Ridge beam positioned over window opening

6 Jun 2007
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United Kingdom
The SE specified the UB that will form the ridge beam for the roof on my new extension. He also specified a standard block sized padstone for it to sit on with the 2 courses underneath the padstone to be 'beefed up' with 7N blocks/bricks (the rest of the internal wall is in 3.6N blocks).

What he didn't know at the time was that there will be a window opening below the beam with only 300mm between the bottom of the beam and the top of the window lintel. He's now on holiday.

The sketch below shows how the roof will be supported.

The next sketch shows the position of the window opening in relation to the ridge beam. The ridge beam is a 178x102x19 UB. The lintel is a Catnic internal partition/loadbearing wall lintel (steel box type: CN5XA) 1200mm in length spanning a 610mm opening, the SWL is 29kN. I have already bought the lintel.

My question is, using the strength of blocks/bricks in the positions shown, is the lintel adequate? I'd be grateful for any views/advice. Thanks
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Replace those 7n bricks with a concrete lintel which is longer than the opening width
as the window opening is only 610mm, then maybe this could be dealt with by spreading the load with say concrete lintels beneath the padstones instead of masonry?


where is shytalks?

it is a vulnerable location though. any window at this point in a gable end will render this part of the gable rather weak.

mind you, there is a lot of lateral restraint handy! :LOL:
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I can't see that the ridge beam carries any real load does it? The rafters lean on each other and on the purlin.
I can't see that the ridge beam carries any real load does it? The rafters lean on each other and on the purlin.

i think it maybe a restraint issue due to the lack of joists maybe?

vaulted or raked ceilings (joistless) use a steel ridge as a remedy for spread.
By minimising vertical deflection at the ridge, the horizontal thrust at the eaves is also significantly reduced/removed
That Catnic is fine. There won't be much of a reaction from that ridge beam, certainly not anywhere near the swl of the lintel. You don't need any more lintels over the top of it.
I can't see that the ridge beam carries any real load does it? The rafters lean on each other and on the purlin.

Bowness is right, but the other slope purlins are placed vertically, with the rafter birdbeaked over, so there would be less thrust at the eaves anyway; however, without the ridge beam, the slope purlins would have extra load on them, so presumably the SE put it in to keep the sizes down.

Without a ridge purlin, the horizontal and vertical reactions from one rafter resolve into an axial load in the other rafter, which in turn resolves into horizontal and vertical reactions at the support. So, if there was no intermediate slope purlin and no ridge purlin and the rafter spanned down to the eaves, that is why it would want to spread laterally.

Anyhow, that lintel is fine :)
Thank you very much. I appreciate all your advice, it's especially good to hear some of the thinking behind it too.

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