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Is a rsj needed

I am having a 14m x 4m single storey extension added to the back of my house. It will be split into three parts, two sets of 3m bifold and one 5m bifold with two .5m column dividing them. The differences will be added to the extreme edges.

The architect says that we will need an rsj over each opening, and one from each column to the house, making a total of 5 rsj's Is this correct? I believe that bifold are loaded from the base and not hung from the top and it is a single storey. There will be a 2m x3m Sky light centralised in the roof, but not sure if this makes any difference. I have read that a single timber could be used instead and is a lot cheaper. It just seems a lot of steel work.

Any feed back would be appreciated. Thank you Nancy

2 Answers from MyBuilder Extension Builders

Best Answer

Hi Nancy,

I would say it would be prudent, and possibly best, to engage a competent Structural Engineer to 'prove', by calculations, what will work. Whatever materials you use, you must demonstrate, by 'calculation', that it is suitable and sufficient to bear the weight of the imposed loads over. Also, I'd ask the Strutural Engineer to 'prove' the columns are of suitable integrity.

You could look up the 'Catnic' Lintels range, and other makes, to see what design performance they offer, as a possible guide. These are lightweight, and can come insulated. I used 'Catnic Cougars' on my build, and they met the requirements of Building Control.

Building Control will want it demonstrated that the materials used are capable of achieving the necessary performance.

Hope that helps, many thanks, Jason, CBuildE.


Answered 20th Oct 2015

Hi Nancy
I agree with Jason that hiring a structural engineer would be a necessary step to take for giving you the best options and in any event building control will want to see calculations for any load bearing supports/beams.
With regard to the bifold doors, they are more commonly installed and operate much better when hanging from a perfectly smooth and level steel beam as oppose to rolling on a not so accurate floor. The beam will more than take the weight of the doors and you can guarantee that the doors will work perfectly when installed in this way. Only the guides are installed into the floor. It might be that the Architect has presumed this will be the case. A timber beam of the same size would move (expand/contract) over time with the changing weather conditions and then you would have issues with the doors.
I hope this helps
Best regards
Brendan - Moloney Contractors


Answered 3rd Nov 2015

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