Insulating new wooden built garage/workshop

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Hi

I've done a search already but not quite found the answer to my specific question.

Basically i'm building a new wooden garage\workshop from scratch. The walls are going to be made from 2"x4" and clad in waney edge\featheredge boards. I'd like to insulate it properly as i'll be spending quite a bit of time in there so my question is would it be wise to wrap the whole stud wall frame in some sort of breathable membrane first before before cladding the outside?

then with regards to insultating it after that i was going to fill the wall cavities with 600mm wide glass cavity slabs then ply board the inner walls.

Does that sound like it will work or is there some other vapour barrier aspect i need to take into account?

Also there will be a gap (at present due to the current design) to the outside where the roof trusses meet the top of the wall frames. Does this gap need closing/insulating or is this needed for air to circulate?

Any help very much appreciated as is any recommended brands of products or exact specs of materials i need to ask for at my local builders merchants

cheers

Matt
 
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Hi

Basically i'm building a new wooden garage\workshop from scratch. The walls are going to be made from 2"x4" and clad in waney edge\featheredge boards. I'd like to insulate it properly as i'll be spending quite a bit of time in there so my question is would it be wise to wrap the whole stud wall frame in some sort of breathable membrane first before before cladding the outside?

then with regards to insultating it after that i was going to fill the wall cavities with 600mm wide glass cavity slabs then ply board the inner walls.

Does that sound like it will work or is there some other vapour barrier aspect i need to take into account?
Yep will work. You should affix 25mm batten to the 4x2's over the breather membrane to allow air circulation and ingress run off behind the cladding.
You will need to fix polythene vapour barrier to the inside studs before plyboarding. Airtight and taped up.

Also there will be a gap (at present due to the current design) to the outside where the roof trusses meet the top of the wall frames. Does this gap need closing/insulating or is this needed for air to circulate?


Matt

You will need some ventilation in the room itself, best to fix airbricks at floor level or adjustable wall vents either end.

No point in insulating walls if you ignore the roof, best would be continuous insulation from the top of walls to the roof. You should then crossbatten the roof joists (on top of the insulation) with 2x2's and put the roof boarding over this. The spaces between the 2x2 should be vented to the outside (so the underside of the roof deck gets a change of air) and covered with steel mesh or fit soffit vents.

You could also do a warm roof, but bit trickier to get continuous insulation. (google/forum search)

A roof window facing south will bring extra light and keep the temps inside slightly warmer during cold spells. (and vice versa)

Rockwool is fairly cheap in bulk from merchants and also will provide a degree of soundproofing to reduce annoyance to the neighbours if you are using power tools in there.
Foil backed kingspan type insulation much better at insulating, but pricey for a shed and no sound dampening properties.

Whatever you do, get a couple of courses of brickwork with a roll of dpc atop, to sit the structure on to.
 
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That's brilliant!!!

thanks ever so much for your detailed reply!!

I'll be sure to update once i get to the wall stage

Cheers

Matt
 
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I've got another couple of questions I'm hoping you might be able to help with :)

with regards to the roof insulation do i take it that its the same method as the walls ie I'd need a breathable membrane covering the roof over the roof boards before i fit the felt shingles and then on the inside i'd cover the insulation again with a polythene membrane? or is it just fine to have
shingles > roof board> insulation> separation battens >internal ply cladding

also with regards to the polythene membranes you mentioned getting them air tight, this is probably a stupid question but how do you attach the membrane to the stud wall to enure airtightness? do you use some sort of sealant/adhesive or can a staple gun be used?

thanks again
 
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