ectoplasmosis Posted February 4 Share Posted February 4 We are having an extension built using a ‘goalpost’ steel support structure, with steel columns resting on the he concrete footings. The steels have already been installed, without any kind of thermal break material under the columns; they are resting on concrete pads and will penetrate through the floor slab, insulation and screed with UFH. We planned to leave the steels exposed, as a feature. We are wankers, I know. Aside from putting a 50mm PIR barrier around the base of the steel posts to separate the UFH screed from them, there’s not much else that can be done now. Are we in for a world of hurt? How bad will the thermal bridge to the footings really be? The rest of the steels will be within the thermal envelope. We aren’t building a passive house; this is an extension on the back of a solid-walled Victorian house, but we’re fitting ASHP, MVHR, EWI/IWI to most walls etc, so this thermal bridge oversight is keeping me up at night… Link to comment Share on other sites More sharing options...
Gus Potter Posted February 4 Share Posted February 4 35 minutes ago, ectoplasmosis said: Are we in for a world of hurt? How bad will the thermal bridge to the footings really be? Not a lot, probably less than the door / window handles and the letter box on the front door. Forget it and move on. 1 Link to comment Share on other sites More sharing options...
saveasteading Posted February 5 Share Posted February 5 Every column in the world is sitting on concrete. Yes, you lose heat that way so you accept that or insulate the steel. The only other option is to insulate the outer faces of the foundation. I don't. Link to comment Share on other sites More sharing options...
Russell griffiths Posted February 5 Share Posted February 5 Forget the footings, how are you separating it from the cavity or the outside. don’t have it on show it will look shit, it’s not an old 1860 factory your converting. insulate it then board it. I was going to have a huge steel in the ceiling exposed, was even looking for fake rivet heads to glue on, we boarded it and painted it, I don’t know what we were thinking. 1 Link to comment Share on other sites More sharing options...
Conor Posted February 5 Share Posted February 5 If going to be left exposed, you'll need to paint with intumescent paint, to meet fire regs. And as Russell says, most important thing is to make sure it's been designed so it sits fully behind the insulation / window frames, not in them. Link to comment Share on other sites More sharing options...
Kelvin Posted February 5 Share Posted February 5 I fretted over this a bit too but soon realised the impact was negligible. Mine are behind the insulation or within the building albeit I made life hard for myself by not fitting the insulation until the house started going up around them rather than immediately after they were erected. I watch all these Grand Design houses that use masses of steel beams and I’ve not seen a single beam be insulated. As for exposing them. They can look pretty good if done well and in the right environment. For most homes I expect they are better covered up. Easier for fire regs too. Link to comment Share on other sites More sharing options...
ectoplasmosis Posted February 6 Author Share Posted February 6 Thank you everyone, your replies have put my mind at ease somewhat, and are much appreciated. We will of course be coating the steels with intumescent paint, then a top coat to complement the rest of the interior. All the steels sit inside the thermal envelope, aside from penetrating the floor to the footings. I’ve had standoff ears welded to the uprights to accommodate the IWI, plasterboard and finish thickness. Hoping it all works out! 1 Link to comment Share on other sites More sharing options...
saveasteading Posted February 6 Share Posted February 6 7 hours ago, ectoplasmosis said: We will of course be coating the steels with intumescent pain Not ' of course'. It isn't always necessary. The top coat must also be from the intumescent supplier. Link to comment Share on other sites More sharing options...
Mr Punter Posted February 6 Share Posted February 6 9 hours ago, ectoplasmosis said: We will of course be coating the steels with intumescent paint It is a real pain to apply and very messy. You need loads of coats to meet the required thickness. It goes manky if exposed to the elements / condensation. You will struggle to get a decent finish. Link to comment Share on other sites More sharing options...
saveasteading Posted February 6 Share Posted February 6 1 hour ago, Mr Punter said: very messy Unless applied thinly with many coats. Or perhaps the industrial, lumpy paint look suits. @ectoplasmosis at the risk of telling you what you know. Does your design state the spec? The thickness of paint is determined by the steel exposure and how chunky it is. Many steels go underprotected. Many are protected unnecessarily. The steel fails when it reaches about 300°C. I think you are elsewhere by then, one way or another. Link to comment Share on other sites More sharing options...
ectoplasmosis Posted February 6 Author Share Posted February 6 1 hour ago, saveasteading said: Unless applied thinly with many coats. Or perhaps the industrial, lumpy paint look suits. @ectoplasmosis at the risk of telling you what you know. Does your design state the spec? The thickness of paint is determined by the steel exposure and how chunky it is. Many steels go underprotected. Many are protected unnecessarily. The steel fails when it reaches about 300°C. I think you are elsewhere by then, one way or another. This is indeed news to me; I hadn't considered not using intumescent paint. Is the need for it a question for building control or a structural engineer? Link to comment Share on other sites More sharing options...
saveasteading Posted February 6 Share Posted February 6 13 minutes ago, ectoplasmosis said: the need for it a question for building control or a structural engineer? Is it needed at all? Bco probably but they may reasonably say that it is specialist. Likewise SE may not have studied this but probably has. I know because i studied it as designer and contractor and found how little it is understood. Spec help will come from a manufacturer. My favourite is Envirograf, then do them the credit of using their product. It is a matter of the exposed surface area and the mass of steel. Heated perimeter÷area. How chunky basically. 1 Link to comment Share on other sites More sharing options...
Russell griffiths Posted February 6 Share Posted February 6 My steel that is huge the one we where going to leave exposed didn’t need any form of protection if there is not a habitable room above it then I don’t think it needs it. but don’t quote me on that. Link to comment Share on other sites More sharing options...
ectoplasmosis Posted February 7 Author Share Posted February 7 17 hours ago, Russell griffiths said: My steel that is huge the one we where going to leave exposed didn’t need any form of protection if there is not a habitable room above it then I don’t think it needs it. but don’t quote me on that. We’ve got two floors’ worth of habitable rooms being supported by the steels (Victorian semi with loft extension), so highly likely we’re going to have to coat. Link to comment Share on other sites More sharing options...
Dan F Posted March 1 Share Posted March 1 You can use thermal breaks where steel leaves the thermal envelope. It seems that yours are inside though: https://www.armatherm.co.uk/thermal-break-materials/armatherm-frr/ Link to comment Share on other sites More sharing options...
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