Why is my hip not in line with rafters both sides?

[pilsbury]

I’ve set my common rafters both sides. All nicely at my 40^ pitch. Just measured up and cut my compound mitre where the hip meets the ridge beam. But it seems like the hip joist can’t be in line with the rafters both sides.... if I set it level with one side of common rafters, it’s approx 1” higher for the other side.

Please tell me what rookie mistake I’m making.

 

[pilsbury]

The hip rafter is in line with the commons on the other side.

 

[noseall]

The outer edges of the hip blade are what the jacks line up with.

Therefore the point at which a 50mm wide hip blade strikes the ridge will seem artificially lower.

We cut a 45 degree splay, onto the recipient elements where the hip strikes top or bottom, if necessary.

We use two pairs of opposing jacks, one long pair and one short pair and butt them together (so that the compound cuts touch) to give us the top edge plane of the hip blade, then set up a line or use a straight edge. This then gives you something tangible to set up the bevel and take measurements in order to successfully and accurately do the top and bottom plumb and seat cuts for the hip blade.

We use the same two pairs of jacks to line up the hip whilst we trial and error it into place.

 

[noseall]

With a 50mm wide hip blade you need to imagine that if the jacks were to actually touch, they will meet at a point that is higher than the centre of your flat topped hip blade.

 

[pilsbury]

On a regular basis I get the feeling I'm out of my depth - usually once a day, sometimes more. After reading and re-reading your post, I get what you're saying (I think). The jack rafters in theory project past the top of the hip joist. Also setting up a couple of straight edges on each side seems a winner too. In the absence of any roofing skill or knowledge, this will let me work the hip into the right plane.

Just one bit I still don't get below - are you suggesting I cut a 45^ angle on my ridge beams at the corner where the hip will seat?

We cut a 45 degree splay, onto the recipient elements where the hip strikes top or bottom, if necessary.
.

 

[bobsuerita]

why is your rafter so far from the corner and centre of your hip needs to hit center of the corner not to one side as your creating a bastard hip unless it is 2 dif angles

 

[pilsbury]

why is your rafter so far from the corner and centre of your hip needs to hit center of the corner not to one side as your creating a bastard hip unless it is 2 dif angles

Rafter is not on the corner of the wall plate just because I was taking the photo with one hand whilst holding with the other - It made no difference to how the hip lay just for photo demonstration.

I do take your point about needing to hit the centre of the corners. I shall be setting up some straight edges tomorrow and will use this info.

 

[noseall]

Just one bit I still don't get below - are you suggesting I cut a 45^ angle on my ridge beams at the corner where the hip will seat?

If needs be, yes. We also trim the corner of the wall plate where the hip bottom strikes it.

 

[pilsbury]

Bang on chaps. Sorted. What fixed it for me was setting up a couple of guides - straight bits of wood laid across the common rafters both sides projecting to the corner where the hip lies. This then let me set it in the right plane both sides. I also had to chop the corner off my wall plate so the hip joist sat low enough.

I think I shall set up similar guides for the valleys.

Thanks again all for digging me out of a hole!

 

[chappers]

With a 50mm wide hip blade you need to imagine that if the jacks were to actually touch, they will meet at a point that is higher than the centre of your flat topped hip blade.

Yep the old way was to cut a backing angle on the hip rafter, once upon a time I could have probably told you how to work it out.
Now just use a flat hip rafter and work it out by trial and error/straight edges/dummy jacks too.

 

[Ian H]

Sorted.

Come on Pilsbury, you know the drill. Pics or it never happened!!!!

 

[pilsbury]

Where did you get that ridiculous saying from?!

 

[bobsuerita]

is your building inspecter happy about screws being used

 

[Ian H]

Where did you get that ridiculous saying from?!

Some drunken roofer/builder

 

[pilsbury]

is your building inspecter happy about screws being used

He saw the roof just over half done and didn’t mention it.