This was the comment from my surveyor when I asked him to explain why he had asked a customer to engage a structural engineer to check a steel beam spanning 1.4 metres - which even by my rudimentary knowledge of structures would probably have been OK.
The episode started with an irate customer ringing to explain that we had previously agreed that the beam would be OK and that it wasn’t until this surveyor had turned up...you can probably guess the rest of the conversation, it’s not really for printing in this magazine.
It might surprise you to know that actually this statement was true, we had agreed that it would be OK. The customer had originally contacted our office to see if they needed building regulations for making an opening in a structural wall between two rooms.
We told them that they should, and the customer then went on to explain that their builder had recommended a certain size of steel beam. On larger jobs we ask for some calculations from a structural engineer as we are not specialists in structures - but in this case we had gone to the trouble of having some safe load tables produced as well as installing some simple to use software to do simple beam checks.
This is not to design the beam but to check the size, etc. which the customer has provided us with. We appreciate that the cost of employing an engineer on this type of job can be more expensive than the job itself so we try and help the customer as much as we can.
With this in mind, the person on our helpdesk asked the customer about the span of the beam, the types of loads it was taking, wall, floor and ceiling and the spans of these elements. Our helpdesk surveyor then drew what he understood the customer was explaining, worked out some basic loads and checked the beam against our safe load tables and hey presto it worked! He then scanned it and emailed it to the customer to check the dimensions. It was that good that the customer included it as part of their application back to us.
Site visit sheds a different light
But then the other surveyor went onto site, and as he said, it just didn’t look right. The dimensions that the owner had given us were wrong. The span of the beam was smaller, but the spans of the floor beams spanning onto it were longer. When the surveyor went upstairs there was not only a wall resting onto it but also another beam going right into the centre of the span from another wall that had been removed. My surveyor asked to see in the roof only to find that it was a traditional cut roof, with a ring purlin with centre props taken down onto the brick wall which eventually went down onto the new steel beam.
The surveyor explained to the owner that the details that they had presented on the phone and subsequently checked before using them as part of the submission were not quite right, neither were the loads put onto it. The owner and builder agreed to hold fire until he had returned to the office and tried the beam again using the new dimensions and loads. However when he did, and checked it on our safe load tables it fell just over the wrong side of safe and my surveyor advised them to get an engineer in.
As I explained earlier, we are not structural engineers and although we have a basic knowledge of structures, the information we have is ‘belt and braces’ and if we check it using these it will work with a good safety factor. In this case it had only just failed and my surveyor was confident that a more specialist engineer would be able to prove it, but we needed to see that in black and white.
Although the customer wasn’t happy with having to pay for an engineer, I was pleased as my team had tried, twice, to get the beam to work without having to ask the customer to do this. As it was, the engineer worked his magic and proved the beam would work, subject to applying some restraints at the bearings. The customer did tell us that he had told us it would work in the first place, but would you have taken the chance?
- Building control surveyors can only check, you shouldn’t ask them to design
- Although experts in the regulations building control are not specialists in all areas
- Information we use to check always has a factor of safety over and above that used by “specialists”
Have a happy and prosperous 2009.