# shed insulation



## fraser

Hi,

I have just built a 12 x 8 shed on a concrete base in the garden and the next step is to insulate it. Hopefully next weekend! The walls of the shed are 22mm loglap, so a bit heftier than your average shed off the shelf I suppose. The shed is close to the fence between myself and the neighbour, so I have to consider sound as well as heat insulation. It will be used for furniture making, so it needs to be kept dry and at as close to a constant temperature as I can manage. There will be small machines such as a planer/thicknesser, table and band saw, etc nothing too heavy, but these tend to be the noisiest in my experience! I wondered if anyone would be able to help me with the insulation options, I have had a good look on the internet but looking for those who have actually used the products.

My first thoughts were to use 50mm Rockwool sound insulation then cover with 6/9mm birch faced ply. This is still a possibility however at £15 a sheet of ply the cost starts to rack up. My preference obviously is not to spend a small fortune but will consider all options. Could anyone recommend anything or give me some tips? 

Also, should I insulate the floor? Is this necessary?

Any help would be great!


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## fraser

Someone help a guy in need :?:


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## Rob Platt

fibreglass and the cheapest sheet material you can lay your hands on. birch faced ply is too expensive have suggested visqueen on another post. windows and doors will let the sound out just as well as your walls and insulating the walls for sound might not be as affective as you think.
all the best
rob


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## fraser

is that sheets of fibreglass rob? what is visqueen? so what do you suggest for windows and doors? do you believe it's not possible to get decent sound insulation because of this?


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## Rob Platt

your doors and windows will let the sound out. visqueen is plastic sheeting the sort used as a damp proof membrane under concrete. what it does do is provide a cheap barrier between you and the insulation so it keeps the insulation in place and stops you having to breathe it. it has no structural use whatsoever. all the best
rob


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## fraser

Ok that sounds good Rob, thanks very much. Will look into that tonight.
Any other suggestions from anyone to keep me busy?


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## m1ke_a

I will hopefully following you in the next few weeks and was thinking about celotex board for the insulation, and maybe OSB3 for the interior walls?

I will watch this thread with interest


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## MickCheese

If it were me and I was trying to do it for as little as possible I would look at glass fibre loft insulation covered by plasterboard with a vapour barrier.

A bit of skirting board at the bottom just to finish it off.

Visqueen is OK but you cannot fix anything to it and it may promote condensation on the walls.

Just my thoughts, I am no expert.

Mick


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## fraser

Hi,
Thanks very much for your replies

Could you elaborate on the glass fibre insulation please? I have considered plasterboard and will be looking into it.
Am a bit concerned that it is going to get dinged to death but that is the least of my concerns i suppose.

Does celotex have sound properties?

I have just made a call about rockwool, so will be making enquiries about other products next.

Thanks again


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## fraser

and osb3- this is exterior sterling board correct?


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## m1ke_a

fraser":2qaiujh5 said:


> and osb3- this is exterior sterling board correct?



Yes, as I understand it. One of the firms in my other thread said they'd do their roof with that with Ondulite sheet on the exterior.

I might also look at Roc Slab / mineral wool slab. I put a load of it in between floor joists and a false stud wall for sound insulation / warmth in the house a few years back.

Fun stuff to fit (you cut it with a bread knife or similar!)


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## MickCheese

I was referring to rolls of glass fibre loft insulation, the really itchy stuff.

On a previous shed build I just stuffed it between the uprights, then a vapour barrier of polythene, then the plaster board.

Mick


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## fraser

I haven't looked up the loft insulation yet-how did u rate that? maybe not so good if you haven't carried on using it?! how did the polythene fair? Did you get condensation on the walls? What have you used more recently? 

Will look up the roc slab thanks-as long as it keeps the timber warm and dry! From the name it sounds like a board material? Will have a look tonight. The problem is also getting the stuff over to the isle of wight. we are limited to shops over here


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## m1ke_a

fraser":fh6mcoox said:


> Will look up the roc slab thanks-as long as it keeps the timber warm and dry! From the name it sounds like a board material? Will have a look tonight. The problem is also getting the stuff over to the isle of wight. we are limited to shops over here



Think of the Roc slab as dense firm loft insulation. It isn't solid but has definite shape and form which means you can install it vertically in wall voids etc. IIRC I got mine from Jewsons about 6 years ago.


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## MickCheese

fraser":2hk2wqcu said:


> I haven't looked up the loft insulation yet-how did u rate that? maybe not so good if you haven't carried on using it?! how did the polythene fair? Did you get condensation on the walls? What have you used more recently?
> 
> Will look up the roc slab thanks-as long as it keeps the timber warm and dry! From the name it sounds like a board material? Will have a look tonight. The problem is also getting the stuff over to the isle of wight. we are limited to shops over here



We now have a log cabin but did use loft insulation in the last two sheds I erected, it worked OK. My wife works from home and each time we have moved house we have erected a new shed for her to work from.

Be careful with the solid Roc-Slab if it is just a little too thick for the space you have available it will either push the shiplap off the outside or make the plasterboard bulge. The loft insulation is quite easy to cut and compress into the space.

Mick


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## fraser

Mick, thanks very much

Do you know how the fibreglass board compares to something such as rockwool?


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## Blister

When I did my garage I used 

2" x 2" battens 

50mm celotex insulation boards ( Or similar make ) 

And OSB 8 foot x 4 foot boards ( Painted with primer / undercoat / top coat ) 

Its important to do inside the roof as well as heat rises and fill any gaps with expanding foam ( seal all the joints ) 

Then its amazing at how little heat you need to keep it warm 

link to my project re insulation 

what-s-blister-up-too-now-t34753.html?hilit=garage


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## fraser

Ok great thanks very much! Was a good read and gives me a few ideas...
What about the floor, it is worth doing? I am leaning towards yes but who knows....
I have just rang b and q, pretty useless as always but they do have:

Normal rockwool £3 for 5m2
Soundproof plasterboard £14 12mm 8 x 4 sheet-is either that or ply/chipboard of some degree
Knauff fibreglass roll, thick stuff though not sure it will squish down enough
And an incapsulated roll, which has foil, polystyrene and fibreglass within it for £10 5.5m2
Didn't have celotex, believe the knauff was the nearest alternative. 
Can get some polythene easy enough if it's worth using. 

Will be giving a couple of other places a ring but they will have the most choice I suppose. Going to be quite expensive going down one of those routes but heyho.


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## fraser

Blister, regarding this comment on your thread:

'One thing to keep in mind when you insulate the roof is to leave an air gap between the insulation and roof and a route for outside air to circulate. This will stop condensation forming and consequential damp problems. '

What did you do for this? Simply fix your insulation to your joists on the roof, rather than between them? So that you have a gap between the joists? What did you do for the route for outside air to circulate??

Have got a few more prices and produsts:

A rockwool slab rather than roll pack of 12 @ 1200 x 600 £31 plus vat (anyone know the different in properties between the slab and roll???)

Ecotherm-bit too pricey I think and he didn't sound too sure of this as a good idea on the phone

Polystyrene board 2" 8 x 4 sheet £13

Recticell (think this is what Blister used??) 50mm thick 1200 x 450 £3.82 a sheet


Any comments??


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## Blister

fraser":2kna8q0u said:


> Blister, regarding this comment on your thread:
> 
> 'One thing to keep in mind when you insulate the roof is to leave an air gap between the insulation and roof and a route for outside air to circulate. This will stop condensation forming and consequential damp problems. '
> 
> What did you do for this? Simply fix your insulation to your joists on the roof, rather than between them? So that you have a gap between the joists? What did you do for the route for outside air to circulate??
> 
> Have got a few more prices and produsts:
> 
> A rockwool slab rather than roll pack of 12 @ 1200 x 600 £31 plus vat (anyone know the different in properties between the slab and roll???)
> 
> Ecotherm-bit too pricey I think and he didn't sound too sure of this as a good idea on the phone
> 
> Polystyrene board 2" 8 x 4 sheet £13
> 
> Recticell (think this is what Blister used??) 50mm thick 1200 x 450 £3.82 a sheet
> 
> 
> Any comments??




All I did in the roof insulation panels was cut some strips and glue them with double sided tape to the top ( roof side ) of the panels to hold the panels away from the actual garage roof


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## pip1954

hi i have just done my garage i used 3x2 timber kept just of the outside with 100mm loft insulation (b&Q) the roof is pitched so i did the ceiling with 200mm loft (some can be split into two 100mm pieces)
still got a bit to do but seems to work for warmth and noise the garage is precast concrete .that's the way i would go .
all the best pip


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## fraser

Pip, my joists are only 2 x 2", I doubt 200mm insulation squishes down that much does it?
Thanks


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## fraser

Blister, what is OSB8? Can't find any info anywhere...

Notes and links so far from thread

*INSULATION*

*Glass fibre loft insulation*-will compress and easy to cut. Knauff from B&Q may not squish enough (200mm -→ 50mm??) £3

http://www.diy.com/nav/build/insulation ... m-11127503

or 

http://www.diy.com/nav/build/insulation ... m-11127504

*Celotex*-can't find a dealer that sells it and delivers down here so far
*Roc slab/mineral wool slab*-needs to be right thickness and doesn’t compress
*Normal rockwoo*l £3 for 5m2

http://www.diy.com/nav/build/insulation ... n-11797516

http://www.diy.com/nav/build/insulation ... m-11917543

*Encapsulated rol*l (polystyrene, foil and fibreglass) £10 5.5m2
*A rockwool slab pack *of 12 1200 x 600 £31 plus vat (7.2mx1.2m)
*Polystyrene board* 2400 x 1200 x 50mm sheet £13 
*Recticell* 1200 x 450 x 50mm £3.82 a sheet

+ *vapour barrier*??? visqueen…polythene

*COVERING BOARD*

*Soundproof Plasterboard *£14 12mm 8 x 4 sheet Cheaper than ply-could be painted white or off white
*OSB3-*external sterling board-9mm £16??? perhaps looks better than plasterboard but not as good at the job?
*OSB8*
*Birch faced ply*-good aesthetics but too expensive

+ *possible under and top coat*


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## JakeS

fraser":23z12hic said:


> Blister, what is OSB8? Can't find any info anywhere...
> 
> *Glass fibre loft insulation*-will compress and easy to cut. Knauff from B&Q may not squish enough (200mm -→ 50mm??) £3



OSB is "Oriented Strand Board" - it's that sheet stuff that looks like it's been 'painted' with lots of little shreds of wood - it's 'oriented' because all the shreds are laying in the same plane. Often used for boarding up broken windows and so on. Yes, as I understand it it's the same stuff that also gets called Sterling board. (He didn't mean "OSB 8", he meant "OSB, in 8x4' boards".)

If the Knauf stuff you're looking at is their 'Space Blanket' product, then yes - it will compress to 50mm. It comes at most at that thickness in the roll, if not less than that. But I expect you'll lose half the insulation property with it compressed, as part of the benefit will come from the air gaps in between the fibreglass strands.


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## fraser

Hi Jake,
Thanks very much for your reply. I understand about the board thanks, no wonder i couldn't find it.

Regarding the Knauff, are you staying the space blanket comes in at 50mm in the roll? If so then i would
not need to compress it as such as i have a 50mm space to fill. Or are you saying even this is too tight a fit for it to give 100%? Otherwise I'm not sure I see if it's worth getting if i am to loose half of it's properies. 

There are other Knauffs i was looking at, one was 200mm and I think some of the Rockwools were similar. I take it this writes them off as they would need to be compressed.

Thanks


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## JakeS

fraser":3hh62859 said:


> Regarding the Knauff, are you staying the space blanket comes in at 50mm in the roll? If so then i would
> not need to compress it as such as i have a 50mm space to fill. Or are you saying even this is too tight a fit for it to give 100%? Otherwise I'm not sure I see if it's worth getting if i am to loose half of it's properies.



I used the Knauf 'Space Blanket' rolls to insulate half my loft a few years back; they come rolled up and compressed, and when you first unroll them they stay compressed for a while before slowly expanding to full depth over time. The compressed thickness is probably 30-40mm, from memory - so they could certainly stay in a 50mm gap, to the point that when I first unrolled them I wondered if I'd have to put a second layer down! My joists were - IIRC - 150mm tall, and there was a layer of some kind of foam pebble insulation on them when I started, I'm certain the compressed Knauf stuff didn't come over the half-way point and could definitely have been squished some more if necessary. It expanded over the course of about a day, IIRC, to reach its final height.

I doubt that compressing it to 50mm would stop it from insulating at all, but I'm sure it would reduce its effectiveness. It may even be the case that after a certain level of compression you'd be better off using (probably cheaper) expanded polystyrene.


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## fraser

Jake, thanks very much for that. I am going to try and head up to b&q tonight to have a look for myself. I doubt if anyone up there has any further knowledge about how compression affects the Knauff but will ask anyway. By expanded polystyrene do you mean the jablite polystyrene boards that you by at b&q? just regular polystyrene boards? This may be cheaper your right, and we did use this at work to insulate a steel shed and it has worked really well.


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## JakeS

fraser":1rsalh6d said:


> By expanded polystyrene do you mean the jablite polystyrene boards that you by at b&q? just regular polystyrene boards?



I don't know any brand names, but expanded polystyrene is the one made up of lots of little bobbles formed into a board - similar stuff to the stuff you used to get electrical equipment packaged in. It's dirt cheap and you'll often see large 8x4'/6x4' sheets in DIY shops. Usually breaking around the edges 'cause it's really fragile!

There's also extruded polystyrene, which is a closed-cell foam similar in appearance to the inside layer in the Celotex 'sandwich'. You'll often find smaller boards around 40-50mm thick, often coloured pink or blue - in DIY shops, but it's more expensive than the expanded stuff. I believe it sits somewhere between expanded and fibreglass or Celotex in terms of insulation, but I could well be wrong.


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## fraser

Thanks very much for your reply Jake, thats what I thought. Though I did believe the idea of open cell insulation was better than closed...who knows.

I have just been to B&Q to see what they have and speak to someone there. They can order Celotex but it takes 28 days so it looks like that is a nogo. 

The options really are as follows. 

-They do a Space loft insulation roll that is 100mm thick, so this may solve the problem of compressing the glass fibres too much and loosing its insulation properties. It may loose some by squashing it 50mm, granded, but a much better proposition than the 200mm stuff and could possibly be the way to go. This is £17 for 13.89m2, which is pretty reasonable.

-The encapsulated roll (polystyrene foil and glassfibre) £10 5.5m2 (haven't actually seen this yet-is at another store which I can only get to at weekends)

-Polystyrene board 8 x 4 50mm sheet £13

-Recticell 1200 x 450 x 50mm £3.82 a sheet (haven't seen-same for encapsulated)

Rock wool, apart from the loose lay, comes in 170-200mm thicknesses so I think this probably rules that one out. 


-Coverboard wise they have the Soundproof plasterboard-a lovely lilac colour so would need some paint but a good option. Also a 9mm plasterboard with 12mm polystyrene on the back for £16.68. Don't believe the plasterboard on this one is so soundproof though and it also raises the question of do I fill the other inch behind the polystyrene in with something or not. = More money.

Otherwise OSB, MDF etc that looks OK, I guess it does have the plus that it is easier to screw into than the plasterboard but would possibly still have to paint. Doesn't have sound properties of the plaster.


So those are my notes so far, probably leaning to either the Space loft stuff, or just plain polystyrene.

I didn't look for the vapour barrier, would this go between insulation and coverboard?

Also, should I be thinking about doing the same for the floor? Unless it fouls the door obviously. Or something different? I guess the same question also goes for the door, which I guess needs doing.

Thanks for everyones help


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## galwayworker

Hi Fraser,

It can be very confusing when looking at insulation products and how effective they are. The three types of insulation products that you are looking at are basically

a)	Celotex Insulation; this is a polyisocyanurate (PIR) board product. PIR is considerd to be one of the most thermally efficient insulation boards and as such is one of the most expensive.
b)	Polystyrene Insulation; this is the traditional white insulation board. In terms of thermal efficiency it’s pretty good.
c)	Fibreglass Quilt / Rockwool; usually laid in attic spaces or timber framed houses, it needs to be fairly thick to achieve the required thermal performance. If you only have 50mm of space for the insulation then squashing 100mm into this space will only achieve the equivallent of 50mm insulation.

A quick basic calculation of u-values for the wall with 22mm board on the outside, 50mm studs, insulation between studs, vapour barrier and 6mm ply on the inside.

PIR insulation; u-value of 0.36 W/m²k 
Polystyrene insulation; u-value of 0.53 W/m²k	
Fibreglass insulation; u-value of 0.85 W/m²k

So the PIR is the best performaing insulation followed by polystyrene and then fibregalss. I went for polystyrene in my shed (50mm) and it heats up quicky with a small heater and hold the heat well.

I hope this hasn’t confused the issue further


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## foxhunter

If you have a Champions Timber depot near you take a look at their Sheet Materials book. It is very useful and gives the various properties of insulating etc materials.


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## fraser

Foxhunter, I don't but thanks very much anyway. We don't have much choice on the isle of wight.

Galaway, thanks very much for taking the time to do that for me. I think looking at the maths you have done, and considering just the four walls for now, polystyrene is only £30 more expensive than the loft insulation and probably represents better value for money. Plus the ease of fit. I will probably also use this on the floor and roof though for this weekend, that will keep me busy. The celotex/recticell is just too expensive for me at the moment.

I think I will be covering it with 9 or 12mm shuttering ply, probably 9, then paint.

I do have concerns about a vapor barrier, just as perhaps polythene, which I can get through work. If I use this between the exterior shed walls and the polystyrene, will the polythene not gather moisture, thus making the insulation wet? A couple of people have said to use it but I'm not too sure how it works?


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## fraser

As I understand, this is the order in which this should be done

Cladding
Breathable membrane stapled to the cladding and inside edges of the joists
2" polystyrene or 100mm loft insulation
Polythene stapled to face of joist over insulation as vapour barrier
9mm shuttering ply

Is this correct? I am a bit concerned that the membrane and vapor barriers will be sat against the insulation and interior and exterior walls. If they get wet which i guess they will if they are acting as a barrier, surely everything else will get wet?


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## Dee J

With a fairly impermeable insulation like polystyrene a vapour barrier is less of an issue. But if you fit a vapour barrier (aka polythene) make sure it's on the warm side of the insulation. In this situation, breather membrane is a bit OTT.

Dee


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## galwayworker

I agree with Dee on the vapour barrier. 

If it was a domestic setting where you are trying to maintain a constant level of heating (say 16 degrees) then the risk of condensation would require a vapour barrier. In a shed that is only going to be heated for two or three hours every few days then I don't think the risk of condensation is very high. Polystyrene is waterproof and I don’t think it's thermal performance is affected if it gets wet. The problem of installing a vapour barrier is that it needs to be airtight when you are finished. All the joints and where it has been stapled to the studs have to be taped up to ensure this airtight finish (including where it meets the floor and ceiling). In a timber frame house it’s a right PITA to do it… so in a shed I don't think the barrier will stay airtight very long (fixing shelves etc to the wall).

I would keep it simple, 50mm polystyrene and your ply.


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## MickCheese

As I understand it and how I have done it in the past.

Starting from the outside - Shiplap, (the last two sheds had a sort of tar paper, don't know what it is called) then the insulation, vapour barrier, plasterboard / ply or whatever.

Mick


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## decas

If you are still interested in panel insulation then you might add these guys to your list. I have had Kingspan seconds from them in the past and they gave good prices and service. They will give advice if you ring them up. Good delivery service. Look under the special offers on the website - what is available changes all the time depending on what they get from suppliers.

This is my first post so it won't let me post you a link so put secondsandco into Google.

Dave


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## fraser

Hi guys
Having put the insulation in and paneled over it a few weeks back, I have finally managed to get back in the shed to give it a lick of paint. I thought I would be nosey and see if there was any condensation between the shed and the visqueen vapour barrier on the ceiling so took a panel down to have a look. It is wet...it hasn't got through to the insulation but there must be water getting in (through the felt?) somewhere and stopping on the visqueen, creating some small puddles. The joists and roof are therefore wet.
What can I do about this? I thought it was pretty water tight but clearly not, or could this be water in the air and something I really cannot do anything about? I havent looked at the walls yet, not sure if I can bring myself to do it! 
Any help would be really great
John


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## fraser

Just to add, I have only actually insulated half the ceiling so far and the joists on the half without the insulation, are dry.
Could it be that the visqueen is inviting the water from the air to sit there. It is not condensation from my breath as I have not been in the shed since I did this, which was a few weeks back, and it is the wrong side of the visqueen for that anyway.


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## foxhunter

Just a thought from someone who knows nothing about anything!

I remember on a thread some time ago from a guy who has now left the forum it was mentioned that it is important that the vapour barrier is fixed on the inside of the insulation - OR IS IT THE OUTSIDE!


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## jack55

Hi when I did mine I put a waterproof breathable membrane on the outside then the cladding. Then on the inside stuff the walls with cheapo loft insulation, followed by a vapour barrier covered over with 6mm OSB. The floor has 18mm chipboard T&G 2" polystyrene and another layer of 18mm chipboard T&G. Its nice and warm in winter and cool in summer.


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## fraser

Will that not still attract condensation to sit on the barrier and make the ply wet rather than the roof?


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## jack55

fraser":2zh68esc said:


> Will that not still attract condensation to sit on the barrier and make the ply wet rather than the roof?



the barrier is breathable and you ideally leave an air gap between it and the outer layer.
the barrier is on the outside then the cladding, here the batterns allow an inch air gap between the barrier and the cladding.












Inside the walls are insulated






Then a vapour barrier





The roof is the same

Insulation in this case 4" polystyrene then a breathable barrier then boarding then felt then roofing material.











Between the insulation and the barrier is a 50mm air gap vented at the eaves


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## chaletview

I have an 18' x 15' shed with a 1 meter high apex roof.
I have had it about 5 years and would now like to turn it into a studio of sorts.
I have read all the previous posts and have created a chart which encompasses the essence of what a number of you have suggested.
Does my interpretation seem reasonable?

My main lack of understanding is condensation.

I would welcome anyone's views on this.

Thank you

PS I would have preferred to show the diagram in the main body of the text but couldn't work out how to do this. Sorry.


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## Dibs-h

A few things -

1. I wouldn't use polystyrene. Whilst it it is better than nothing, if it catches fire - screwed is putting it politely.
2. I would rather line with ply - it adds some rigidity and all importantly security. & no VOC's or whatever mdf gives off. and should you have a leak (water penetration), ply is far more tolerant.

HIH

Dibs


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## Lons

m1ke_a":1spnadzw said:


> Think of the Roc slab as dense firm loft insulation. It isn't solid but has definite shape and form which means you can install it vertically in wall voids etc. IIRC I got mine from Jewsons about 6 years ago.



All the builders merchants stock it but what you should ask for are "cavity wall bats". they are available in several thicknesses to suit the internal gap of a cavity wall, are sold in packs of several M2 9dependant on thickness. (just done a quick google and this is the first linlk http://just-insulation.com/rockwoolcavity.html ). I buy mine from Jewsons.

They are more expensive than loft insulation but made to withstand moisture, have more sound absorbing properties and are self supporting - don't sag.

Cellotex type sheet is the alternative but more expensive. Even easier to handle just mind the dust when you cut it - even with a knife - plays havoc with my eyes :roll: 

Bob

EDIT...... NOTE TO SELF - READ ALL THE PAGES NOT JUST THE FIRST ONE BEFORE POSTING YOU D******D


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## MARK.B.

No expert Chaletview but would it be wise to glue the tarpaper to the shiplap ?,any movement in the wood could potentially tear it.Maybe put a layer of ply/osb and put the shiplap on that (10mm thick shiplap imho may not be strong enough).


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## billybuntus

I've used 100mm cheap loft insulation stuffed into a 75mm void with a heavy poly sheet over it as a vapour membrane (non breathable. Lined out with 1/2 inch mdf as it was free (coated the mdf in clear would preservative then painted with white undercoat).

No problems with it at all and it keeps the heat in immensely well.


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## giantbeat

i am using wicked general purpose insulation slabs in the roof on my workshop, decent thermal insulation & noise reduction, currently on offer @ £26.69 a pack which covers 7.2m2 which came up good value from what else i had found, the fact that is literally a 30 second walk for me also sealed the deal.


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## chaletview

Many thanks for getting back to me. I assume the rest of my chart is OK?


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## chaletview

I drew up the diagram as I had read through all the previous posts.
As some of them are old I just wanted to check if this was the current way of insulating a large shed.
Thanks to giantbeat and billybuntus and MARK.B. for your helpful replies.
As a newcomer I appreciate the hand holding.


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## chaletview

Hello GIANTBEAT, if the gap is 70mm deep, should I get filler to fit in exactly or leave a gap?


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## buffalobill

chaletview":2vnrv01q said:


> Hello GIANTBEAT, if the gap is 70mm deep, should I get filler to fit in exactly or leave a gap?


You should fill it , should not be a gap between the insulation and the vaporbarrier.
Rockwool and others have many diffrent 50,70-100,150 and thinner and thicker


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## beech1948

chaletview,

You got it almost right. The structure of the walls should be :-

0) Seal up all small gaps in the structure
1) Outer cladding...NO tarpaper against it at all
2) 25mm air gap. Achieved by putting roof tile laths or similar nailed down the studs and then later nailing the cladding across these
3) Breathable outer membrane eg Tyvek wrapped around the stud frame
4) Insulation of choice
5) Vapour barrier with all edges and overlaps taped up and together to form an impervious barrier including taping over all staples or nails
6) An internal wall layer which could be plasterboard, ply or OSB. OSB is about 60%+ resin glue and could be regarded as a solid barrier. It can be painted white easily and is cheap.

Now your construction did not follow this as you initially missed out on the external air gap and the breathable membrane and maybe you did not close up all of the small gaps.

I don't know where the water is coming from in your roof but finding that leak and closing it seems like a first step.

I assume you have felted the roof. I am less than certain that felt is good enough for a workshop. You may want to cover this over with say ONDULINE with use of the eves and roof ridge panels to provide a solid and waterproof roof. Onduliner is easily available and fairly cheap. Its a panel made from bitumen like resinous layers and has a wavy appearance. 

Having dealt with the roof you may want to stop there and see if you have any other leaks from the walls...if it seems OK then enjoy.

All of this was discussed many times a few years ago but as a newcomer you may have missed these posts. Search for Mike Garnham
and workshop builds as he was the undoubted master of workshop construction.

Hope this helps

Al


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## chaletview

Thank you beech1948 for your comprehensive reply.
Just to be sure can I just mention that I have a large shed 18' x 15' which has been in situ for 5 years or so and in good condition.
I now want to insulate it. It does not leak.
The key features are that the construction is of 10mm thick shiplap X 120mm wide - again all in very good condition.
The stud frame is 70mm deep by 35mm wide. The gaps between the uprights is 560mm in the main.
I was thinking of buying the thermal insulation & noise reduction, currently on offer £26.69 a pack which covers 7.2m2 from Wickes suggested by giantbeat.
However that is 50mm thick so arguably there would be a gap of 20mm. Should I go for 75mm thick and will it 'stand up' between the uprights.
How should I attach the insulation to the inside of the shiplap?


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## giantbeat

chaletview":32e9wxo8 said:


> Thank you beech1948 for your comprehensive reply.
> Just to be sure can I just mention that I have a large shed 18' x 15' which has been in situ for 5 years or so and in good condition.
> I now want to insulate it. It does not leak.
> The key features are that the construction is of 10mm thick shiplap X 120mm wide - again all in very good condition.
> The stud frame is 70mm deep by 35mm wide. The gaps between the uprights is 560mm in the main.
> I was thinking of buying the thermal insulation & noise reduction, currently on offer £26.69 a pack which covers 7.2m2 from Wickes suggested by giantbeat.
> However that is 50mm thick so arguably there would be a gap of 20mm. Should I go for 75mm thick and will it 'stand up' between the uprights.
> How should I attach the insulation to the inside of the shiplap?




you should not need to attach the inuslation to the shiplap matey, you can cut the insulation sightly larger than the gap between the studs & push fit in so its wedged in place.

i have never insulated a shed but am insulating my cellar ceiling, I'm just cutting the insulation 2-3cm wider than i need & pushing it in place, it compresses uneasily & holds its self in place very solidly.

You should have no issue doing what you are wanting, the instructions for fitting it between studs are on the insulation instructions, if you read the reviews from the wicked site people have used it for all sorts of things.


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## beech1948

chaletview":2q8w2a5h said:


> Thank you beech1948 for your comprehensive reply.
> Just to be sure can I just mention that I have a large shed 18' x 15' which has been in situ for 5 years or so and in good condition.
> I now want to insulate it. It does not leak.
> The key features are that the construction is of 10mm thick shiplap X 120mm wide - again all in very good condition.
> The stud frame is 70mm deep by 35mm wide. The gaps between the uprights is 560mm in the main.
> I was thinking of buying the thermal insulation & noise reduction, currently on offer £26.69 a pack which covers 7.2m2 from Wickes suggested by giantbeat.
> However that is 50mm thick so arguably there would be a gap of 20mm. Should I go for 75mm thick and will it 'stand up' between the uprights.
> How should I attach the insulation to the inside of the shiplap?




I'm not an expert on insulation more a follower of Mike G's recommendations.

I would suggest that you use the batts of stiff insulation mean for brick cavity walls as these come in easy to handle sizes are fairly easy to cut.

I wouldn't attach to the cladding at all

I might consider adding a breathable membrane to the inside but I don't know for sure that this would work because they usually need the air gap to work best.

You could just use 2inch batts and place a lath between the batts and the cladding to act as a spacer and to give an air gap of 20mm.

Filling any and all gaps would be good to achieve with a foam gun is what I usually use.

Inner impervious membrane all taped up and then an outer wall covering of say OSB.

regards
Alan


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## chaletview

Many thanks to you all for your helpful suggestions.
I will digest this at the week-end and plan the installation.

I really am very grateful.


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## will1983

Chaletview, how did you get on? and did you take any photographs?


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## Walnutt

Hi, I'm new here but this thread has been of real interest.

I'm getting a 12x8 timber pent shed delivered on Tuesday for a general woodwork workshop and have the insulation lined up as per Beech1948's recommendations, hoping to have minimal damp / condensation.

Process is, from the outer to the inner..

13mm shiplap t and g (All studding frame gaps sealed).
25 mm air gap (with breather vents in each stud section top and bottom).
Breathable membrane.
Kingspan 43mm (seconds..).
Polythene vapor barrier taped (warm side of insulation).
11mm osb3.

Roof is vented at front and back and the same process is adopted but with 50mm air gap.

Shed has 3x2 bearers on paving flags and floor is 1" tantalized and I am thinking of adding a suspended OSB3 18mm with 23mm king span as follows from floor upwards.

1" tantalized floor
20mm air gap
23mm kingspan
18mm OSB3.
No ventilation in the sub floor sections....

I've read the Mike Garner posts / links and found them really useful. I'll be using stainless insect mesh to protect the air gap sections from bugs.

Also BS 5250 for control of condensation and associated free links are useful, as is Nhbc website.

I'm ok with the sides/roof, but not sure about the floor. Anyone have any thoughts?

Thanks.


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