Is this RSJ safe?

[^woody^]

Checking the wall visually would be part of it, and if need be, some engineers could be bonded in to improve things but still without a pier.

This is one of those common situations where the experience of the builder and BCO, can trump the calculations of the engineer.

 

[cjard]

This is one of those common situations where the experience of the builder and BCO, can trump the calculations of the engineer.

And not a PII certificate between them!

Versus 70 quid for a beam calc and support spec from the right SE?

 

[^woody^]

This is one of those common situations where the experience of the builder and BCO, can trump the calculations of the engineer.

And not a PII certificate between them!

Versus 70 quid for a beam calc and support spec from the right SE?

No, because the experienced builder and experienced BCO have typically done lots of these, lots of these in the very same properties with the very same bricks and build quality, so they know what does and does not work

An SE sitting in an office reading from BS5950 does not have that benefit - it's all theoretical.

This is a 2m beam don't forget.

 

[kcseb]

Hi Guys

So I got some structural engineer calcs done: I sent photos and measurements, he did it remotely.

He specified a 2m RSJ (152 x 152 x 23 UC) with bearing plates of 250 x 100 x 15, and a "10 mm plate on top". Given the thin internal wall and existing lintel, he also specified a replacement steel post in the middle to give enough support: 90 x 90 x 6.3 square hollow section with 0.7 x 0.7 x 1.0 concrete base. Alas I don't really understand a few things:

1) what is this "10mm plate on top" of the RSJ/beam?

2) How does the beam 'sit'? Talking length-way (i.e. along the 2 metres), does the end of the beam line up with the end of the plates? Yet with the plates jutting out in the other dimension, since they're 250mm but beam is only 152mm?

3) on top of the steel post he's specified a "200x150x10 welded plate", but how/where does this fit in with point 2)?

Ta in advance guys!

 

[RonnyRaygun]

1) what is this "10mm plate on top" of the RSJ/beam?

A steel plate to increase the width of the top flange of the steel so that the wall above can sit on the beam without an excessive overhang - look into whether it would be cheaper to use a single 203UC 46 or a pair of 178x102s which would not require the top plate.

2) How does the beam 'sit'? Talking length-way (i.e. along the 2 metres), does the end of the beam line up with the end of the plates? Yet with the plates jutting out in the other dimension, since they're 250mm but beam is only 152mm?

The plate should be central above the beam, if that's what you mean?

3) on top of the steel post he's specified a "200x150x10 welded plate", but how does this fit in with point 2)?

Has he given you a detail drawing which shows the connection detail? The beam will bear on top of the post with bolts fixing them together - your SE should have specified bolt sizes and positions.

Ta in advance guys!

No problem.

Ask your SE to see if he can justify the existing foundations without forming a new pad footing (which will be very disruptive). There's a good chance that there is enough existing concrete that a new foundation is not required if the load can spread onto the foundations in three directions. The load hasn't actually increased - it's just more concentrated in the middle.

 

[kcseb]

Thanks Ronny. I've gone back to the SE with my questions. See below pic for how I understand things should be done currently.

I realise now I was being dense re plate on top of steel post: it's quite simple, with welded plate on top.

Ask your SE to see if he can justify the existing foundations without forming a new pad footing (which will be very disruptive).

Now this IS an issue. We have timber floor joists and floorboards. Not sure what to do here as he's asked for the concrete base? Should we just bite the bullet and do it, what would be the complications?

Best

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• kcseb
• 19 May 2015
• 1

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[RonnyRaygun]

Your drawings are probably somewhere near what your SE is proposing, although I would expect the 152 UC to be central under the wall with the plate overhanging both sides - might not be what your SE is thinking though.

If you can expose the existing foundations and prove that there is enough concrete below the baseplate of the post that the load can sufficiently spread to reduce the load on the soil to below approx 100kN/m2 then you won't need a new footing for the post. Of course, with it being a Victorian house there is a good chance you have no concrete foundation, just corbelled brickwork. It still wouldn't be unreasonable to spread the load through the brickwork to the ground, but you might not have the depth to spread the load.

I would say you've got no more than 45kN on the foundation, which shouldn't be too much, but you need to let your SE know what foundations you have by exposing them and then get them to do the calc.

 

[kcseb]

Thanks mate. My SE is being a bit of an arse and refusing to answer these questions saying his calcs are enough for an experienced builder to follow.

My builder is pretty trust worthy but he's not that experienced! Hence why I'm being so careful. Gonna ask the SE to come down on Saturday, will have to pay £100 but probably worth it to be safe!

Ta

 

[RonnyRaygun]

Thanks mate. My SE is being a bit of an a**e and refusing to answer these questions saying his calcs are enough for an experienced builder to follow.

I'm sure they are, but your SE might be able to give you a more economical solution re. the foundations with a bit of investigation.

I don't know what you paid, but your SE obviously doesn't want to spend any more time on the job...common stance from some consultants...