roof construction

[brianjama]

can any one tell me were i can view a detaled site showing the desgine of
a timber built edwardian roof with hippes and vallyes. need to see the fixing point on each corner awere of the birds mouth connections each
side but not sure of each corner point. many thanks.

 

[noseall]

are you referring to the diminishing rafter (jack rafter) splayed cuts, that join the hip rafter?

 

[carpenter les]

i think he means where the hip rafter meets the wall plate !!

 

[noseall]

if you are referring to the hip rafter and how it joins both the wall plate and the ridge board, then i think i understand.

the hip rafter is set at a completely different pitch to the rest of the rafters. it is shallower. therefore the top cut and the birdsmouths cannot be patterned from the regular rafters.

we use trial and error to achieve this cut. just remember though, the distance from the wall plate to the ridge is constant, so try and apply this measurement first and work from there. you will waste less wood.

 

[joe-90]

I think what he is aiming at is that the birdsmouth cut in the side rafters places the weight of the roof in a straight down path rather than pushing outward on the walls (although the joists tie in these rafters anyway).

In the corners there is no birdsmouth cut so the forces are outward (splaying out the walls). Does he mean the small tie-beam which goes at 45 degrees to the hip rafters across the corners? Can't remember what it is called.

BTW one of the best ways to see how older buildings were constructed is to look at photos of war where a house/building has been blown apart. It's like looking at a cutaway.

 

[steviec]

the tie beam which goes 90degs to the hip is called a "dragon tie"