# Single skin Garage conversion for workshop - advice please



## Mattatooi (7 May 2016)

Looking for some advice, as these forums seem to have a lot of people doing this. 

I have a detached garage (approx 6mx3m), with a flat roof (well slight angle for drainage, but effectively flat roof) which is OSB with felt on top, the gritty stuff. It is single brick (100mm) with 200mm pillars on the long walls. I have 2 windows, up and over door and will be re-opening side door which is currently blocked up (dont know why... prev owner).

Problem I have is, during winter, it gets quite damp. Very drafty etc, and some of my tools have rusted up a bit etc. I want to be able to have tools all out and hanging and organised etc with no danger of damp/rust. I also would love to be able to store wood, so having it insulated seemed to be the best option. There is a washing machine and tumble dryer in there, which will have to stay there. Its a condenser dryer so it produces quite a bit of heat when used.

Looking at celotex costing, it aint cheap! I am thinking roof, 100m earth wool, or 100mm celotex. Obv earthwool will be no where near as good as celotex, but it is way way cheaper. I understand I need to leave a 50mm gap above insulation for ventilation, which also means I need to put holes in between all the joists on the facias to allow air to flow through. I dont have a softit. Just facias. Trying to local water proof small vents is proving difficult. Anyone ideas?

Walls I am thinking 2x2 studs at 600mm cc, with 50mm celotex and floor 2x1s with 25mm celotex. Then on floor, chipboard floor and walls, probably OSB or ply. Maybe plasterboard, but I am thinking having wood would be much more benefical for wear and tear and the ability to hang stuff on walls anywhere.

My current height to ceiling is 2.3m so I do not want to reduce the height too much. 

Now, I really do not know what to do with the up and over door. Replacing it will be very expensive. What about just throwing a stud wall infront of it and locking ti off. Then down the line I could make some hinged doors when the funds are there? Thoughts? What about sealing it from drafts. There are huge gaps around it currently.

On top of this, I will be getting more sockets etc put in. Currently just have a light and 1 double socket. 

Regarding damp proofing. I believe layer of DPM on the concrete floor, ran up on top of a vapour layer which is ran down the walls on top of the studs and insulation before finish ply. For ceiling same again with vapour layer on top of the wall vapour layer. Presume will need to use tanalised timber for all studs. 

Let me know how far I am of here. 

Anyway on top of all that, is all the above really worth it? Is there cheaper options? What about just sealingg the up and over door and putting a vent or 2 and throwing down some vinyl on the floor and put a jumper on? Or just put some stud with no insulation and some OSB on walls. Will this help at all to prevent damp on tools etc? Presume this would not help the temperature, so storing wood would not be the best without insulated. 

Just working out costings, I think I am easily looking close to £1000 on all the work getting insulated?

Thanks


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## RobinBHM (7 May 2016)

For the walls, you could fit a complete layer of 50mm celetex, no studs in between. Then 50 x 25 tile battens over the face and osb board over that. If your walls are porous and get wet, you may want to tank the walls before insulating. With no gaps you will achieve an unbroken layer of insulation and therefore no bridging.

The celetex needs to have all joints taped with silver aluminium foil tape to complete a vapour barrier.

If you make the ceiling a cold roof, it will probably need vents at each void or holes drilled through the joists although Im not sure how effective that would be for providing cross flow ventilation.

The other option, would be to fix the celetex tight to the underside of the flat roof and fill all the gaps and tape where the celetex butts to each joist. This would be a warm roof and would have no void and no need for ventilation. You would have some thermal bridging at each joist and a slight risk of some vapour getting through the joists where it would get trapped at the roof deck -but if you seal well I dont think it would be a great problem.

To cut celetex between joists Ive found it works best to measure accurately, if the joists are not parallel then cut tapered pieces. It can help to cut a slight angle on the insulation.

Its worth ringing round for prices, rigid foam pir insulation is available in a few brands like ecothern, xtratherm, kingspan etc. Sometimes good deals from seconds and co.


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## Woody2Shoes (9 May 2016)

I think your floor probably already has a DPM under it - I suspect it doesn't have any insulation under it. Even if you insulate ceiling and walls (and include ventilation and vapour check), your floor will be a heat-sink and a place where condensation can form. I think that Celotex/Kingpan/etc PU boards - properly installed - are by far the best bang for buck (especially where space, e.g. ceiling height, is at a premium), I also think you should consider insulating the floor slab too. Cheers, W2S

PS a good alternative, which may work out cheaper, is to keep your most important/susceptible tools in a cabinet which can be closed - and to put a heater at the bottom of the cabinet to keep everything above the dew point (usually about 10-12C in our humid climate). The heater could be as simple as an old-fashioned 60W light bulb. A cabinet might also be a good idea from a security point of view.


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## Mattatooi (10 May 2016)

Thanks. What about drying wood? I am wanting to start getting some proper wood for projects going forward and want to be able to get them dried to correct moisture etc. Surely my garage will not aid this? What conditions do i need for this? One reason I was considering going down the insulation route. But I had thought about just making some sealed cabinets for tools for now, as budgeting this seems to be quite a bit. Might need to save up a bit before attempting.


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## Phil Pascoe (10 May 2016)

I have heard of people using old chest freezers for storage - the seals are usually good enough to keep stuff dry. You could put a tub of silica gel in one.


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## skipdiver (11 May 2016)

http://www.secondsandco.co.uk/

Have a look at this site. They sell seconds and factory rejects of insulation board, which is good enough for a workshop and cheaper than shop bought.


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## kostello (12 May 2016)

skipdiver":3keyuufy said:


> http://www.secondsandco.co.uk/
> 
> Have a look at this site. They sell seconds and factory rejects of insulation board, which is good enough for a workshop and cheaper than shop bought.


I have recently got a load of celotex....

I ended up getting it from less2build .

They were about 10% for new less than seconds and co were for their stuff......

It was delivered by SIG insulation, which is who I normally use..


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## MMUK (12 May 2016)

skipdiver":3ctk68ps said:


> http://www.secondsandco.co.uk/
> 
> Have a look at this site. They sell seconds and factory rejects of insulation board, which is good enough for a workshop and cheaper than shop bought.




I've always found them to be horrendously expensive. Their 50mm Celotex, for example, is £3 +VAT more than I pay at Magnet!


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## skipdiver (13 May 2016)

Yeah, just checked and they are expensive for what they sell. It's been a while since i bought any insulation boards but am about to start searching myself as i want to get my shop up to spec before winter now that i am working from home full time. Thanks for the heads up chaps.


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