Roof beams, why max 5 degrees in the table?

[Bob_the_builder]

As the title says, why do the sizing tables for roof beams in one/two spans state that they apply to a maximum of 5 degrees of slope? If I want 14 degrees, the snow load should be less, right? Does any other load increase?

 

[bjornligan]

14 degrees get longer along the same width between the walls

 

[Bob_the_builder]

Well, indeed. That might be the entire answer. At 4 m width, the diagonal length increases (if I'm calculating correctly) by 11 cm when going from 5-14 degrees.

 

[Bob_the_builder]

Don't know why the thread got double posted...

Wild guess - the measurement L is given in the horizontal plane. If the angle becomes larger, the length of the boards then becomes so much longer than L that the underlying calculations don’t hold.

 

[ljungpiparen]

Where did you find that table? There is usually a set of conditions for the tables, maybe it says there why it is the way it is.

 

[pjkw]

It can't be as simple as the calculation only applies up to 5 degrees? After that, a different table applies...

 

[Bob_the_builder]

No, it doesn't say why. The table is from Svenskt Träs "Lathunden". 5 degrees is a very small slope. Feels more like a special solution than a normal construction in 2016. There is no other table published.