Residential tied roof

[MyCupboard]

I have been in residential structural engineering for about 8 years. I know there are some things that are a “big deal” and other things that can SOMETIMES be approved simply because of redundancy and oversimplification of the system.

Tied roof concepts tend to be a good topic with varying opinions. This specific question is related to when roof rafters (sloped) and ceiling joists (flat) meet at a flush bottom beam.

In typical wall details for the house, the rafter laps the ceiling joist and is fastened accordingly to resist the thrust. So where they come together at a flush beam I just thought they would align the beam appropriately so that they overlapped, get fastened, and both hang off the beam.

During a frame walk today, I came across this little detail. I’m curious to hear everyone’s thoughts. Mine range from (there is still a bunch of nails scattered into the lapped portion), to (should I have called out separate hangers because of the sloped condition and flat condition?), or (couldn’t they have located the beam so that there was more of a “seat” at the bottom of the roof rafter that could then hang into the beam with the double hanger?

I am by no means an all knowing expert, but considering this builder is extremely confident and proving to be not at all competent, I’d like to get some wisdom before I address this line item.

For clarification, they scabbed an angled member to the side of the ceiling joist to create a flush bearing condition at the hanger. That’s my guess at least.

 

[MyCupboard]

I would detail it as well

 

[phamENG]

That's how I would do it, too. Just have to make sure the seat in the rafter is cut so it's fully supported. It takes a framer that's paying attention.

 

[MyCupboard]

And there you are! The builder met that requirement!

ok, so in short - you are good with the way this is installed? assuming they met the fastening criteria, hanger spec, and member sizes? i'm curious if the odd pointy bearing condition that the rafter is in has anyone concerned? as opposed to the detail i mentioned just above this.

 

[Eng16080]

That detail is fine, but it only works geometrically if either:

1. The roof rafters can be lowered, or
2. the ceiling beam is shifted to the left

 

[Eng16080]

ok, so in short - you are good with the way this is installed? assuming they met the fastening criteria, hanger spec, and member sizes? i'm curious if the odd pointy bearing condition that the rafter is in has anyone concerned? as opposed to the detail i mentioned just above this.

I would check the two load paths mentioned in my post above, and if both are satisfied, I'd probably be ok with this. I say probably because I would give it a little more thought on a real project than I'm giving it here in this forum.

 

[phamENG]

i'm curious if the odd pointy bearing condition that the rafter is in has anyone concerned?

You have a few different things going on. Looks like you really don't have bearing - too much gap between it and the scabbed on 'shim.' But you do have the fastening to the CJ and the toe nails from the hanger into the side of the rafter. If you can't satisfy yourself that the nails can do the job (the face nails handling both the vertical load and the horizontal thrust), then I'd say shimming or otherwise filling that gap to create a bearing condition would be the way to go.

 

[MyCupboard]

You have a few different things going on. Looks like you really don't have bearing - too much gap between it and the scabbed on 'shim.' But you do have the fastening to the CJ and the toe nails from the hanger into the side of the rafter. If you can't satisfy yourself that the nails can do the job (the face nails handling both the vertical load and the horizontal thrust), then I'd say shimming or otherwise filling that gap to create a bearing condition would be the way to go.

This is my answer that i am giving the builder. This was my main concern, expressed in a cluster$@%& longform, haha. Thank you.

 

[phamENG]

This is my answer that i am giving the builder. This was my main concern, expressed in a cluster$@%& longform, haha. Thank you.

Curse of the engineer.

Glad to help. Good luck.

 

[jdgengineer]

I would normally detail this condition and I like the last image that was posted. I think the ceiling beam is in slightly the wrong location from optimal in the first image and this is corrected in the last one to allow for a proper seat cut on the rafter. I would have liked to see the ceiling beam pushed to the left in the original photo by a few inches so that the rafter has a proper seat in the hanger and you wouldn't need the scab block at all.

Without a detail I think it's hard to communicate the importance of the geometry.

 

[jerseyshore]

That detail is fine, but it only works geometrically if either:

1. The roof rafters can be lowered, or
2. the ceiling beam is shifted to the left

Agreed. If the roof slope doesn't work then there is only so much they can do.

I have the same exact detail as the OP in my master bedroom. It's the most common way I've seen this framed out.

Normally I wouldn't detail it as long as I knew the nails at the laps were sufficient to resist the thrust at the heel.

I do detail these connections if it's not a simple lap though. Or if the beam is interrupting the ceiling joist/ rafter tie in the middle somewhere. I never want weak axis bending in these beams and Simpson is clear that their hangers are not tested for "withdrawal". Basically anything that requires a non-standard load path I'll detail.