Cresswelle Posted June 30, 2021 Share Posted June 30, 2021 So we’re mid build and builder suggested we put bifolds in across the back of our current and new back wall as will open it up. Must admit not sure why we didn’t think of this during planning but hey ho. we’ve submitted plans to BC advising them of the change and included SE calcs and the amended drawings but they are asking for u value calcs as we’ve gone over the 25% glass allowance. I’ve asked the SE and he says it’s the architect who basically has suggested I speak to the head of BC and explain that the level of insulation is increased as we’re having the loft done at the same time and we’ve increased the overall efficiency in the house so this should offset the glass. Does this seem right? I think the architect is being a bit lazy and generally can’t be bothered. I’ve asked him to make a very small change to the rear elevation drawings as requested by BC but he reckons he’s too busy. any suggestions how we can get this through. I’ve left a VM for a chat with the building control guy but not sure I’ll get anywhere Link to comment Share on other sites More sharing options...
nod Posted June 30, 2021 Share Posted June 30, 2021 Who ever supplying the glass will include the U values in the quote 1 Link to comment Share on other sites More sharing options...
Cresswelle Posted June 30, 2021 Author Share Posted June 30, 2021 Thanks. I did think this so asked the builder to get the details from the glazing company. Hopefully that will keep BC happy Link to comment Share on other sites More sharing options...
PeterW Posted June 30, 2021 Share Posted June 30, 2021 Bifolds in place of what ..? You may need a non material amendment to your planning if the openings have changed. Also, you’ll need the SEng to check the lintel and steel sizes for the openings as bifolds have very tight tolerances. TBH if you just want light, add a couple of full length floor to ceiling windows - 1/10th of the price and much more practical. Bifolds are very overrated … 1 1 Link to comment Share on other sites More sharing options...
Cresswelle Posted June 30, 2021 Author Share Posted June 30, 2021 I’ve already put an application in to planning for the amend and the SE has provided steels calcs Link to comment Share on other sites More sharing options...
PeterW Posted June 30, 2021 Share Posted June 30, 2021 Did you ask the SEng for no more than 3mm deflection ..? Link to comment Share on other sites More sharing options...
Cresswelle Posted June 30, 2021 Author Share Posted June 30, 2021 No but what is that? Link to comment Share on other sites More sharing options...
Cresswelle Posted June 30, 2021 Author Share Posted June 30, 2021 He’s aware the change is to accommodate bifolds Link to comment Share on other sites More sharing options...
PeterW Posted June 30, 2021 Share Posted June 30, 2021 So a steel will have a deflection value under load and most SEng will use standard values. That’s normally L/360 which means for a 3.6m beam it can be up to 10mm. That can cause issues with jamming of bifolds so you can ask for a smaller deflection to resolve this. 1 Link to comment Share on other sites More sharing options...
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