Insulating a gable end steel frame.

[RichD1]

Just getting things ready for the plasterers to come in and plaster the room around the steel A frame forming the gable end. The drawings state a double layer of plasterboard but is that enough to prevent cold faces all around the gable end window?

I've already glued in wood noggins in the steel webs to take the plasterboard screws, but should I insulate in the web and is this worthwhile as the steel forms the reveals both sides and over the top and can only take two layers of plasterboard.

 

[robinbanks]

The drawings state a double layer of plasterboard but is that enough to prevent cold faces all around the gable end window?

No; plasterboard alone is not innately an insulating material

but should I insulate in the web and is this worthwhile

Unlikely that adding insulation to the web will cure the cold bridge but it may help reduce the cold surface area presented to the room

as the steel forms the reveals both sides and over the top and can only take two layers of plasterboard.

This cold bridge should have been better designed out at the start. I'd be looking to put the steel entirely in the cold side and insulate the room from it completely

Upload pictures of what you have now and of any drawings, so we can better advise

 

[freddiemercurystwin]

Nothing to add here until the OP supplies some answers ......

 

[RichD1]

I’ll take some photos tomorrow.

 

[RichD1]

This is what the gable end of the steel frame looks like.

I've now padded out all of the steel webs with rockwool and the drawings states two layers of plasterboard over any exposed steel. The underside of the cross beam between the top and bottom gable window will have 50mm insulated plasterboard. The cavity side of the steels have cavity batts behind the brickwork and more rockwool in the web of the crossbeam and the outer window facia. Any small gaps will be foamed.

I think that is as much as can be done.

 

[baker332]

Can you not use celotex in the webs? Like you've done on the bottom left of the picture?

I think not a lot more can be achieved here, sometimes BC need to accept and be pragmatic around the solution presented.

 

[robinbanks]

sometimes BC need to accept and be pragmatic

Why? If something's been designed wrong from the start, why should BC accept it just because noone called out that it was silly at any point between then and now? That's like pouring foundations for a 3 storey house out of 150mm C10, building the first storey and then saying "well, BC just have to accept that it is how it is and be pragmatic, cos there's a wall built on it now"

I think that is as much as can be done.

I'd ditch all the timber down the sides and replace it with insulation, keeping just a few small bits for where your window strappings fix through, and wrap that entire set of steelwork in 50mm+ of PIR, get it out to the cold side

Are you adhering insulated PB to the block walls?

 

[baker332]

Why? If something's been designed wrong from the start, why should BC accept it just because noone called out that it was silly at any point between then and now? That's like pouring foundations for a 3 storey house out of 150mm C10, building the first storey and then saying "well, BC just have to accept that it is how it is and be pragmatic, cos there's a wall built on it now"


I'd ditch all the timber down the sides and replace it with insulation, keeping just a few small bits for where your window strappings fix through, and wrap that entire set of steelwork in 50mm

Are you adhering insulated PB to the block walls?

You're talking about extreme cases, I am discussing the one at hand. Insulate with celotex.

 

[robinbanks]

You are, but youre talking about putting it in the webs, which is only half the story, really. There is enough space here to get some PIR in where just plasterboard is being proposed, and I think that opportunity should be leveraged; it seems mostly possible to clad the entire room-side presentation of this steel in insulation

RichD1 have you got the enginner's drawings available?

Also, how come the ceilig is skimmed when the walls aren't even plasterboarded? Such an odd detail

 

[RichD1]

No engineering drawings for this detail. Just very loose statements of two layers of plasterboard around exposed steel for fire purposes.

I started with PIR padding but it provided difficult. The steels had lots of tek bolts in the webs to secure wall ties in the side and back faces and holding the timber linings which prevented the PIR being fitted easily. So I've padded with Rockwool. I also had the Plasterers on my back waiting to board.

I've now got 50mm PIR insulated plasterboard around all the steel faces.

The ceiling was skimmed first because we had an internal scaffold frame the length of the room to reach the vaulted ceiling and the veluxs. This was removed and then walls lined and skimmed. No problem as the finish and join is superb.

 

[robinbanks]

Ref the difficulty in PIR'ing a load of screws etc I've always wanted to give this a go:

PENOSIL 12 cans of Easy Spray Foam, 1 x Foam Applicator Gun, 1 x can of Gun & Foam Cleaner - Bundle Package

PENOSIL EasySpray is an environmentally friendly insulation foam with a special spray applicator for the gun tip. Spraying allows for insulating uneven or curved substrates and hard-to-reach places with a smooth even layer of foam. Helps to reduce thermal bridges and prevent condensation. HIGH...

www.abbuildingproducts.co.uk

It looks like typical expanding foam but it's actually more like like the foam that gets bad rep for being sprayed on the underside of tile/slate roofs

I've used its bigger brother, the two part canisters:

Froth-Pak QR 600 Spray Foam Kit

Froth-Pak 600 QR Kit is a two-component closed-cell polyurethane spray foam system that comes in 2 disposable pressurized containers requiring no external power source. It is used as a foamed-in-place insulating air barrier sealant for insulation and air leakage control in the building envelope...

www.abbuildingproducts.co.uk

And also the two part liquid you mix yourself and wait for it to go wild and turn into kingspan..

CFS Fibreglass - 2 Part Polyurethane Foam Part A & Part B 50kg kit - GRP Supplies

2 Part Polyurethane Foam Part A & Part B 50kg kit

www.cfsnet.co.uk

..both awesome products that create beautifully structured closed cell insulated layers on whatever you coat them with.. streets ahead of typical expanding foam.

But they're expensive and not really something you stop and start with; you just get a long list of everything that needs spraying and gun the lot or you struggle to use the liquid two part because of gravity

The smaller cans seem to have similar constraints as expanding foam, can't lay it on too thick, but a lot more controllable and easy stopnstart due to portion size ..