if you are only insulating one element then you start with the roof.

 

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You could simply take the approach that as long as the BCO gives you a certificate for the completed work then that'll do.

 

If this was my garage, I'd want to understand things and would be asking the BCO to explain in plain English what standards were being aimed for and how the proposed solution met these standards.  It may well be that the target for a standalone outbuilding is lower than for an extension to a house.  That's fine but I still can't grasp why you'd be insulating walls and nothing else.  Don't forget, the BCO is on your side and there to ensure that your builder's work is up to scratch.  That's what you've paid for with your fee.

 

This is all just my personal opinion and don't forget I'm only an amateur who has read the regulations rather than a professional who is obliged to know them.

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Honest to god the roof and floor bit is what baffles me too, why go to the expense and compliance of doing the walls but not have to do those!

 

As I say he’s coming out tomorrow to have a look at the roof (even though on his initial visit he said I didn’t need to see him until the batterning was up) but from my point of view I want clarification of what I do and do not need to do should I go down the insulated board route

 

Going back to the wall insulation then the builder said its 50-55mm insulation (depending on brand) PLUS the 12.5mm plasterboard, similarly the thicker stuff is 75mm plus the 12.5mm board

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Right, so a different building inspector turned up today and has given me contradictory advice to the first one!

 

As teaky suspected the bond to the wall method I wanted to go down also involved having to add battens to the wall so with that in mind the job is not cost effective so I’ve decided to back to the original plan of fully battening it out and adding the insulation separate to the plasterboard

 

However the bit that has thoroughly p’d me off is the roof, after the first guy said it wouldn’t need insulating as it’s jot covered by building regs this one has said it does, I was planning on doing it anyway so not a huge hardship I thought “i’ll Plasterboard it up but add rock wool in the void” I said, “oh no it’s got to be 125mm thick insulation with a 25mm airgap!

 

So what was a simple(ish) board and fill job is now needing 100mm thick insulation between the beams and 25mm/12.5mm insulated plasterboard below the beams to allow there to be the air gap

 

Probably just added a good £200 of materials to the job!

 

He has suggested a floating floor 25mm kingspan insulation with boards on top, also mentioned adding a membrane when I do it but also a thin strip of DPC to the bottom of the battening as I fix it in place, as well as of course the wall membrane

 

Also picked up the double opaque glass panels for the doors

42BA8C0A-C007-4823-B843-AB92F75D4717.jpg

 

BADB533E-CDFA-4DC4-9BF0-20C210DBEB01.jpg

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Hmmm ....... why does it need to come under the regs?

 

It’s a ‘shed’, isn’t it?

 

That having been said, I converted our garage for similar purposes (nominally ‘utility’, actually ‘layout’) and used good thick insulation, all round, and of the ceiling, and am very glad I did. It’s very cosy in winter, costs next to nothing to keep above condensation temperature, and is cool in summer. Remember trickle ventilation, though.

 

Our local council has very good, clear, guidance on-line as to what is and isn’t covered by the Regs, and what does and doesn’t need planning permission, so it might be worth checking to see whether your council has too.

 

Kevin

 

Mine was exempt from all requirements except Part L, under Item 1 of the clause posted below, but it looks as if yours might get caught because it is against a boundary line. And, it was exempt from Part L as in Item 3.5(d) of this https://assets.publishing.service.gov.uk/government/uploads/system/uploads/attachment_data/file/540329/BR_PDF_AD_L2B_2013_with_2016_amendments.pdf

 

Worth checking, because I think yours will be exempt from Part L (which covers insulation) on the same basis ...... it’s less that 50sq.m and not a dwelling.

 

“Small detached buildings

 

1. A detached single storey building, having a floor area which does not exceed 30m2, which contains no sleeping accommodation and is a building—

 

(a)no point of which is less than one metre from the boundary of its curtilage; or

(b)which is constructed substantially of non-combustible material.

2. A detached building designed and intended to shelter people from the effects of nuclear, chemical or conventional weapons, and not used for any other purpose, if—

 

(a)its floor area does not exceed 30m2; and

(b)the excavation for the building is no closer to any exposed part of another building or structure than a distance equal to the depth of the excavation plus one metre.

3. A detached building, having a floor area which does not exceed 15m2, which contains no sleeping accommodation.”

Edited by Nearholmer
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On the positive side Jim, at least you now know what to do.  That's assuming Nearholmer hasn't chucked a spanner into the works with his possible exemption, of course.  Better insulation = less energy for heating.

 

Don't forget to check if the floor is level.  It's worth fiddling about with a few simple spacers to level things up.

 

Nearholmer also makes a good point about background ventilation.  You don't need much though.  Trickle vents over windows or a simple through-wall vent will do the trick.  If you do the latter it might be easier to cut the hole in the brickwork before covering the inside.

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