Timber Roof Spread 6

[damo74]

Hi all.

I'm designing a timber cut roof with a lack of triangulation. It typically consists of 2 rafters supported at the feet on block walls. There is a raised collar tie about 1/3 depth from the ridge. There is no ring beam at eaves.

Has anybody any experience in what to check for this case?

 

[damo74]

Thanks valleyboy.

Yes I had considered using an eaves beam but I was trying to avoid it.

My panel is working suuported on 3 sides with a line load.

But for future reference, the ply web beam sounds interesting. However I don't know how it would be constructed or exactly in which plane it would be placed in. Could you confirm?

 

[valleyboy]

The ply-web beam solution is constructed within the depth of the rafters, between the wall plate and the point where the collar tie intersects the raters. The top and bottom boom are formed from noggins which run between the rafters. The upper compression boom is cut to tightly bear onto the face of each rafter, whilst the tension boom is connected to each rafter with a truss clip or similar engineered fixing to maintain continuity of the lower boom. Complete area of outer face has a ply covering before the battens are applied, and the inner face has a ply sheathing applied before the plasterboard soffitt cladding.

The ridge needs to be propped during construction, and the supports need to be robust enough to resist the reaction from the beam.

For your solution above, does your masonry panel work supported on three sides with external wind pressure and internal suction?

 

[damo74]

That's a good idea for future options valleyboy. Thanks.

I've checked the masonry wall panel with external wind suction as this will give worst case loading when added to the outward roof spread. This idea works fine.