Taking out an external wall

[NGEddie]

I'm getting a builder in ti take out an external wall between by kitchen and conservatory. The builder has suggested an engineer to do the load calculations to be sure building regs are met.

What I need advice on is whether the engineer is giving us the best solution or the easiest for him to draw up.


I like to limit size of Piers protruding into the room to support the new lintel so the engineer has given 2 options:
- Steel box frame - expensive
- Piers built of engineered bricks

Engineered bricks seemed like the best for cost reasons and I asked him to see how small he could make the Pier. What he's drawn though are Piers projecting 440mm into the room, which is double what I was hoping for.
Questions:
1) The drawing shows the Pier made up of 1 skin of my current external bricks and 1 skin of 70N/mm² engineered bricks. Would it not be possible to buid the Pier of 2 lines of engineered bricks to make it stronger smaller?
The engineer's response here is only that it wouldn't make much difference.
2) The calculations show the Pier is currently spec'd to support 74kN and the factored load on it is 54kN. Would that not allow for the Pier to be ~30% smaller and still support the load?
The engineer's response here is that he has to think about latteral loads and eccentricity.
3) In the most recent communication the engineer has stated that building Regs Part A actually requires a 550mm Pier. I couldn't find that in the Part A doc, anyone heard of that?


Obviously I understand that concern 1 is that my house stands up, but for me concern 2 is that this Pier will be staring at me for the next 20 years and I just want to know that we have done what we can to minimise the projection.

Thanks,
Eddie

 

[tony1851]

Your engineer is correct in that the pier has to support not just the vertical load, but also be capable of resisting the lateral wind load on the building.

The recommended minimum pier dimension is shown on p27 of the Approved Document A. The alternative would be to go with a steel frame.

By the way; you are taking out an extrnal wall to a conservatory. Suggest checking with building control.

 

[^woody^]

If the engineer has deemed wide masonry piers are needed, and you don't want them, then you ask him to design something which wont need wide masonry piers - steel columns, or extend the beam if possible

There are lots of properties with no return piers and wide openings, and no extra columns or anything, and I often wonder why these have not just fallen down years ago. It must be something to do with today's structural engineers

 

[RonnyRaygun]

If the engineer has deemed wide masonry piers are needed, and you don't want them, then you ask him to design something which wont need wide masonry piers - steel columns, or extend the beam if possible.

Yup, get the cheque book out

There are lots of properties with no return piers and wide openings, and no extra columns or anything, and I often wonder why these have not just fallen down years ago. It must be something to do with today's structural engineers

Yes, a certain amount of arse covering going on...if a wall is removed the stucture is obviously less stable than before, and if a slight breeze brings everything tumbling down, the SE is going to be in a whole heap of trouble...hence the usual solution of designing a box frame to resist the wind loads, or alternatively brick piers.
The walls in new buildings tend to be well restrained with robust strapping details so the walls can withstand the wind loads without any further restraint. Walls in older buildings are usually nowhere near as well restrained.

 

[^woody^]

It seems to me that post and beam frames have only become "popular" in the last 20 years or so.

 

[RonnyRaygun]

Have there been any major changes to Part A in the last 20 years that may have made lateral stability a more important design consideration?

I do know that brick piers often have to be very large if you actually try to design them to resist notional wind loadings...but then I've also seen them regularly "eyed in"...

 

[NGEddie]

OK, it sounds like if the engineer says it is needed for latteral load reasons then I'm in no position to question it. Thanks all for your input!

 

[freddiemercurystwin]

You say you are doing this to Building Regs (and rightly so) so be aware that Building Control are likely to raise an eybrow (or 2) to you (presumably) removing your existing door between your house and conservatory ...

 

[NGEddie]

Why's that Freddy?

My builder's advice has been that I wont need planning, just structural calculations and a SAP count.

Is there anything I need to be worried about?

 

[freddiemercurystwin]

SAP's are the fellas!