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Extending an extension (rsj question)

We have an existing extension of about 2x4m we want to add to this by 3m to make a 2x7m extension. We also want to remove the load bearing wall in between. The existing extension has an RSJ fitted. We think the joists run lengthways (parallel to existing RSJ).

Our SE suggested replacing the existing RSJ with a new 7.6m RSJ. However we understand that to do that would mean disturbing the upstairs rooms (inc 2x tiled bathrooms) when supporting the swap. Would it be possible to do it without interfering with the first floor?

Alternatively, could we extend the existing RSJ and would we have to have a supporting pillar?

Or could we just put a part or full beam below the existing beam (accepting we'll then have a down stand)? But how deep would the down stand be?

What would be the cost difference in the different options?

1 Answer from a MyBuilder Extension Builder

Best Answer

If it requires joists to be flush then it will require needles to be inserted snd yes, will encroach above floors of upper rooms. It may be possible to support existing beam and install new below. Strongboys and accrow props will have to be used. The cost difference is disturbance to above as dry packing with sharp sand and cement is required. You will also need calculationd showing the old steel and extra weight is calculated for. Support piers may need underpinning with 1m3 cubes of concrete and again dry packing. Hope this helps.


Answered 19th Oct 2016

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