Roof Spread Hip End 1

[Contraflexure74]

Hi,

I have an interesting scenario where the client wants a hipped end extension roof but wants a vault ceiling effect. See sketch attached. I'm obviously concerned about roof spread.

He wants to maintain the vault around the corner which is a lean to roof effectively. I'm not too concerned about the lean to section but I am concerned about the hip end.

Anyone come up with something clever to solve this before? Thoughts welcome, roof lights can be moved/removed.

 

[CANPRO]

The walls can only spread out if hip rafter deflects downward - provide a structural hip rafter, sized to limit the wall spread.

 

[Canuck65]

If you connect a structural hip rafter to the stub of a ridge that is shown on your sketch, it could still deflect downward as the roof rafters that tie into the end of the stub of the ridge are also cathedrale.

One option would be to alter the roof framing slightly so that the structural hip rafters tie into the existing wall of the house, i.e. eliminate the stub of a ridge board. As long as the existing wall can support the vertical loads, it should be fine.

Another option that would be more work and only rarely done would be to specify a steel frame, with moment connection at the ridge where the roof rafters that support the end of the stub of the ridge shown in your sketch. Not my preference, but doable.

Your wall lengths are relatively short. Your roof will not spread if A) the ridge cannot move downwards, OR B) the top of the walls cannot move outwards. You could design the walls so that the top plates span horizontally and are tied in securely at intersections .... on second thought, this might not work for the wall shown at the top of your sketch ... maybe it can be detailed, maybe not

The lean to section should not be of any concern if the rafters are properly tied into the wall with a ledger.

Simplest by far is the first option, move the intersection of the hip rafters to the left, tie into the wall securely and size the hip rafters appropriately.

 

[Contraflexure74]

Thanks Canuck65. To move the hip directly onto the wall is a clever move. I will beef up the hip rafters to something substantial and bolt the wall plate to the top of the wall/steel head every 400mm centres. That should do the trick.