How do you mean? In another thread - you might not have seen it - Ibby says he wants a full width dormer, so how do joists help
RSJs - Ridge beams
- Thread starter ibby
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That may be a slight possibility if all the rafters and joists form a neat triangle, but when one or both sides of the roof are cut to form the dormer, the loadings change (triangle is broken) and the ridge needs support
Fair enough though...if the dormers were small and there was room to have rafters in between and either side of the dormers, then joists will tie everything together and triangulate the structure.
But if you click here, it shows what Ibby actually wants to do, and I can't see him doing it without a nice big steel section in the ridge.
But if you click here, it shows what Ibby actually wants to do, and I can't see him doing it without a nice big steel section in the ridge.
I'll answer questions and criticism in a moment, but first i'd like to say that this thread has gone from apparent lack of info. to confusion. How was i, or any other ignorant poster, to know that there was a parallel thread?
I've answered in good faith with the info at hand, and i'll continue on the basis of my assumption that i'm dealing with a cut-rafter, pitched, dormer roof.
That is, a pitched, dormer roof that intersects the main roof plane, not shed or multiple dormers - or intersecting dormer ridge and main roof ridge (because, in my experience, high, intersecting dormers are frowned on by planning.)
I've answered in good faith with the info at hand, and i'll continue on the basis of my assumption that i'm dealing with a cut-rafter, pitched, dormer roof.
That is, a pitched, dormer roof that intersects the main roof plane, not shed or multiple dormers - or intersecting dormer ridge and main roof ridge (because, in my experience, high, intersecting dormers are frowned on by planning.)
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Yea but if you read the parallel thread you'd know he wants to keep it PD! Where's your crystal ball?
Apologies Tim, I posted in the mistaken belief that everybody else reading the thread were as enlightened as me as to Ibby's plans.
Almost all full width dormers will require steel unless it's a very narrow house, although you are correct in saying that most other types of dormer conversion can be done without steelwork.
Almost all full width dormers will require steel unless it's a very narrow house, although you are correct in saying that most other types of dormer conversion can be done without steelwork.
woody,
In what sense do you mean "upgrading"?
A ridge beam,extending from a dormer face post, back to an extended double valley and an intersecting double valley point, will often take the load - other framing arrangements using headers and doubled common rafters etc. to support the ridge beam at the main roof plane, rather than extending the valley, might be more suitable. In my experience, none of the above require steel. Given that it's some time since i last did a loft conversion.
In loft conversions: timber purlins, introduced or present, may be supported by stud framing when struts and supports are removed. Loft partitions may also take some load.
Main ridge board/beam work moves us into a different area.
The ceiling joist business can be resolved in many ways, but joisting as far as possible on the top plate and then being creative, going up the slope will provide integrity and tie-in. Framing a dormer without joisting is too much to describe without pics. Again, i've not had to use steel.
In what sense do you mean "upgrading"?
A ridge beam,extending from a dormer face post, back to an extended double valley and an intersecting double valley point, will often take the load - other framing arrangements using headers and doubled common rafters etc. to support the ridge beam at the main roof plane, rather than extending the valley, might be more suitable. In my experience, none of the above require steel. Given that it's some time since i last did a loft conversion.
In loft conversions: timber purlins, introduced or present, may be supported by stud framing when struts and supports are removed. Loft partitions may also take some load.
Main ridge board/beam work moves us into a different area.
The ceiling joist business can be resolved in many ways, but joisting as far as possible on the top plate and then being creative, going up the slope will provide integrity and tie-in. Framing a dormer without joisting is too much to describe without pics. Again, i've not had to use steel.
You won't have a ridge beam at the moment. You'll have a ridge board, which is designed to do nothing more than keep your rafters at equal spacings. It's not designed to suuport the rafters in any way as they become self supporting once triangulated by connecting to the ceiling joists.
Well he thinks he is!I am learning alot here
It looks really thin to me, when I looked at it,
Maybe a 1x6 or 1x8.
I am using the wrong terms - I am a novice
Well he thinks he is!I am learning alot here
Its too much information
Yup, that's a ridge board. Once you take away the rafters on one side and replace with a full width dormer, you lose the triangulating effect. So you will need a steel beam.
And going by your measurements in the other thread, it'll be something pretty big, like a heavy 203 UC or a 305x165 UB.
Been told I would be looking at
250x150 Purlins.
So I assume the Ridge would be a similar size, if not smaller.
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