Stub Walls for beam

[Crakkers]

Just come back to my posting as I thought it had died - I can see it's still very much alive!

Just wondering what size of nib wall would be expected / minimum ?

Also, I am told you can hide a beam in the ceiling? Does this give a flush ceiling to the knock through? And how on earth do you achieve this? Surely the upper floor joists sit on the wall being removed, so if the rsj goes into the ceiling what happens to the joists? Just can't visualise this!

Thanks so far guys!

 

[tony1851]

There are two issues here: 1. designing the beam to support the loads above and 2. ensuring that the lateral stability of the house is not compromised.

1. is relatively straightforward for the SE to specify, and there are a number of beam-sections which will do for domestic loadings. Ultimately it will be down to the most cost-effective section for the particular span.

2. is more problematic. If you are removing the majority of the rear wall at ground floor level, then your SE might design a goal-post frame. The joints of this will be designed to be stiff enough to provide the necessary rigidity.
The alternative to a frame (which is expensive) is to do calculations to prove that the house as a whole is stiff enough without recourse to a frame. As you are a 1930s semi, you may have sufficient walls remaining at ground floor level to achieve the necessary stiffness. Problem is, it's a lot easier for an SE just to tap numbers into a spreadsheet to design a frame, than it is for him to sit down and do the number crunching by hand (there are no spreadsheets for this process) to prove that you don't need a frame.

(As for leaving a nib, it may or may not be necessary - it depends on the loading, and the condition of the supporting walls).

You can hide a beam within the depth of the floor above, but if the floor joists are spanning onto the beam, it involves more work in cutting the joists and fixing joist hangers, so is more expensive.

 

[Crakkers]

Thank you, most informative.

Joists upstairs run parallel to the wall being knocked through.

Not too bothered about a flush ceiling, but want the nibs as small as poss.