Structural Engineer vs Fabricator: FIGHT!

Hi all - I'm currently having a kitchen extension built, and due to the pandemic and a variety of other issues it's fallen to me to kind of manage the thing. A long story short: I'm knocking through two walls and was recommended a structural engineer by my building inspector. They came to site, measured up and have sent me and the builder a long doc which includes a diagram of the beams and how they are to connect and a bunch of pages with loads of complex calculations. The builder has taken this to a fabricator as essentially the beams need to be connected, so the right holes and a bracket need to be made, but he's complained the structural drawings have no actual measurements on them. The engineer has come back and said it's not his job to do measurements and in 1500+ jobs he's never had to do that, and I have a stalemate. Of course I'm in the middle copping it from both sides when I have no idea who's at fault. To me it does seem odd not to have measurements, but the engineer states that's the job of the fabricator and his job is to worry about loads. When I asked if the measurements affect loads he said yes but not enough to worry about. Can anyone help me shed some light on this? Thanks!

It isn't the SE's job to provide accurate measurements of lengths of beams, or positioning of holes for bolted connections etc. The SE just does the analysis and provides the optimum section size of beams; a few cm out in lengths makes no difference to the size of section chosen.

The builder should provide the fabricator with actual lengths required, allowing for the lengths of the bearings. For the bolted connections, some fabricators will come to site with equipment to drill the holes in the correct position.

tony1851 said:

or positioning of holes for bolted connections etc.

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He should do this as holes and connections are part of the design.

Thanks for that. I don't know much about the fabricator, the builder says he uses him. I've paid the fabricator £745 for 2 beams over a 3.2m opening and 3 over a 1.8m opening, plus the fabricating itself. He hasn't offered to come to site - does that seem fishy?

Apart from the section sizes the SE wont provide measurements for manufacture/fabrication unless its specialist design - which this is not.

Normally, someone (the builder) measures and takes those measurements to the steel supplier, or if things are to be made on site (as opposed to just supplying a steel beam), the fabricator will either come and measure or just bring the stuff and make it up on site.

^woody^ said:

Apart from the section sizes the SE wont provide measurements for manufacture/fabrication unless its specialist design - which this is not.

Normally, someone (the builder) measures and takes those measurements to the steel supplier, or if things are to be made on site (as opposed to just supplying a steel beam), the fabricator will either come and measure or just bring the stuff and make it up on site.

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Thanks Woody that's helpful. If this isn't too 'specialist' was even getting a fabricator and the quote above over the top or could it just be done with a drill and steels straight from a merchants? Just trying to work out if I'm down the garden path here

We would rarely use a "fabricator" (although it may be semantics) as such, but just go to the steel supplier and tell them what we want, give them sizes etc and if we want holes or welding just tell them what we want too. The supplier is generally so experienced that they know what to do anyway or will tell us that "this or that" would be better.

To us, a "fabricator" is someone different to the supplier who works on the steel to make more complex forms, as opposed to just drilling holes or welding a plate here and there.

So in context, I wonder if this "fabricator" that the builder has engaged is what is really the "supplier" (who can work with the steel), or is it an additional person who is going to work on the steel for you and so expects the correct sizes etc?

^woody^ said:

We would rarely use a "fabricator" (although it may be semantics) as such, but just go to the steel supplier and tell them what we want, give them sizes etc and if we want holes or welding just tell them what we want too. The supplier is generally so experienced that they know what to do anyway or will tell us that "this or that" would be better.

To us, a "fabricator" is someone different to the supplier who works on the steel to make more complex forms, as opposed to just drilling holes or welding a plate here and there.

So in context, I wonder if this "fabricator" that the builder has engaged is what is really the "supplier" (who can work with the steel), or is it an additional person who is going to work on the steel for you and so expects the correct sizes etc?

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thanks, you might be right. Does the price I mentioned suggest perhaps that’s the case?

I'm not up to date on steel prices, but it depends on the section sizes, and what you are having drilled or welded. So perhaps someone else has an idea of costs.

If its a few holes along the beams to bolt them together then that's not a big cost. If you are joining them end-to-end, then that's a plate and holes and more time.

Also, are these beams coming with undercoat or bare? Are the bolts and spacer tubes being provided.

Can't you check up on the fabricator's factory address?

Is one beam coming off the other at a right angle? I’d say the builder should only need a tape measure and a square to be able to tell the fabricator what to do.

^woody^ said:

He should do this as holes and connections are part of the design.

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For 'simple' connections (eg those that do not transmit bending moments) the SE does not normally design the connection him/herself but leaves it to the fabricator. (In the OPs case where one beam is joining into another at right-angles (?) this will be a simple connection).

This is because there are many ways of achieving simple connections, eg it might be made with either two 20mm bolts, or just as strongly with four 12mm bolts. It would be unduly restrictive if the SE were to demand only 20mm bolts, while the fabricator might only have 12mm bolts available, but which would be just as good.

In the case of moment connections (eg beam splices and goal-post frames), the joints are critical and the SE must specify bolt grades, diameters and spacings and give detailed drawings, as this is specialist work which the fabricator will not be able to design.