Project Management Dormer Double Extension

[Seasailor]

Hi All,

 During the Covid lockdown I was looking for something to do. I decided to project manage a double extension on my dormer bungalow. Planning and Building control are all sorted and currently I am clearing out all the first floor ready for the start in a few weeks. Steelwork was a bit of a shock - Two 11 m purling beams and a  11m UB at first floor level for the long extension. There are shorter steel beams at the other side (8.8 UC) for the short extension. These three beams will require a contract lift onto their designated padstones. What is puzzling me is why the structural engineer has insisted on doubling up the existing (FF) joists with 75mm x 150mm joists at 400mm centres and for the first floor area which spans the downstairs living room he has additionally specified 150 mm x 150mm wooden beams alongside the existing beams at 400mm centres (Nightmare for installing new services due to limited space.) The new dormer structure is totally supported on the steel beams via load bearing walls. The upstairs before the conversion had two first floor bedrooms from the original build and the original upstairs beams are the same size and spacing as the downstairs floor beams. I would appreciate someone pointing out if there is something that I am missing

 

 

 

Edited April 19, 2021 by Seasailor
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