Restoration & Refurbishment Question

Is rsj too big?

I've recently had a structural engineer draw up some plans for a rsj I want fitted. We're having a structural wall taken down between the kitchen and lounge. The wall is 3.4m and used to be the external wall to the house until a double storey extension was put on the side. The wall in question is a cavity wall made from standard construction.

After receiving the plans my builder has informed me that the rsj's suggested are far too large for the opening and will require more equipment and labour to fit, thus costing me more money. The drawings suggest using 2 254x146x37ub? Bolted together with steel plates welded top and bottom with the addition of 2 pillars built from engineered brick. But my builder whom has years of experience believes we'd require 2 rsj sizes of 203 without the addition of the engineered brick, and no welding of plates.

The engineer will not adjust his plans as he says everything he has calculated is correct by British structural standards. I'm a keen diyer and have renovated 1 flat and 1 house, but this job calls for experts, can anyone help? I can post drawings if required.



After reading the responses from the professionals I'm going to approach another Structural Engineer for a second opinion, I know I'll have to pay for this service but feel it's the best option.

Thanks for all your responses it's very much appreciated.

I how now received new calculations from a structural engineer that has been in the game for 20 odd years. The beams are much smaller than the original calculations and have been resubmitted to the council. Fingers crossed work will start next week.

Thanks for all your posts.

6 Answers

Best Answer

I come across this a lot. Builders always think they know best, if he is the 'expert' then let him provide the calculations.

The engineer should have taken into account many other factors such as point loads, wind loads, live loads, floor loading, stability, etc.

From the sizes you have stated I think they sound about right although a bit heavy but then I am unaware of all the factors; of course there many ways to support an opening, as my engineer would have used a PFC (channel section) with top and btm plates, but then depth would be greater some where between 300-400mm to give a flush ceiling.

So how did your builder price the job without knowing the size of steels? What extra equipment is he referring to? And labour, what did he allow and how many more people does he need? I would suggest this is a two man job no matter what the size of beam with the use of a Genie lift.

If you're still unconvinced then you will need to approach another engineer for a second opinion as they are the ONLY ones qualified to do so, but that will cost.

Have you spoken to your Building Control Inspector? Worth a chat!

Answered 7th Oct 2013

JLM Architecture Limited

Member since 5 Sep 2013

Ask your builder does he carry the necessary PI insurance to back up his claim in case the house falls in, then see how quick he passes this back to the structural engineer !

Answered 7th Oct 2013

E.d construction (nw) limited

Member since 3 Oct 2013

Hi, just speak to Building control and go by what they say.

(Greengate Builders)

Answered 7th Oct 2013

Greengate Builders

Member since 10 Apr 2009

You need experts? The builder is your expert!! Anyway the engineer rules on this.

Answered 6th Oct 2013

Roc builders

Member since 25 Aug 2011


The world is full of disasters where "experience" has taken precedence over the "right way". The wall is still a supporting wall if the original roof trusses have not been reconfigured when the extension was built.

The answer is simple, ask the builder for his calculations for the structural support that he is proposing.

If he can't, go with the person who can.

Answered 7th Oct 2013


Member since 4 Oct 2013

So it appears that the builder priced the job to be done his way and upon receipt of the engineers specification, has got it wrong.
As the job in hand is structural and therefore requires building control, you should always get engineers calculations first in order for a builder to provide costs.
We get asked to price all sorts of structural refurbishments and extensions where the customer has not sought planning or building regs and it cannot be done with any accuracy.
Yes the new method for your steel beams is more expensive and the engineers method is always right as he is the one who has the indemnity insurance to cover a mistake. I have found that younger engineers have a tendency to over spec certain building projects so your only option is a second opinion from another professional and by that I mean a chartered engineer or carry on with the specification that you have.

Answered 10th Oct 2013

D B Enterprises

Member since 17 Jan 2013

Need help with your project?

We have tradesmen ready to help you. Post a job, read reviews and hire today.

Post a job

Need some help?

Post a job on MyBuilder to find quality, local Restoration & Refurb Specialists who can help you with your project.

Search all questions