Pyramid hip roof framing - they say they do not need an engineer

[icebox14]

I live and work in Tennessee, residential plans are not required for permitting. We do require a scope of work but details are limited. Every residential build is different even on spec homes. I went to this garage 24x24 that had a scope of two garage doors 9x7. When I arrived there was only one garage door opening, if I remember correctly it was around 18 feet wide with two 2x10s or 2x12s for the header. The joists are 2x6's and span the entire 24 feet across the garage. The hip rafters are 2 inches smaller in depth than the rest of the rafters. I am thinking this is outside of the scope of the IRC but I know it will be a fight to prove that. I have never seen a build like this and I am under the impression that even if they put some support underneath the joists the tip of the roof is bearing too much weight for a couple of toenails between each rafter. Any guidance on what more I am missing? For reference this is a garage built for a pastor, paid for by the church, which in my area church's get a lot of leeway but this is way more dangerous in my opinion than the typical deck ramp they mess up that we are forced to ignore.

 

[bill1952]

It appears the rafters do not sit on the top plate?

Can't help but think hip rafters are undersized at 2" less than commons and jacks.

 

[TheCommish]

Needs help with soothing to tie the short ceiling joist across the building, possibly a bigger header

 

[e hilton]

The fact that it is built for the pastor should not be a factor unless it is on the same property as the church. I understand churches expect leeway, but if it’s on the lot with the house and that is remote from the church, it’s a separate parcel and could be sold to the public.

 

[BN4537]

Google says that area of TN has a population of a little over 6,000 people. To get along in an area like this, you are going to have to become good at figuring out how to fix stuff like this without an engineer, and being able to show people that the math doesn't math on these spans. You will need resources outside of the code, and you will need to know how to use them, and you will have to be able to articulate how you reach the conclusions you reach. You are going to need to be resourceful. A beam software like BC Calc is your friend. You can't just say it is wrong, you have to be able to say what it takes to make it right as an option to getting an engineer.

My opinion is that this could be made to work (mostly) prescriptively if rafter ties are installed perpendicular to the ceiling joists to keep the walls from spreading, collar ties are installed in both directions, and the ceiling joists spans are broken with LVL beams to span IRC. Garage headers to be sized IRC or LVL as the span may dictate. The lumberyard is your friend, or you can use BC Calc if you know what you are doing.

Hip rafters may need to get bigger as well. I would use something like this:

 

[BN4537]

Google says that area of TN has a population of a little over 6,000 people. To get along in an area like this, you are going to have to become good at figuring out how to fix stuff like this without an engineer, and being able to show people that the math doesn't math on these spans. You will need resources outside of the code, and you will need to know how to use them, and you will have to be able to articulate how you reach the conclusions you reach. You are going to need to be resourceful. A beam software like BC Calc is your friend. You can't just say it is wrong, you have to be able to say what it takes to make it right as an option to getting an engineer.

My opinion is that this could be made to work (mostly) prescriptively if rafter ties are installed perpendicular to the ceiling joists to keep the walls from spreading, collar ties are installed in both directions, and the ceiling joists spans are broken with LVL beams to span IRC. Garage headers to be sized IRC or LVL as the span may dictate. The lumberyard is your friend, or you can use BC Calc if you know what you are doing.

Hip rafters may need to get bigger as well. I would use something like this:

Some will say this is not your job. To them, I say "good luck with that attitude". In a big city or a well-trained city, you can get away with that. Small town, without powerful friends, not so much.

 

[bill1952]

Google says that area of TN has a population of a little over 6,000 people. To get along in an area like this, you are going to have to become good at figuring out how to fix stuff like this without an engineer, and being able to show people that the math doesn't math on these spans. You will need resources outside of the code, and you will need to know how to use them, and you will have to be able to articulate how you reach the conclusions you reach. You are going to need to be resourceful. A beam software like BC Calc is your friend. You can't just say it is wrong, you have to be able to say what it takes to make it right as an option to getting an engineer.

My opinion is that this could be made to work (mostly) prescriptively if rafter ties are installed perpendicular to the ceiling joists to keep the walls from spreading, collar ties are installed in both directions, and the ceiling joists spans are broken with LVL beams to span IRC. Garage headers to be sized IRC or LVL as the span may dictate. The lumberyard is your friend, or you can use BC Calc if you know what you are doing.

Hip rafters may need to get bigger as well. I would use something like this:

Hip roofs don't require rafter ties. Research it. A combination of the load on hips at the corners tied together by the top plates with the sheathing providing a diaphragm. But don't believe me, Google it.

 

[icebox14]

The fact that it is built for the pastor should not be a factor unless it is on the same property as the church. I understand churches expect leeway, but if it’s on the lot with the house and that is remote from the church, it’s a separate parcel and could be sold to the public.

I agree 100% but that is not the reality of the situation in which I work. I cannot begin to count the amount of churches that are congregating out of old doctor offices, restaurants, shops, etc. My particular favorite is a church of about 30 people that rent their space from the daughter of a dead "doctor." They requested an advice call to tell them what they needed to do in order to get a CO. Half of the space was a thrown together chapel, the other half (where they held Sunday school) was the patient rooms with medical supplies still on the counters. The fridge was packed with stuff for allergy shots, botox...who knows. I was with the Fire Marshal and Senior Building Inspector. They ended up telling them that they needed to get an engineer designed plan to do whatever it was that they wanted to do. Pastor said he could not afford that. When we walked out the guys I was with both agreed they would never hear from them again. As far as I know we didn't, signs for Jesus, botox, and allergies are all still posted right next to each other on the building. Packed every Sunday.

Also, the garage is attached to the carport of the house with a little breezeway so they could get by with having an accessory structure in their front yard. Church is like 2 or 3 roads down from the residence.

 

[icebox14]

Google says that area of TN has a population of a little over 6,000 people. To get along in an area like this, you are going to have to become good at figuring out how to fix stuff like this without an engineer, and being able to show people that the math doesn't math on these spans. You will need resources outside of the code, and you will need to know how to use them, and you will have to be able to articulate how you reach the conclusions you reach. You are going to need to be resourceful. A beam software like BC Calc is your friend. You can't just say it is wrong, you have to be able to say what it takes to make it right as an option to getting an engineer.

My opinion is that this could be made to work (mostly) prescriptively if rafter ties are installed perpendicular to the ceiling joists to keep the walls from spreading, collar ties are installed in both directions, and the ceiling joists spans are broken with LVL beams to span IRC. Garage headers to be sized IRC or LVL as the span may dictate. The lumberyard is your friend, or you can use BC Calc if you know what you are doing.

Hip rafters may need to get bigger as well. I would use something like this:

The municipality I work for is about 50k, I live in a town in a different county. Where I live the state does inspections, but I have never seen or heard of anyone inspect anything. My county does not have zoning restrictions or code enforcement, it's great.

I spend way too much time in my off time researching and trying to figure things out. I want to be able to explain the why for any given situation and I am in a masters program at LSU attempting to do that, but I cannot in this situation. I can point out what I know is wrong but I also know there are things I am more than likely missing since I have never inspected anything close to this. I cannot find anything in the 2018 IRC or IBC that will help me in this situation. I am not qualified and I will never be qualified to give someone advice on how to make something this unconventional structurally sound. I am not going to be held liable for giving my opinion and it failing.

I spoke with my CBO this morning, he was shown more photos than what I posted on here but he agrees this is out of our scope and the GC was told this morning to get an engineer to look at this. No one in my dept is in agreement with how the loads are being distributed and that is enough right there to let me know this is way over our heads. Just wanting to learn from this one.

 

[SDS]

Google says that area of TN has a population of a little over 6,000 people.

Dang! I'm moving to Tennessee! How's the deer hunting there?

 

[redeyedfly]

No snow? This looks fine. Are you worried it's going to collapse? From what load?

Send it

 

[icebox14]

Dang! I'm moving to Tennessee! How's the deer hunting there?

At times there are 7-10 deer in the field across from my house. But typically it’s 2-3 on a daily basis. I have a Great Pyrenees and a mastiff- the deer come up not phased at all to get to the apple trees. A lady actually stopped by one evening to tell me that my Pyr was playing with a doe when she drove by and she just had to tell me how cute it was. I had no idea who she was.

All that to say, I am not a hunter but my friends that do hunt have no complaints. There is always an abundance of deer jerky at the office.

 

[icebox14]

No snow? This looks fine. Are you worried it's going to collapse? From what load?

Send it

I guess I’m concerned because I have never seen anything like it. 2x6 joists spanning 24 feet concern me. They have 5 and 6 inch anchor bolts on a double sill plate. The header above the garage is too small. I thought if a requirement is in the code it’s in there for a reason. But please enlighten me so I can learn from this.

And we definitely get snow. I can’t tell you how many trees I have lost just because of snow. We got 16 inches within just a few hours a couple years ago. Granted that’s not typical but we get 2-3 good snow falls a year. It’s not like how it used to be when I could wear a t shirt while riding my horse on Christmas. Our area was devastated last year from hurricane Helene.

 

[Yankee Chronicler]

Hip roofs don't require rafter ties. Research it. A combination of the load on hips at the corners tied together by the top plates with the sheathing providing a diaphragm. But don't believe me, Google it.

This struck me as counter-intuitive, so I did an internet search. What I found is terrifying. Most of the articles I found use the the term "hip roof" to refer to a standard gable roof, and most of them didn't understand the difference between a collar tie and a rafter tie. Your explanation about a "diaphragm" also doesn't make sense to me.

Do you have a link to an article that explains how this works in correct terminology?

 

[bill1952]

Teaching is not my strong point. I apologize but left out the fact that the hip rafters are acting like a ridge beam. The pryamid of the 4 hip rafters if the bottoms are anchored can't spread or collapse (assuming they were design for the loads. The top plates - in tension - just won't let them "spread". So that apex can't can't sink like a gable roof and ridge board.

Here's one from FHB: https://www.finehomebuilding.com/forum/collar-ties-on-hip-roof

Another from Eng-Tips, a site I find refreshing for it's objectivity: https://www.eng-tips.com/threads/rafter-ties-on-hip-roof.354174/

If it's a hip roof but has a ridge between hips, it only can work if the short ridge will function as a ridge beam. A 1x8 might for several feet. I lived in a 1904 built house for 30 years in Chicago burb with a big attic. Many in the area finished them - ballrooms. House was 30 x 36. No rafter ties. I pulled strings and used a laser level - not an 1/8 of an inch of sag. The top plate was about 18" above the 2nd floor ceiling joists, hips were 2x6, commons and jacks were 2x4. So I know it's very possible. Pryamids are very structurally sound.