Ridge Beam

[oldmantom]

My builder has completed my loft using a wooden ridge beam. Building control are refusing to sign off the work as apparently the calculations for the beam are incorrect.

If remediation work is required to replace or reinforce the beam, I assume that is a significant piece of work. Do you have any advice on what can be done here?

 

[DevilDamo]

So an engineer has messed up the calculations or the builder hasn’t installed what the calculations have called up for?

Ridge beams can be timbers bolted together, flitch beams or a steel beam. So you may have the choice to upgrade what’s there or are having to go down the route of replacing it.

 

[oldmantom]

Thanks for the response. I think the engineer messed up.

The current beam is two thick planks (I think 220x47) screwed together. It goes into the party wall at one end and is supported by a post next to the chimney breast at the other.

If I do need to reinforce the beam, how disruptive is that. The room is finished, so to do any more work at the very least we’d need to go through the ceiling.

 

[mikeey84]

If the engineer has messed up, then whatever happens, send him the bill.

He has liability insurance for a reason!

Surprised BCO didn't catch it earlier, did you go for full plans submission?

 

[^woody^]

The current beam is two thick planks

No, that's the builder or engineer or both.

If the engineer really did under specify, why wasn't this picked up in the plans? But it's his fault regardless.

But the builder is obligated to get the roof structure inspected and signed off before he covers it up. And you need to check that the builder has not used a different beam to what was approved in the plans.

 

[oldmantom]

The engineer/builder has done an identical conversion in an identical house down the street, so we thought the building control was a forgone conclusion.

When Building Control visited they requested the post to be added (it was originally just in the chimney stack) and therefore we needed updated plans.

We were then hit by the engineer being furloughed, and then suffering badly from COVID, is it’s taken ages to get the updated calculations. But they don’t appear to reflect what was built.

 

[oldmantom]

Building Control have seen what was built.

 

[DevilDamo]

If the builder has followed the engineers’ details, then fine. If they’ve deviated, then that’s an issue. If the engineer has messed up, that is down to them to rectify. Whatever remedial or replacement work is required to be carried out will be down to the builder to sort. But don’t be surprised if this incurred additional costs of which you decide what to do about it, i.e. put it onto the engineer. Without the proper support in place, you won’t achieve BR sign off. I’m afraid it’s that simple.

 

[^woody^]

Building Control have seen what was built.

Then why did the work proceed? If the beam was not suitable, then work should not have proceeded until it was sorted out. Thats the whole point of stage inspections.

 

[oldmantom]

They saw the work, but requested the change (the post) and updated calculations. It took months for those updated calculations to arrive. In the meantime the builder made the change and proceeded with the build. It would have been expensive to pause the build, and we honestly thought it was just red tape.

I have requested, once again, for the engineer to produce calculations reflecting what was actually built. I’ve also reached out to another (more expensive) engineer to get a second view.

 

[DevilDamo]

It would have been expensive to pause the build

More expensive than potentially having to replace the beam in its finished/practically complete state?

 

[tony1851]

@op; what's the span of the beam?
And what span of flat roof/pitched roof is it supporting?
Two 9" x 2"s screwed together make a pretty hefty beam; as it is only supporting a roof, the SE is allowed to assume a higher stress in the timber.
Do the calcs show the bending stress and deflection in the timber, and the grade (C16 or C24)?

 

[oldmantom]

The span is 5.4m I think. The calculations don’t show the right measurements. I think the next step is to get another engineer in to try and do the calculations correctly.