Steel Frame supported on a Pad Foundation

[djwhite04]

Hi,

We have had a structural engineer advise that as we are opening up the back of our house by some 6 meters we will need to support the load by having a steel frame that is supported on a pad foundation at each end of the opening to support the overhead steel. This sounds very complicated and potentially very expensive can anyone help me to understand if this is straight forward for a competent builder to do and if it is an expensive part of the build?

Appreciate any advise that can be given.

Thanks

 

[tony1851]

What the engineer has designed for you is a 'moment frame', aka a goal post. These are usually incorporated when a large part of a wall is removed and when overall stability of the building might be an issue.
Unfortunately they are relatively expensive in terms of the additional steel columns and extra fabrication work (welding and drilling for bolts etc).
Some builders suggest putting brick columns at each end of the beam instead of steel, but don't be talked into this; the steel columns are there for a reason..

 

[^woody^]

I think these are a modern thing designed to cover the engineers insurance, more than anything else

 

[tony1851]

I think these are a modern thing designed to cover the engineers insurance, more than anything else

You may well be right on this in a lot of cases but it can also been down to how hard the SE is prepared to work.
When the opening is >3m wide, or takes up >2/3 the overall width of the wall, it goes outside the recommendations in AD A. In these cases, the inspector will often ask for lateral stability calcs to prove that the building will still be OK under lateral wind load.
Depending on the configuration of remaining walls, span of floor joists etc, it is often possible to prove it will be OK by doing more extensive (and therefore time-consuming) calcs. However, a lot of SEs won't be bothered and just do standard details for a moment-frame.
Having said that, a 6m span in the OPs case is long, and there may be circumstances in this case which warranted a frame.