Help! Structural engineer/Building control issue

[Gretchenwilson]

We recently bought a house which had already had a single story extension at the back of the house. This extended both the kitchen and dining room into longer, narrow rooms, so we have had the connecting wall knocked down, but have left the existing, vertical steel from the extension in place.

The structural engineer advised that no part of the wall was was load bearing as the walls on the floor above were not directly in line with the walls below. The drawing from the SE stated that we would require an extra, smaller steel to be attached to the existing vertical one, as well as a horizontal one to support the roof of the extension.

Building control are now advising that we should have had an extra steel fitted onto the exterior wall of the extension (between a window and patio doors). This would mean a kind of 'n' shape of steel with two vertical and one sitting on top of them. Which seems maybe a bit excessive for a non-load bearing wall, with nothing above it but the flat roof of the extension?

I'm pretty clueless though, so wonder if there's anyone who might know a bit more about these things?

It's a bit difficult to picture what you are trying to describe, but the first question is, if building control are questioning your engineer's advice then you need to go back to the engineer!

The 'n' shape you describe may be required if there is a large opening and it needs extra stability. Sometime people call them goalpost, or portal frames. The other common reason for needing posts is if the masonry walls cannot take the load from the beam (but that would be unlikely for a single storey extension).

"Which seems maybe a bit excessive for a non-load bearing wall, with nothing above it but the flat roof of the extension?"

I think that part of the extension takes a huge amount of the load - it kind of spreads out. Definitely go back to your engineer.

It doesn't help that the various people we've spoken to in building control don't seem to agree on this! Have spoken to the structural engineer so will see what they come back with. Thanks for your help

The SE is the designer, building control should be checking his work. If they have issues you should get them to discuss directly and the SE can justify his design. It's not really up to the council to do the structural design.

The Council are not qualified to do the structural design and should go back to the SE with any queries. Building control officers have not actually done the calcs and may not understand the design. Between the two of them, they should be able to resolve a fairly basic design!

I guess it's for racking as the original walls, even though not load bearing, provided diagonal bracing.
The engineer that provided your design should deal direct with building control for clarification.