Supporting RSJ/foundation advice please

[Hobo84]

OK so...

I've been planning a wraparound extension to my semi-detached house.

I'll be removing the rear wall of the house to open up the extension which will require steel. My problem lies with how to support this steel. The proposed solution is when knocking down the rear wall, to turn them into columns (which may need padstones/reinforcing) and to place the steel on these. The engineer employed has looked into the foundations that these columns will sit on and advised they aren't adequate and need strengthening. His remedy is to arco prop the rear wall, remove the existing foundation and install a reinforced concrete beam. However all builders (7 to date) I’ve asked to quote have either; not been interested as the job isn’t worth their time or said it’s over engineered and unnecessary (again not interested). I’ve gone back to my engineer and asked about another solution and he’s been inflexible and querying who these builder are, whether they’re any good. Building control advised me that they will only follow what the engineers have instructed and I need their plans to change before I start work.

So I’m currently stuck in limbo with where I stand. Is the engineer entitled to offer another solution? What other reasonable solutions are there (mass poor underpinning, steel goal posts?) Is the RC beam sound/Shall I keep ringing builders? Should I get another engineer?

It’s been over 2 year since I started planning this extension and I’m starting to reach boiling point and about to jack it in

The beam will be roughly 5.5 meters in length. I'm trying to upload the plans.

Thanks,
Neil

 

[^woody^]

I've never had to alter foundations when putting in steels of this type in similar situations.

Why can't you just submit the details for the beam and padstones and nothing else?

 

[tony1851]

Is the SE specifying newly-built brick piers on their own foundations, to support the ends of the beam?

It's not often that the existing brickwork is not able to support a beam, because the bonding-effect of brickwork helps to distribute the load over a larger area of the foundation.

Maybe see another SE - your current one won't change his mind because otherwise he'd look a fool. Some SEs purposely over-spec things just to cover themselves, and unfortunately the client ends up paying over the odds for the privilage.

 

[Hobo84]

I've never had to alter foundations when putting in steels of this type in similar situations.

Why can't you just submit the details for the beam and padstones and nothing else?

I've been told the existing foundations will not support the newly distributed weigh once the steel is in place (the load at either end). The dimensions are 640mm deep and 150mm thick. It's hard to determine the width (not sure if the existing property is strip or raft), but the toe projects out 150mm from the external masonry leaf.

 

[Hobo84]

Is the SE specifying newly-built brick piers on their own foundations, to support the ends of the beam?

It's not often that the existing brickwork is not able to support a beam, because the bonding-effect of brickwork helps to distribute the load over a larger area of the foundation.


Maybe see another SE - your current one won't change his mind because otherwise he'd look a fool. Some SEs purposely over-spec things just to cover themselves, and unfortunately the client ends up paying over the odds for the privilage.

He's not asking for new piers. That may have been misleading, sorry. Just padstones for the steel to sit on and 'touch ups' if any brick is damaged taking down the wall.

I was aware this was the case and really hoped building control would offer some advice

 

[^woody^]

From past experience all the existing foundations (some very similar to yours) have coped with the different loading from a steel.

I've done many of these opening up the back extensions, whole width and corners, and this has never been an issue. It seem that if the existing foundations are adequate for the existing wall, then they will do for the new steel.

Sometimes we've needed to rebuild walls though - under the bearing, or rebuild in a different stronger brick or block. Never needed to touch foundations though, unless widening for a new pier.

 

[Hobo84]

From past experience all the existing foundations (some very similar to yours) have coped with the different loading from a steel.

I've done many of these opening up the back extensions, whole width and corners, and this has never been an issue. It seem that if the existing foundations are adequate for the existing wall, then they will do for the new steel.

Sometimes we've needed to rebuild walls though - under the bearing, or rebuild in a different stronger brick or block. Never needed to touch foundations though, unless widening for a new pier.

That's the opinion from the builders I've had onsite however building control will only sign it off if the engineer agrees and amends his plans. From our last conversation I'm guessing he will not be willing (which I can totally understand, it is his profession after all). Is it likely another engineer will come to the same conclusion (I assume all SE work to simular guidelines) or can they vary?

 

[tony1851]

(I assume all SE work to simular guidelines) or can they vary?

There are no 'guidelines' - it's down to experience and common sense really.

Your SE will be assuming that the load from the beam-end will be going vertically downwards, when in practice it will spread outwards into the wall due to the way the bricks are bonded.

Ultimately, by the time the load reaches foundation level, it will be spread over a wide area, and the ground beneath the foundation will hardly know the difference.

As per Woody above, you hardly ever need to have new founds in cases like this, though you do need to tidy up the brickwork at the ends, and install padstones.

You either do the foundation as per your stupid SE, or start again with another SE.

 

[Hobo84]

(I assume all SE work to simular guidelines) or can they vary?

There are no 'guidelines' - it's down to experience and common sense really.

Your SE will be assuming that the load from the beam-end will be going vertically downwards, when in practice it will spread outwards into the wall due to the way the bricks are bonded.

Ultimately, by the time the load reaches foundation level, it will be spread over a wide area, and the ground beneath the foundation will hardly know the difference.

As per Woody above, you hardly ever need to have new founds in cases like this, though you do need to tidy up the brickwork at the ends, and install padstones.

You either do the foundation as per your stupid SE, or start again with another SE.

OK - Thanks for the advice. I'll contact another SE.w