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Minimising heatloss with steel lintels

RogerS

RogerS

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We have a 4.7m steel spanning where the sliding doors will go. There is an inside steel that supports the joists and sits on top of masonry piers etc. There is also an outer steel that will take the sandstone lintel as part of the surround.



To maximise the amount of sandstone visible outside on the jambs, the builder was suggesting overlapping the steels..ie locating the inner steel inside the outer one so that the outer steel can slide further back towards the inside of the house. This would mean that the doors would sit further back in and so reveal more of the jambs.

I've resisted this saying that that will effectively cold-bridge along the span, condensation on the inside wall and heat loss. Is that a fair comment ? Gut feel suggests that the two steels should not be touching.

What else though to minimise heatloss there? Bung some Kingspan in between them? Where the arrow is.
 
Offset the height of one to the other by 20-30mm, slide one inside the other by 50-60% then fill the cavity with expanding foam…?

Cheers
Mark
 
Yes, Roger, you're right, and he is wrong. They shouldn't touch or you will have a nasty cold-bridge situation. You should make sure you have as much high-quality insulation in there as possible, and the best way of achieving this is to put the first one up, then pack it with insulation before you put the second one up. Ideally you'd want a 50 or 75mm gap.
 
Rod":1oxs7jxz said:
Are you having the beams specially manufactured- they one with the wider web looks unusual?

Rod
Click to expand...

Manufactured on site! Well, sort of. Got an extra length of flat steel stock and the guys welded it on to the bottom web...very neat welding as well to my untutored eyes. Then Red Oxide or whatever on it.

I got them to cut off the rear webs so the steel could sit further back into the void thus exposing more of the very nice stonework that he's done for me.

It very nearly all went horribly wrong late last night. I was on my own and took another look at the spacing between the two steels and thought that they were too close and that I could lift up one end of the outer steel with an Acrow prop and nudge it out a little - even though I'd lose a little visible stonework. Well, it's tricky holding an Acrow in one hand and trying to turn the rusty sleeve with the other when all of a sudden the steel came off the pad and started to swing out towards me and down to the ground. Luckily, it hadn't got too much momentum and so was able to bring it back under control.

I have many tins of foam to squirt in the gap. There is some kingspan in the inner web but none in the outer steel due to cutting off the webs.
 
Need to ensure any rain water running down the outside wall does not run across the foam etc and back into the building. Mike should be able to help here with the detailing.

Mark
 
meccarroll":3i2r6v4x said:
Need to ensure any rain water running down the outside wall does not run across the foam etc and back into the building. Mike should be able to help here with the detailing.

Mark
Click to expand...

Good advice, thanks, Mark but fortunately for me these steels are tucked up underneath the eaves and so not likely to get any water ingress. (Famous last words)
 
meccarroll":1g5ju8u7 said:
Need to ensure any rain water running down the outside wall does not run across the foam etc and back into the building. Mike should be able to help here with the detailing.

Mark
Click to expand...

Sorry, I'm not following. The foam is between the steel, so any water that gets that far is already inside your building. Am I missing something?
 
Mike G":25jorzfc said:
meccarroll":25jorzfc said:
Need to ensure any rain water running down the outside wall does not run across the foam etc and back into the building. Mike should be able to help here with the detailing.

Mark
Click to expand...

Sorry, I'm not following. The foam is between the steel, so any water that gets that far is already inside your building. Am I missing something?
Click to expand...

No, I don't think so. I think that Mark was possibly thinking that the doors were set into a two-storey wall.
 
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