Rsj beam or goal post beam required.

[Bouba]

Planning on rear extension on a end terrace house.Will be going through building regs and a proper insured structural engineer.Just looking for general advice with regards to requirements,so I could get a rough idea of costings.

Please see attached pictures.(they are current house elevation and what is proposed)What would be required if i need to remove the external rear wall and side wall of the house in just the kitchen area.Am I looking at RSJ or a goal post beam which obviously be more expensive.

How does a structural engineer decide if the loading on the wall is sufficient for RSJ without checking the foundations.Is it by default or hit and trial basis.After all he does all the calculations,which is then passed by building control and then the builder takes over.But who is responsible for checking foundations loads.
Finally what is the maximum load a solid 9" wall can take.In my case if he majority of rear wall is taken off and the RSJ is on 2 colums on each end,will it be sufficient.



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[Bouba]

The pictures are present elevations and proposed.Please advice if anyone has done a similar extension and costing for the beams.I am based in Essex.
Thank you.

 

[tony1851]

With regard to the foundation; the SE obviously doesn't know the bearing capacity of the soil, so he will choose an 'average', reasonable figure for bearing capacity.
He will state in his figures that it has been assumed to cover himself.
But ultimately, it will be your responsibility to satisfy yourself that his assumed figure is adequate.
To be absolutely sure, you would need to get a soil test done = £££,
but most people don't bother, and 99 times out of 100, everything's OK.
Just hope that you are not the 100th!

 

[Bouba]

thanks Tony.Any ideas if looking at Rsj or Goal post beam. The L bit will be coming out from corner of house as shown in Pics.

 

[Bouba]

I have now spoken to couple of SE's and they are advising RSJ's to be seated on 2 pillars on either ends with 200mm bearings.One has said that on the top of head it is most likely going to be 2x (6x4) welded together for the rear wall to be removed.My only concern is what happens to the flank side of the wall.Does this bolt into the other one

Also is it possible that solid wall construction is adopted, and then later internal insulation is used to bring up U values.I have not spoken to building control yet,so do not know if they will allow it.Always hear the old tradesmen saying that solid walls are more stronger than the cavity wall construction these days.I

 

[jeds]

The loads aren't going to be that great looking at those openings. And the beams they've suggested are pretty small. As Tony says, 99 out of a hundred the foundation will be plenty for those loads. The foundation, supporting masonry and mortar joints should be checked when exposed. These will be checked by building control anyway but you could always call the engineer in to have a look. If it turns out something isn't good enough you will have to have an alternative support designed. Which might be rebuilding the piers in 7N block. Possibly a pad foundation. Or maybe a column.

 

[Bouba]

thanks john. when you say loads is not going to be great,can you please elaborate. The whole corner of the house will be supported by beams. The rear wall is around 5 metre wide and side wall about 3 metre. i wish to convert loft in future. thanks.