Timber Roof Struts

[cherie]

Hi, I am a new building student, currently doing an assignment for timber framing. Can anyone tell me why timber roof struts are placed on an angle ? I know you can have vertical roof struts but I need to know whats the purpose of a strut on an angle called 'perpendicular struts'. I've searched the web for an answer but cant seem to find an explanation. Many Thanks!

[DvdHntr]

They are perpendicular to the rafters for easier installation.

[thebuildingsurv]

You put them to wherever you have a wall or support underneath

[bitingmidge]

What the Building Surv says, and a bit more.

The struts are there to hold up purlins, which in turn hold up rafters. The purlins have to be spaced at mid or third span (or whatever spacing is required to support the size of rafter), and there isn't always a wall in a handy position below, so they end up at an angle, not necessarily perpendicular.

There aren't too many framed roofs being built today, but the best way to understand how they work is to actually crawl into one, and follow every stick to its natural conclusion.

Don't try to learn it from a book, or by asking questions on the internet. Get up into the roof of an old house and OBSERVE for yourself.

When you can see it from inside the space, it's all very clear.

Cheers,

P

[les88]

The struts are placed so as to form a triangle if they are perpendicular then they are not at the correct angle
les