A reader's Roofs and roofing question: Roof load?

Peter M,   from   Adelaide : Australia   had this roof load question.

Hi
Thanks for your website. I live in a timber framed house built around 1920.

Between your website and my Readers Digest DIY manual I have (1960) I have worked out I have a hip roof on my house. We have had termites and I want to remove an internal all so I am interested in understanding how load is transferred into the walls. It looks to me like a hip roof transfers all the load to the external walls. There is no load transferred to internal walls.

OR is it not that simple... Thanks

Bill's answer

Peter, rarely is that simple unfortunately.

Roof load -A cross section through a traditional roof.

• So if the house was built in the 1920's (pre gang nail trusses) then it may look something like this.
• Unless it is a very small house, the rafters and the hips will have support from under purlins.
• These under purlins do not have to be really large and expensive in an ordinary house, because they tend to get propped here and there mid span by struts which sit on internal walls.
• Peter you have to go into the roof space and locate the wall that you want to remove.
• If it is helping to support a purlin or a hip then you need to replace that support in some way.
• It is usually no big deal in a timber framed roof.
• It gets tricky if the wall is supporting another floor of course.