design for 7.5m steel with cross-beam

[Darola]

0E095C5B-C3F7-40B0-B17F-27A3FF537F39

• Darola
• 30 May 2020

Internal cross-beam

4CC13D3B-9DD9-424E-B338-926E817CCED6

• Darola
• 30 May 2020

Rear view to extend - with single story.

Hi folks.

I’m looking at a new project to extend the back of our house with a single story open plan kitchen/family room. Currently the space is half kitchen, going into a “family room” area that has a galleried landing (see photos). To open the back of the house up it requires a steel beam just shy of 7.5m, that would also have to support a cross beam for the internal wall at 90 degrees.

The architect is scratching his head a bit and the structural engineer is dragging his feet (problem with mates rates!). My question is - is this doable!? Or should we just accept the nasty compromise of a mid-point supporting pillar?

 

[freddiemercurystwin]

Everything is a doable with enough cash, 7.5m span will be something like a 350-400 deep beam even without having to support the crosswall (which appears o be taking the roof too) so could end up pretty big. Even if you get it flush with the 1st floor flush there'll be a downstand. Might need a column each end too which might mean a pad foundation for each.

 

[Darola]

Thanks for the response. What do you mean by downstand? Was expecting to put in a column either end, plan was to build them out so the internal wall could still be flush. Happy to sacrifice a flush ceiling if we can get it open plan. Should have said in my original post I’m aware that you can get anything if you pay for it. Just for the steel work and related building and fitting to get it in, is £5k a reasonable budget?

 

[tony1851]

With respect to FMT, I suggest that could be done with one of the 254 x 254 beams, even allowing for the point load of the incoming beam.
Whether or not it needs posts for lateral stability depends on the overall plan of the ground floor, and the disposition of other load-bearing walls.
To accept a post to split the span would be a design failure.

 

[freddiemercurystwin]

There's no respect on this site!

 

[Darola]

The SEs calcs have come back (see pics) and the good news is no pillar. Compromise so far is we have to work with 440x440 block piers, which the architect said could be set into the wall, so would be protruding circa 300. Based on the experience you guys have would steel piers be an option to reduce this? It already requires additional foundation work, so how much extra would we be talking to use steel? £100’s or are we moving into 4 figures?

 

[garyo]

I don't know the answer to your question re the goalpost frame, but that's the kind of compromise that you'll be staring at every moring over your frosties. If it was me I'd find a way of using steel posts even if you have to dig out metre cubed post foundations.