Shed door - airtight and insulated?

[Glitch]

I'm a noob so bear with me. (I did put this on another forum but struggling for any response)

I've built a forever shed/micro 'shop/shack combo at the end of my garden. One-off retirement project. Planning to get a small workbench in the 2.5m x 2.5m' shed interior.

Shack is for all year round BBQ (another obsession).

Over engineered, over budget, over thought, over time. Some things I'd change if I did it again. Wish I'd found this site before I started.

It is built in C24 4x2, 16" on centre frames. 11mm OSB sheathing, outside and in. Tyvec wrapped outside, EPDM roof(s), Vapour control layer inside with 11mm OSB finish. 75mm sheep's wool insulation. Ordered Siberian Larch T&G for cladding, B grade for back and sides. 20amp power supply (couldn't get cable to the CU for its own circuit)






Anyway, I'm agonising over the door. Having Insulated and sealed the internal walls the door is likely to be the weakest link.

Luckily a neighbour is a professional joiner and he has kindly offered to do the mortice and tenon joints for the frame. I know I should have a crack at it myself but other than going to a local public workshop I don't have anywhere to do it, yet.

I'm thinking framed, ledged and braced with vertical larch T&G to match my OTT spec..

However, given all the layers I've added and the thickness of the insulated/lined/battened/clad walls do I just make it as draughtproof as I can and accept the heat loss and gaps? Or is there a way to insulate and draughtproof without covering up a nicely framed door.

Also, door opening is only 790mm (same as my house internal doors) but didn't think about door jamb/liner .

Presumable best to line the opening for cleaner finish but lose more off an already narrow door?

 

[Mike G]

Hi and welcome.

That looks a lovely little workshop. I'm sure you'll really enjoy the space. It's a pity you have lined the outside of the frame with OSB, as that is effectively a vapour barrier on the wrong side of the insulation, but it's too late to do anything about that now, I guess.

As to your question..... Personally I wouldn't (and didn't) bother. If you seal up the door you will likely need to install some ventilation elsewhere. I have gaps around my uninsulated doors, and whilst it means I need a little more heating when using my workshop, it does mean that I don't get any condensation (and thus rusting) issues.

Lining the opening is an issue only if it would otherwise leave some insulation exposed. I suspect it won't do that, so hinge your doors directly to the studs, and just plant a stop. I would find such a narrow door an endless frustration, but I guess you won't be building big pieces of furniture in your workshop.

 

[Malc2098]

Hi and welcome.

I've recently made a permanent pair of doors form my 'shop, ledge, brace and batten from local larch. Hitherto, they were 18mm OSB with 50x25 reinforcement around edges and hinge braces. Given the all the other insulation I installed in the build, I didn't insulate the doors ( and I can see daylight in some of the gaps! ) and the shop hasn't fallen below 5 degrees inside since I completed it. It warms nicely from an oil filler radiator/convector.

I'm not going to insulate the new doors now a) because I like the look of them, and b) the exposed wood is good to hang stuff on.

My new doors will hang my steps, my apron, the spare hose for the small dust extractor, the stand for my phone (high enough to pick up the wifi signal from the house and maybe other and sods.

The other pair of long term temporary OSB doors which are only for machine access, have numerous clamps attached to the framework and the workshop broom!

 

[Glitch]

Hi and welcome.

That looks a lovely little workshop. I'm sure you'll really enjoy the space. It's a pity you have lined the outside of the frame with OSB, as that is effectively a vapour barrier on the wrong side of the insulation, but it's too late to do anything about that now, I guess.

As to your question..... Personally I wouldn't (and didn't) bother. If you seal up the door you will likely need to install some ventilation elsewhere. I have gaps around my uninsulated doors, and whilst it means I need a little more heating when using my workshop, it does mean that I don't get any condensation (and thus rusting) issues.

Lining the opening is an issue only if it would otherwise leave some insulation exposed. I suspect it won't do that, so hinge your doors directly to the studs, and just plant a stop. I would find such a narrow door an endless frustration, but I guess you won't be building big pieces of furniture in your workshop.

Thanks Mike, much appreciated.

Re: the external sheathing. I know I've gone OTT in places. So many layers!
I've copied others I've seen (sadly, not yours).

Basic principle was getting the outside weatherproofed with OSB and breathable, waterproof Tyvec wrap. Then cladding for appearance rather than primary weatherproofing - (decided before I chose the cladding)

I've not seen building wrap over insulation without external sheathing before, but I clearly haven't looked hard enough.

Vapour control as I understand it is an airtight layer on the inside of the insulation to stop moisture passing into the fabric of the structure.

I read one of your posts where you say OSB is a vapour control layer. I have assumed it isn't. I think moisture can pass through it. You need expansion gaps which surely compromise the barrier.

Cold roofs are particularly liable to condensation/mould/rot so I was keen to get a VCL and make sure there is free flow of air between the rafters.

BTW I grown to dislike OSB. It's nothing more than compressed Weetabix and if left in milk for long enough would probably make a good high fibre breakfast

The latest batch of 11mm OSB3 I bought (from a major DIY store) has 'Internal use as a component in dry conditions' stamped on it. I think said DIY store is not describing it accurately on their website.

Anyway OSB is probably worthy of a dedicated thread.

Back to the door.
Yes, I think that's good advice and I will stick with just a decent frame and vertical T&G on the front. There's no insulation exposed. I just need a neat finish to the ends of the battens and cladding.

Yes the door opening is smallish but I don't anticipate any big furniture projects. With hindsight I'd make it bigger. Mind you, if it doesn't fit through the shed door I couldn't get it through my terraced house :lol:

Thanks again Mike. Great help and advice which you've generously shared with forum users.

 

[Glitch]

Hi and welcome.

I've recently made a permanent pair of doors form my 'shop, ledge, brace and batten from local larch. Hitherto, they were 18mm OSB with 50x25 reinforcement around edges and hinge braces. Given the all the other insulation I installed in the build, I didn't insulate the doors ( and I can see daylight in some of the gaps! ) and the shop hasn't fallen below 5 degrees inside since I completed it. It warms nicely from an oil filler radiator/convector.

I'm not going to insulate the new doors now a) because I like the look of them, and b) the exposed wood is good to hang stuff on.

My new doors will hang my steps, my apron, the spare hose for the small dust extractor, the stand for my phone (high enough to pick up the wifi signal from the house and maybe other and sods.

The other pair of long term temporary OSB doors which are only for machine access, have numerous clamps attached to the framework and the workshop broom!

Thanks Malcolm,

You and Mike have put my (overthinking) mind at rest.

I've skimmed through your shed build thread and think it's fantastic, including those doors. They deserve to be seen in all their glory. Attention to detail is amazing and sets me a very high standard to aim for.

 

[Malc2098]

Thanks Malcolm,

You and Mike have put my (overthinking) mind at rest.

I've skimmed through your shed build thread and think it's fantastic, including those doors. They deserve to be seen in all their glory. Attention to detail is amazing and sets me a very high standard to aim for.

Thanks for those kind words, G.

I am a complete novice and have just followed advice on this forum and then gone through problem solving processes as I've needed to. Just don't look too closely.

 

[Glitch]

I'm a novice too. This is probably going to be the only shed I ever build, unless the Boss says we need to move.

Retired 16 months ago so need projects like this. Mentally and physically challenging but very enjoyable when you make progress and it looks OK. Need more dry days though.

 

[Mike G]

.......Re: the external sheathing. I know I've gone OTT in places. So many layers!
I've copied others I've seen (sadly, not yours).

Basic principle was getting the outside weatherproofed with OSB and breathable......

That's the problem, you see. OSB isn't breathable. So you've placed a vapour impermeable layer on the cold side of the construction, which could lead to condensation within the wall build up as vapour from the heated interior tries to get out to the cold exterior. OTT isn't always a good thing, as in this case.

 

[Glitch]

Trying to find a positive from my error -

I've doubled up the impermeable layers on the warm side. No warm air will ever reach the cold side of the walls (crosses fingers).

I think I confused myself looking at so many shed build videos (too many U.S. ones) and never once saw one with a wrap over insulation without outer sheathing. Copied two U.K. build projects that made the same mistake as me.

 

[Mike G]

Whilst it is a big bonus that you have a serious internal vapour control layer, there is still air within the wall structure (in the insulation), and it will be warm on one side and cool on the other, inducing movement, and giving the potential for condensation to form on the inside of the outer sheathing board.

Don't worry about it overly. Your build is still better than the vast majority. But I wouldn't want anyone in years to come to read the thread and copy your wall build up when by spending less time, money, and effort they can have a better wall.

 

[Glitch]

Agreed Mike.
Your design avoids the pitfalls I have created. Adding insulation opens up a can of worms.

If I were to build again I'd leave out the outer OSB layer to facilitate the escape of water vapour to the outside.

I would add that if I did it again I still wouldn't totally trust OSB as a VCL. I would tape all the joints and consider sealing all faces and/or I would still add a suitable VCL membrane. I hope I have enough leaks in my outer sheathing to reduce the risk of a future catastrophe!

OSB has low permeability. It is not impermeable without further treatment and correct fitting. True airtight/vapourtight installation is very hard to achieve.

Your design is the best but it will allow more vapour through it than a true VCL - at least it can escape though which is the critical consideration.

Told you I overthink things (and still make mistakes) even I find myself annoying :eusa-shifty:

 

[Mike G]

Gary, you are right that OSB isn't totally vapour impermeable. However, for the sake of a simple message for people who just want to build a shed or workshop, describing it as a vapour barrier is good enough*. The important principle/ rule of thumb is that the inside of a wall build up should be approximately 5 times as vapour resistant as the outside, so that anything which does get in has a route out to where it needs to go: the void behind the rainscreen. The implication of that is that it doesn't matter if the internal layer isn't a perfect vapour barrier, in that its job is to reduce the amount of moisture getting into the wall from the heated internal air to such a level as can be allowed out by the outer face.

*You'd be amazed how often advice I give online is taken by the well-meaning and used out-of-context in giving advice to others. This means I have to keep messages simple and clear, or I have to wrap up every single thing I say in endless caveats. UKW was 2 or 3 posters who fully understand the principles and can be relied on to give decent advice in most circumstances. It has many more who get hold of the wrong end of the stick more often than not. One of the reasons I regret that I am no longer in a position to post over there is that I know there will be people receiving poor advice when asking a building question.

 

[sunnybob]

You havent reacted to MIkes comment on ventilation.
If you dont have ventilation in the shed, and you want to work in there, you should get a scuba mask and bottle. :shock: :lol:

Completely airtight is as undesirable as condensation.

 

[Glitch]

Gary, you are right that OSB isn't totally vapour impermeable. However, for the sake of a simple message for people who just want to build a shed or workshop, describing it as a vapour barrier is good enough*. The important principle/ rule of thumb is that the inside of a wall build up should be approximately 5 times as vapour resistant as the outside, so that anything which does get in has a route out to where it needs to go: the void behind the rainscreen. The implication of that is that it doesn't matter if the internal layer isn't a perfect vapour barrier, in that its job is to reduce the amount of moisture getting into the wall from the heated internal air to such a level as can be allowed out by the outer face.

*You'd be amazed how often advice I give online is taken by the well-meaning and used out-of-context in giving advice to others. This means I have to keep messages simple and clear, or I have to wrap up every single thing I say in endless caveats. UKW was 2 or 3 posters who fully understand the principles and can be relied on to give decent advice in most circumstances. It has many more who get hold of the wrong end of the stick more often than not. One of the reasons I regret that I am no longer in a position to post over there is that I know there will be people receiving poor advice when asking a building question.

Understood Mike.

Apologies - 40+ years in IT splitting hairs over designs and requirements and being precise has left it's mark. Bloody annoying .

Now I've aired it (in public) and taken it on board I can advocate your design and point out my errors.
It does make sense. I certainly don't want to confuse people. Thank-you.

 

[Glitch]

You havent reacted to MIkes comment on ventilation.
If you dont have ventilation in the shed, and you want to work in there, you should get a scuba mask and bottle. :shock: :lol:

Completely airtight is as undesirable as condensation.

Following advice from Mike and Malcolm I'm happy to have a leaky door to prevent suffocation.

Might even make it a stable door as I don't have opening windows planned at the moment.

My leaky old house might be expensive to heat but it feels healthier than a new build.

The obsession with energy efficiency house building has found its way into garden buildings :eusa-doh: .

Maybe should have gone uninsulated and found room for a small woodburner and one of those old whistling kettles. :eusa-think:

 

[Mike G]

Gary, don't fall into the trap of equating insulation with air tightness. It is perfectly possible to build an extremely well insulated house with "breathing" walls, or to build a tight modern house with high levels of insulation and yet maintain a healthy turnover of air. We don't have to have openings direct to the cold outside air to maintain a healthy interior, and one shouldn't equate fresh air with cold air. Most of my houses have a constant turnover of fresh warm air. However, we're talking about a shed here, not a house, and for an intermittently heated shed ventilation-by-draft is a reasonable compromise, where it certainly wouldn't be in any house of mine.

 

[bluebirdnick]

I have nothing helpful to say in response to your questions, but the building looks fantastic and the work looks really neat. Please do share more photos as it progresses, in particular of the cladding.

 

[Glitch]

I have nothing helpful to say in response to your questions, but the building looks fantastic and the work looks really neat. Please do share more photos as it progresses, in particular of the cladding.

Thanks but don't look too closely .
As my first and possibly only shed/shack build I'm happy with it, so far.
A few mistakes and some things I'd do differently but it'll be fine - especially when the HVAC system is retrospectively installed :eusa-liar:

Big learning curve and it certainly has kept me physically and mentally active in retirement (from a desk job).

Cladding was supposed to be 3-5 week lead time and it turned into 7 weeks, due 18th Nov.
Wife wants it painted so it'll be Sansin SDF Baltic Blue. https://sansin.co.uk/colours/ Expensive, almost extortionate but great range of colours and very easy to apply.

 

[Glitch]

Lining the opening is an issue only if it would otherwise leave some insulation exposed. I suspect it won't do that, so hinge your doors directly to the studs, and just plant a stop. I would find such a narrow door an endless frustration, but I guess you won't be building big pieces of furniture in your workshop.

Trying to get my head around the door fitting and the finished look.

If I hinge on the studs the door will not be flush with the cladding and stop the door opening beyond 90 degrees.
I have 11mm OSB + 25mm batten + 21mm cladding = 57mm projecting from the frame.

Will parliament/projection hinges solve the problem? It will need a thick frame - 0ver 36mm to have a stop inside the frame.

Or should I frame the door opening with 57mm thick timber to bring it flush with cladding. Also gives a neat finish to the cladding/battens/OSB?

 

[Mike G]

Your choice, Gary.

Is it too late to widen the opening?

 

[Glitch]

Your choice, Gary.

Is it too late to widen the opening?

I think it's too late Mike.

I'd surely end up compromising the integrity of the framework by cutting into the jack studs that support the header above the door. Not that that wall is taking the brunt of the roof weight - that's on the side walls.
There'd be a fair amount of dismantling now with a danger of me making it worse.

I should have made the door wider and accommodated a decent liner. As I mentioned earlier I live in a terraced house and all materials/furniture has to come through an internal door that is the same size as the shed door. Plus it's a very small space anyway so nothing major is going to be made.

 

[Mike G]

Gary, in the UK there is no such element of a timber frame as a "header". It's a lintel.

You are probably going to end up with parliament hinges and a bumped up door edge on which to fix it.

 

[Woodbloke]

I should have made the door wider and accommodated a decent liner. As I mentioned earlier I live in a terraced house and all materials/furniture has to come through an internal door that is the same size as the shed door. Plus it's a very small space anyway so nothing major is going to be made.

You seem to be worried about the width of your 'shop door; I wouldn't be



My shop 'door measures 790mm and all the workshop gear has gone through it (huge industrial bandsaw, cast iron table saw, very heavy work bench, router table, Jet 260 pt etc and massive chunks of wood which you can just see in the rh corner. In addition, everything I've ever made in there in the last 17 years or so has come out through it; several large display cabinets, a huge :shock: Korean style chest of drawers, a media unit for the TV etc. A single door width is amply wide enough in my view for most domestic projects and I seem to recollect that when we ditched our old enormous leather DFS sofa thingie 18 months ago for something a little more 'chic' :eusa-whistle: that too disappeared out into the road via an internal door in the lounge and thence the front door - Rob

 

[Glitch]

Gary, in the UK there is no such element of a timber frame as a "header". It's a lintel.

You are probably going to end up with parliament hinges and a bumped up door edge on which to fix it.

I thought lintels were things you put in soups and curries. :eusa-doh:

I'll set up a prototype for the hinge set up like Malcolm did with his. Hopefully work out the best solution.

 

[Glitch]

You seem to be worried about the width of your 'shop door; I wouldn't be

My shop 'door measures 790mm and all the workshop gear has gone through it (huge industrial bandsaw, cast iron table saw, very heavy work bench, router table, Jet 260 pt etc and massive chunks of wood which you can just see in the rh corner. In addition, everything I've ever made in there in the last 17 years or so has come out through it; several large display cabinets, a huge :shock: Korean style chest of drawers, a media unit for the TV etc. A single door width is amply wide enough in my view for most domestic projects and I seem to recollect that when we ditched our old enormous leather DFS sofa thingie 18 months ago for something a little more 'chic' :eusa-whistle: that too disappeared out into the road via an internal door in the lounge and thence the front door - Rob

Only worried about it ending up smaller than the 790mm internal door in the house. I didn't factor in the liner. I'm sure it is going to be fine but I certainly could have made it easier for myself!