Ridge beam abutment to existing wall


7 Aug 2006
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United Kingdom
I am about to build (/have built) a single storey extension, with a 22.5 degree pitched roof abutting the existing house such that the ridge comes (just) below the first floor windows. Building Regulation Approval has been granted. The roof will be open vaulted, spanning between the ridge beam and wall plates. The ridge beam is supported by the end gable and an intermediate wall, but the drawings don't show how it is supported/fixed at the house wall?

1. Should rafters be fixed to the house wall and notched to take the ridge beam? If so, should the ridge beam just be nailed or maybe bolted to them.

2. Should the ridge beam be taken through the outer skin of the house wall (please no!), or maybe supported by a joist hanger, or nailed to a timber support fixed to the wall?

3. If the latter, should the first rafters be fixed to the wall or just to the ridge beam? At the other gable end, I assume the rafters would not be fixed to the wall (but a flying rafter will be built on noggins through the wall).

I would be grateful for any advice.


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If you have an engineer or architect its down to them to specify fixing details for structural items.
Sorry for slow response - been away from PC fro two days!

My architect technician is waiting for the engineer's response to his design, which has a wooden ridge beam (50*200 I think, but I've not got the drawings to hand right now), and no details of its end support. We were expecting Building Regulations approval to wait for or be subject to the engineer's calculations, but approval has been given straight away.


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50x200mm sounds a bit lean, but that would depend on the span i guess.

usually if there are no ceiling joists (open, vaulted type) which in turn means no way of resisting roof "spread", then a steel or a very hefty wooden ridge support is necessary to help prevent spread.

this ridge element will have to be supported by 100mm of maonry at each end.
I agree. I have designed hundreds of these and it is usually a fairly substantial steel beam built into the house wall.

(does depend on span and roof covering though)
Thanks for your help, I'll talk to the engineer when I get his calcs.

The ridge beam specified by the architect technician is actually 225*75, but we are still awaiting the engineer's confirmation. The ridge beam spans 2.8m, and the rafters span 4.1m at a 22.5 degree pitch.

I could include short tie beams between the rafters just below the ridge beam, but we want the open vault feel (even if the overall height will not be great (given the shallow pitch).

Thanks again

I would have thought ,to prevent roof spread .rather than the rafter' s birds mouth sitting on the wallplate this would have to birds mouthed over the front edge of the wall plate ( notched over the front of the wall plate)
in order to resist spread, the ceiling joists are essential regardless of the rafter/ eaves/ wall plate situation.

remove the joists and you need to find another way of preventing spread.

hence, a built in steel or large section timber ridge element.
noseall said:
in order to resist spread, the ceiling joists are essential regardless of the rafter/ eaves/ wall plate situation.

remove the joists and you need to find another way of preventing spread.

hence, a built in steel or large section timber ridge element.

I have never done a gallery roof like this,well to tell you the truthI've only ever done one.
I cannot see how a large steel/timber at the ridge would help that much to prevent spread any more than having a normal ridge ,given that a ridge is only a fixing board what ever the size.
PS I hope that I have not hi-jacked the post,as I think my question ties in with the original post :)
A ridge beam is the standard method of preventing roof spread in an open gallery style roof. The idea is that the beam is built into the gable ends and the rafters hang from the beam - thus preventing spread.
Looking at what size of ridge beam i require for my sunroom extension. Want to vault ceiling.

4x3m ext, walls 2.4m high

span 2.4m betwwen wallplates int
lenght of ext 3.75m int
rafters 100x47, 400mm centres
angle 35deg
area of roof approx 18m2
concrete roof tiles 50kg/m2
live load been told 0.75 - 1 kN/m2
location 10miles from Belfast

any help appreciated
The rafter span is 4.1 ? is that overall wall to wall or the span from wall to ridge ?

My initial thoughts are that based on the span of the ridge, a heavy piece of steel may not be required. It just depends on the overall building span.
The rafter span is 4.1 ?

Where does it say that in the post chickenlips?

OP. Your span is always measured overall plates in roofs.Confirm that your span is 2600 overall plates
Regards oldun

Length of rafters is around 1.8m to birds mouth.

Internal width is 2.4m, wall plates on inner skin.
Overall width / span from outside of wall plates is 2.6m

Hoping a 9x3 or similar would be enough?

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