# How should I insulate workshop walls?



## Triggaaar (28 Oct 2010)

Hi all

I've got a new 20' x 6'6" workshop, attatched to a new guest house.
The joining wall is a well insulated stud wall, with 12mm ply on the inside.
I've insulated the sloping roof with about 170mm rockwool, with 11 OSB underneath.
The floor is just the concrete base, will a floor levelling compound and DPM, and I don't want to insulate it (not worth it, since the floor finsh is as I wanted it).
The front of the shops is just a pair of FLBs, which I will add a small amount of 25mm insulation to.

I'm wanting to insulate the remaining back and side wall, and I'm not sure whether to
a) use battens with celotex in between (no void), then OSB on top
b) use battens with celotex on top (leaving a void), then OSB on top of that.

ie, I don't know whether I need to leave a void between the walls and the celotex.

The walls are only half thick brick, rendered on the outside where they are exposed (but not fully rendered). They are always dry to touch, although I haven't used a damp meter on them.

I'm also not sure whether to go for 1" or 2" celotex, I'm not sure if it'll make a lot of difference, since I'll not be trying to keep it warm when I'm not in it, I just want it to warn up once I'm in with a radiator (electric) on.

So what do you think:
void or no void?
1" or 2" of insulation?

Any help much appreciated
Thanks


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## johnf (28 Oct 2010)

Hi Trig

Put celotex against wall (no Battens) osb on inside stagger all joints between osb and celotex and fix with masonry screws these no need for any vapour barrier as the osb and celotex do it for you
the thicker insulation the better


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## Triggaaar (28 Oct 2010)

johnf":6llt6old said:


> Put celotex against wall (no Battens) osb on inside stagger all joints between osb and celotex and fix with masonry screws these no need for any vapour barrier as the osb and celotex do it for you
> the thicker insulation the better


Ah, very interesting stuff, thanks.

I've already made the order - 50mm insulation, 11mm OSB. I've also order 2x2 studs, but I might be able to cancel that first thing before it arrives.

I need to do it tomorrow (got a helper), are these screws available in either builders merchants or DIY sheds?

And any advice on how often I need to fit them (I think OSB can warp if not controlled)?


Thanks, much appreciated


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## johnf (28 Oct 2010)

Fixings say 450mm centers or what ever you are happy with 
masonry screws 122mm or 132mm long needs a 6mm drill
toolstation are a good price there is one in hove

Toolstation UK Brighton & Hove
Unit A,
Peacock Trade Park,
Lyon Close,
Hove,
BN3 1RX.


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## Triggaaar (29 Oct 2010)

Excellent, thanks John.

I've just been reading Kinspan's online guide. They generally recommend using battens behind their board, and only fixing directly to masonry for cavity walls (see here).

Is there a reason you think the battens are unnecessary?

Thanks


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## johnf (29 Oct 2010)

Hi Trig

The link is for dry lining board (thats plasterboard with kingspan on the back)

my method is for a workshop quick and simple full cover insulaition the osb provides the fixing for shelves ect it's what I did in mine it's been there 6 years now no problems it also saves you money


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## lemonjeff (29 Oct 2010)

John,
Your solution is ideal for my workshop, what thickness of osb did you use ?

Jeff.


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## Triggaaar (29 Oct 2010)

johnf":k44lcdju said:


> The link is for dry lining board (thats plasterboard with kingspan on the back)
> 
> my method is for a workshop quick and simple full cover insulaition the osb provides the fixing for shelves ect it's what I did in mine it's been there 6 years now no problems it also saves you money


Yeah I saw it was K18, but I think their principle is the same. No matter, I was happy with your suggestion (plus I didn't have 1" battens) so I've done it. I didn't bother with masonry screws in the end, I tried it with raw plugs and the screws I had to hand, and it worked fine. If it does every suffer from damp, it's not a big job to take it off the walls and fix it.

It's only 11mm OSB, so I'm not sure what kind of hooks I can attatch. Most of the area will have standing shelving units next to them, but I'll be fitting a few hooks. Got to paint it all first though.

Thanks again for the help.


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## johnf (29 Oct 2010)

Iv'e got a huge amount of stuff hanging on mine timber racks , shelving ,ect no problem

Lemonjeff 11mm osb


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