Steel bridging different thickness walls

[ninro]

Hi we're building a single storey extension. We ideally want to put a steel across 2 walls of different thickness. one is the old part of the house 25 cm thick, other is a new extension 30 cm thick. SE says this is tricky due to the different width of walls. I've sent him the idea in the picture below which I think could work. The steel which needs to be stronger than standard lintel because it would be the lintel over a doorway and also has another steel perpendicular to it sitting on top. I am wondering whether steel spreader plates would work just as good as padstones. Does this look viable? Thanks

 

[George_engineer]

Is there a wall above? That is what the steel needs to be centered on.

Idd be inclined to rebuild the end of the 9" wall with a pier to match the width of the cavity wall.

 

[ninro]

Thanks.
It's flat roof single storey room with similar extension attached. No wall above to support. The perpendicular steel above this proposed lintel/steel bridges a 4m gap, flat roof through web.
So a 30cmx30cm pier on corner should be enough?
I've since found these pictures which do have a wall above to support so our loads should be much lower.

 

[ninro]

I think I can deduce from the pictures I posted of someone else's project that these would cause thermal bridging problems.

 

[ninro]

Hi we're building a single storey extension. We ideally want to put a steel across 2 walls of different thickness. one is the old part of the house 25 cm thick, other is a new extension 30 cm thick. SE says this is tricky due to the different width of walls. I've sent him the idea in the picture below which I think could work. The steel which needs to be stronger than standard lintel because it would be the lintel over a doorway and also has another steel perpendicular to it sitting on top. I am wondering whether steel spreader plates would work just as good as padstones. Does this look viable? Thanks
View attachment 307609

Is it possible for the end of the new wall to have no cavity, so it is solid masonary? Then a steel would sit across old wall blocks and onto new wall blocks, no need for the padstones in this orientation.

 

[Mr Chibs]

Perhaps you should just have your SE work it all out... tricky or not.
I would have thought he comes across this situation weekly.

You could do with putting more information on here, sizes, photos etc.

 

[ninro]

Our structural engineer isn't really being very helpful about this, he says ask architect who's too busy. Neither is building control.
What would really help us is if we were allowed to build a new wall with a smaller cavity, 50mm, and then perhaps add 50mm insulation on inside of new extension room so that bricks and blocks match up on both sides.
anyone think this is likely to be allowed. I asked building control, they just say submit plans.

 

[George_engineer]

Yes this should be fine but you need to get the u-value checked.