6.8 m RSJ for conservatory practical or not ??

[catdownunder]

Hi there just looking for any advice for a project I'm planning.

I'm looking to extend a lean to conservatory, with double glazed roof, by adding a 1750mm section of flat roof between the existing house and the start of the conservatory roof.

The conservatory is currently 2700mm deep and 6800mm wide, ideally I'd like to have to no central support pillar for the section of flat roof. Is anyone able to offer advise as to what sort of RSJ would be required, and what sort of cash I'd be looking at for the steel.

The flat section of roof will incorporate several double glazed skylights, which will obviously add to the loadings, these are being used in order to keep the structure classed as a conservatory, 75% minimum transparent roof required.

Just looking for general feedback as to how practical the idea is at this stage, I realise a pillar or two will make things a whole lot easier, but I'd much prefer the space to be unbroken.

Thanks in advice for your thoughts

 

[tony1851]

Structurally it's do-able, but you would need a heavy beam - something like a 254 x 254 column section. Your supports either end would need to be substantial, possibly steel columns rather than supporting on remaining brickwork.
But if opened up, would the conservatory still comply with Part L?

 

[noseall]

A flat roof annexe full of roof lights sounds horrendous.

 

[catdownunder]

Thanks for the reply Tony, I was looking at the 305 X 165 40 UB, it seems I can get one for delivered for slightly over £300 which seems reasonable. I assumed a deeper beam would be better suited as there will be minimal side loadings, but don't really know too much about this stuff

As far as I'm aware part L won't apply as the structure will still be classed as a conservatory, the beam isn't to open up into the house, the existing external doors will remain in place, it will be situated where the new flat roof meets the pitched conservatory roof.

I've yet to lay the slab, it will be laid to exceed current building regs, I've got planning approved for an extension which will follow further down the track, by getting BC to sign off on the slab I don't have to worry about the permission expiring in three years time

I'm sure it will be easy enough to build some columns into the walls to support the beam, the footings are going down 100cm so shouldn't have an issue.

 

[catdownunder]

A flat roof annexe full of roof lights sounds horrendous.

Couldn't agree more, they are only there to allow me to get the conservatory certified

They'll be recessed and have solid sliding blinds underneath, similar to those found on aircraft windows, I'll frame them with some form of indirect lighting to disguise their true purpose

lighting

• catdownunder
• 9 Aug 2013
• 1

I'm only going down this route as to get the look I want certified as an extension will cost a small fortune in triple glazed units, bloody greenies [/img]

 

[tony1851]

I was looking at the 305 X 165 40 UB,

Forget that.
Deeper beams do generally help reduce deflection, but on that span you will also have to consider buckling. That beam will buckle sideways long before it reaches its maximum permissible bending stress.

 

[jeds]

If I'm picturing it right the beam will only be taking a bit of conservatory roof and a bit of flat roof. If so the beam might be a lot smaller than you are thinking. To know for sure work out the loads and get it calculated.

 

[tony1851]

If I'm picturing it right the beam will only be taking a bit of conservatory roof and a bit of flat roof. If so the beam might be a lot smaller than you are thinking. To know for sure work out the loads and get it calculated.

You could be right there. I was just assuming it would be taking the back wall of the house; I probably misunderstood.

 

[indus]

As mentioned it doesn't sound like your beam will be taking that much load.

I've just had a beam fitted that was about 6.3m but it will be the back wall of the house. It was a 203 x 203 x 86kgs.