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Kerry Rhodes

Can I avoid a cold bridge with balcony steel?

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We have a SIPs house design with a cantilevered balcony and void area that requires steel supporting posts and beams - green lines in snapshot below. To avoid cold bridging we have moved the outer steel support post inside the SIPs wall, but I'm not sure how to approach the central steel beam (labelled 10 in the pic). Is my only option to insulate and box the beam internally?

Your help would be appreciated please.

Thank you 

Screen Shot 2021-09-30 at 11.23.37.png

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There are special adapters available for this. A butt joint between the internal and external lengths of steel, bolted together in some clever, non-continuous way.

I  have prodded them at exhibitions but could not get a cost indication.

 

ahhh. found one using the interweb.  over to you.https://www.farrat.com/structural-thermal-break-connections?utm_term=thermal break pads&utm_campaign=Thermal+Breaks-Leads-Search&utm_source=adwords&utm_medium=ppc&hsa_acc=5261485987&hsa_cam=13260167897&hsa_grp=122980897859&hsa_ad=523953648699&hsa_src=g&hsa_tgt=kwd-382966641357&hsa_kw=thermal break pads&hsa_mt=b&hsa_net=adwords&hsa_ver=3&gclid=Cj0KCQjwwNWKBhDAARIsAJ8HkhcB8DpTz-Xk9vOiET718z4T9BDTbmE1D1TFVqfLh4KgC1rURMVP-EIaAqGlEALw_wcB

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We have exactly this issue with a balcony in our house (except our beams are more like 3 and 9 in your drawing).

 

Thermal breaks as mentioned by @saveasteading are one option.

 

You mention insulating the beam inside. You can also insulate the outer end of the beam as well. Anything that slows heat entering (within the house) or leaving (in the balcony) the beam will help. 

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I can see no reason for this beam to be continuous as the loads inside will be far higher than the balcony so it would be better to thermally break the beam inside and construct the cantilever separately (but connected).

in the past we have done beams with plastic flange and web plates to make a continuous beam but electrically isolated.

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We've used armatherm structural thermal breaks in a variety of places, which like the Farrat are I think commonly used for steel balcony connections

https://www.armatherm.co.uk/products/frr-structural-thermal-break-material/

 

They can provide bushings and washers as well

 

thermal bridging

 

Not expensive.

 

I believe stainless steel bolts give reduced heat transfer.

 

While I'm not a professional, even if I wasn't concerned about heat transfer I wouldn't want any structural steel running through the envelope on a building intended to last 100+ years. What if the outer end gets wet and rusts? Wouldn't want to have to replace the entire beam. In that, I'd want the balcony to be replaceable independently of the main structure.

 

We don't have any balconies, but we have an awning bracket which is similar. The stuff that looks like wood is the armatherm FRR:

 

image.png.e49af3d89a40719e35991154b75565f8.png

 

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Thanks all, some really helpful advice and good tips. I'll liaise with SIPs@Clays and request the thermal break at a join in 10 as it leaves the house for the balcony. thanks again...will update the post once I have an outcome.

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46 minutes ago, Kerry Rhodes said:

I'll liaise with SIPs@Clays

 

TBH it's a red flag that this design was proposed as-is at all? Suggests the designer either isn't worried about massive cold bridges, or just didn't spot it?

Had you specified that these kinds of things should be avoided? Where else might there be issues? For example what is the detail at the 'north' end of beam 4?

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18 hours ago, kxi said:

 

TBH it's a red flag that this design was proposed as-is at all? Suggests the designer either isn't worried about massive cold bridges, or just didn't spot it?

Had you specified that these kinds of things should be avoided? Where else might there be issues? For example what is the detail at the 'north' end of beam 4?

Yes I was surprised that it hadn't been picked up earlier given that we've had great service from them to date. I hadn't specified as such but I have had general chats about why we chose SIPs and KORE foundation system together, to get an airtight warm home. Re the north end of beam 4 - supporting post is moving inside the wall of the house and beam above is being reduced in length to bring it inside too.  Have gone through the rest of the design with them yesterday and we haven't identified any others. They are now looking into splitting the balcony beam. Its great to have this forum to guide me thanks...getting involved in detail very new to me but I'm enjoying it!

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