6 metre Lintle / RSJ advice please?

[hammerswinger]

Hi,
we're in the first stages of planing for a single story extension to the rear of the house, at present we have a couple of proposals for the layout of the extension one of which entails a 6 metre RSJ / Lintel being used right across the rear of the house to open it up to the new extension.

I fully appreciate that the exact specifications of the steel will be determined by a Structural Engineer however I would just like a rough idea of what sort of beam we will be talking about (approximate dimensions) and what sort of price?

As you can see from the picture I have marked the approximate location of the steel.
As far as I can see the design of the roof of the house is such that the gable ends appear to support the majority of the roof weight.

Thanks.

 

[^woody^]

A 254x 254 column.

 

[hammerswinger]

So something like a 254 X 254 X 73KG ?

Any idea how much I could expect to pay for a 6 metre length of one of those, as I can't seem to find any prices on the internet?


Thanks

 

[geraint]

A 254x 254 column.

why that big....

 

[^woody^]

It's the first thing that came into my head!

Nah, we did one a while ago and it was just over 6m, but come to think of it it had a point load too from another beam

A 203 deep beam may not suffice, so perhaps 2nr 254x102 ? And two will be easier to lift than one monster

Cost? £300 each or so?

 

[geraint]

It's the first thing that came into my head!

Nah, we did one a while ago and it was just over 6m, but come to think of it it had a point load too from another beam

A 203 deep beam may not suffice, so perhaps 2nr 254x102 ? And two will be easier to lift than one monster

Cost? £300 each or so?

i personally do not like the column sections... would much rather see and fit two beams. so far better in support and even better to get the buggers in..... but they always specify two different sized sections....

worse than architects.... no thought....

 

[Static]

So something like a 254 X 254 X 73KG ?

Any idea how much I could expect to pay for a 6 metre length of one of those, as I can't seem to find any prices on the internet?


Thanks

Probably a 89kg size for that kind of span.. would need to be spliced..
You will have to phone fabricators for quotes..

2 beams bolted together may end up deeper and more expensive.. but easier to put in place.. may end up with something around the 406mm deep beam size..

All assuming that steels supports first floor..

If you want to cut cost, then introduce a mid span column..

 

[hammerswinger]

Hi,
Thanks for all of the advice just trying to get an idea of what would be involved if we go with the 6 metre beam.

Yes the steel will support the ends of the joists for the 1st floor.

A 406mm beam..... that would hold up a sky scraper, don't really want a mid column as that would spoil the layout.

Thanks.

 

[jeds]

I recently did a similar one at slightly less span (5.6m) but had two other beams loading onto it. They came out at 2nr 254x146x31 beams bolted together. Without the two point loads they would have been well over the top.

Axial loading and deflection isn't the main issue though. What you need to be careful of is lateral wind loading. You'll probably be looking at a frame to take care of that.

 

[hammerswinger]

The rear elevation of the house faces south, the wind always seems to hit the west gable of the house.

What would a frame involve?

We have 2 possible layouts for the extension, we prefer the opened up version but this will need the 6 metre beam, I'm just trying to figure out how much extra this will add to the cost, if it starts to get silly we will just have to go with the other option.


Thanks.

 

[jeds]

A frame consists of a beam placed on columns to form a goalpost. The joints need to be sufficiently rigid to overcome any overturning effect. The columns might need their own foundation - i.e. a pad. But that depends on your existing foundation etc.

If you remove the whole wall you really need a proper design. You'll need calcs for building regs anyway so you might was well start talking to a structural engineer.

 

[hammerswinger]

Hi,
Thanks for the explanation.

The architect has had a look at the house & he didn't mention anything out of the ordinary regarding the beam when we explained the open layout so hopefully it won't need a frame but I guess that will be down to what a SE says.


Thanks for the advice.

 

[geraint]

So something like a 254 X 254 X 73KG ?

Any idea how much I could expect to pay for a 6 metre length of one of those, as I can't seem to find any prices on the internet?


Thanks

Probably a 89kg size for that kind of span.. would need to be spliced..
You will have to phone fabricators for quotes..

2 beams bolted together may end up deeper and more expensive.. but easier to put in place.. may end up with something around the 406mm deep beam size..

All assuming that steels supports first floor..

If you want to cut cost, then introduce a mid span column..

you are definately taking the **** a 406 beam..... twice...

go back to school

jesus...

that would hold the whole street up...

 

[geraint]

A frame consists of a beam placed on columns to form a goalpost. The joints need to be sufficiently rigid to overcome any overturning effect. The columns might need their own foundation - i.e. a pad. But that depends on your existing foundation etc.

If you remove the whole wall you really need a proper design. You'll need calcs for building regs anyway so you might was well start talking to a structural engineer.

Axial loading and deflection isn't the main issue though. What you need to be careful of is lateral wind loading. You'll probably be looking at a frame to take care of that.

glad you know what you are talking about..

nothing....

 

[wavetrain]

As far as I can see the design of the roof of the house is such that the gable ends appear to support the majority of the roof weight.

What makes you think this?

The gable ends support little weight if it is a typical roof construction. It is the other 2 walls where the weight is transferred due to the coupled roof design.

Therefore your steel beam would need to support half of the total roof weight.

But as other posters have already mentioned, there are other factors to stop your house from collapsing, I advise to stop designing your extension and goto a SE and find out first what is possible, then continue with the non structural details yourself.

Also, house value is dependent on the number of rooms in a house. Jeff Howel who writes in the Telegraph argues that grand open plan designs can lower the value of the original house.

To side track for a moment, there was an amazing Channel 4 Grand Design where the kitchen was in the centre of an open plan oak round building if my memory serves me correctly. kevin asked the woman owner about cooking smells getting around the house. She replied by saying it would not be a problem as they would just dissipate into all the rooms!! Glad I don't live there.