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I recently asked my structural engineer to provide some calculations and drawings to remove the arch and further open up the opening between the double fronted sitting room of my 2.5 storey (2 at the front and 3 at the back) semi-detached Victorian house.

I am only opening up the left wall 60cm and squaring off the top of the opening (removing the arch) so feel his suggestion is drastic.

Here is the drawing he has provided:

engineer's drawing

Click for full size image

which includes the following things I was hoping to avoid:

  • Building a brick pier when a wall already exists
  • Digging up the floor and laying a concrete footing on the left
  • Inserting a concrete lintel on the right.

What do you think? Is this over the top? I want to use him for other work but this has put me off.

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What did your engineer say when you asked why all that additional structure is needed? –  longneck Dec 30 '13 at 15:19
5  
So... Instead of trusting a structural engineer, you want advice from a bunch of yahoos on the internet? –  Tester101 Dec 30 '13 at 17:42
    
Do you have structural drawings of what is below and above>? –  wallyk Dec 30 '13 at 19:58
    
@Tester101 If its on the internet, it must be true... the Engineer ain't on the internet so we have to verify Him/Her with the internet somehow. How else do you suggest we verify the Engineer? –  WernerCD Dec 30 '13 at 20:15
    
@Tester101 I never trust a professional's advice about something important without verifying it independently. Yahoos on the Internet do not have the same interests as the engineer. It's smart to ask them. –  Edwin Dec 31 '13 at 1:59
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2 Answers 2

There isn't enough information in that sketch to verify calculations (for instance, we have no idea what's on the floor above), but here are some reactions:

  • Removing 60cm of support may be significant, depending on how much load that wall was carrying.
  • If the arch is structural, removing it requires additional support.
  • Your existing building may not be structurally adequate. If you're making changes to those supports, you are probably obligated to bring that portion of the structure up-to-code.
  • The structure is of no use if there's not an adequate foundation to support it. Your drawing doesn't show any information about the existing foundation, but shrinking the supports from walls to piers may concentrate the load beyond what the existing footings (if any) can support.

I agree with @longneck, you should talk to your engineer about your concerns. There may be ways to avoid some/all of these tradeoffs, or maybe you decide that it's not worth the effort.

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It's hard to say without knowing exactly what is there at present.

While it is not unknown for structural engineers to over-specify something, they will be sure that they don't under-specify. It is certainly possible that a different engineer could propose a different solution.

I'm assuming from the details that you are in the UK. You will need Building Regulations approval for structural work like this, and they will ask to see structural calculations, so there's not likely to be much scope for cutting an engineer out completely.

I'm guessing that the engineer has concerns about the capability of the existing wall in terms of load bearing or stability in terms of the requirements for supporting the amended structure.

As the wall you are modifying is an internal wall, it is entirely possible that it will have minimal (or even no) foundation under it (this is not unusual for older properties), which could cause the existing wall to drop when the "new" loading of the beam is applied to the modified wall - hence the need for the new foundation.

It is possible that the existing wall construction is inadequate for the loading that will be imposed once the beam is in place. Also, bear in mind that the accepted "standards" for construction vary with time; what may have been accepted as the norm when the house was built (which vastly pre-dates the Building Regulations) might not be acceptable now.

The lintel on the right hand end is certainly needed; the usual minimum accepted bearing for a beam is 150mm. It's likely that the wall you are bearing onto is only 100mm thick. The lintel will spread the (almost) point load of the beam's bearing by an acceptable amount, so that the compressive strength of the existing wall is not exceeded. Actually, I'm a little surprised to see that a concrete pad stone hasn't been specified for the left hand end of the beam, especially as it appears that the beam will not bear centrally on the new pier.

In summary - while there is a chance that there may (or may not) be a little over-specification (you haven't supplied sufficient information for a qualified reply and I'm not qualified to assess your engineer's calculations anyway). I'd hazard a guess, based on my experience, that it certainly is not excessive.

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