Attic truss limitation question.

[rerod]

My vision came from my old barn with a 8/12 roof that I'd like to replace with a new energy efficient barn. But it doesn't look like attic truss's in a barn shape can be built, requiring to switch to 12" rafters. But rafters are difficult to vent and insulate to today's standards. I wont use foam, so the rafters would have to be open web parallel cord truss's to use cellulose.
I understand that attic truss limitations are based on structural stability and what can be shipped on a flat bed semi, so can someone in the industry tell me how long and tall of a truss a semi can carry? I left out the attic walls in the scale drawing below, but I'm guessing the 12' peak might be to tall to ship? And is adding raised heel's to a attic truss possible? Second picture shows a silo down the hill from me to give you a idea what kind of winds I get, and why I didn't want a two story. But I might have to, and just forget my vision.

Thanks

 

[Hank11]

You’re gonna need to call the truss manufacturers in your area and see who can build and ship what. I suspect 40 foot won’t be a problem, but it’ll take some planning. For the 12 foot peak in the attic — they make piggyback trusses just for this reason. The piggyback is a small section that you fasten on top after you raise the trusses.

 

[rancherbill]

Easy peasy.

Forty feet is not a problem. The height is not a problem. They will a make a small triangle for the top. Thus your truss going down the road will be 8 or 9 feet and when they get onsite they just nail the triangle on top.

The roof on my house is 40+ span and 20 to the peak.

Here's a pic of a bottom to give you the general idea of what I am talking about. Just add the triangle. The truss company can adjust the webbing to give your storage space.

 

[TurnipTruck]

I got two different truss companies to bid on my shop build. One plant was four hours away and would require piggyback trusses; the other plant was a friend just down the road who restarted his operation to build these attic+common trusses without piggybacks due to the short distance away.




40’ span, 4/12 pitch, 7’ attic, 75lb LL, 4’ heel

 

[mike93lx]

I got two different truss companies to bid on my shop build. One plant was four hours away and would require piggyback trusses; the other plant was a friend just down the road who restarted his operation to build these attic+common trusses without piggybacks due to the short distance away.




40’ span, 4/12 pitch, 7’ attic, 75lb LL, 4’ heel

Being able to get those in a single piece is awesome. I appreciate that piggy backs are done all the time, but not having to deal with that is nice

 

[larry4406]

At the day job, the community I am currently doing the trusses are 44' long. They have piggy back top trusses. Piggy backs are used when the truss becomes too tall to truck down the highway.

The trusses sit flat on a special roll-off trailer. The truss bottom chord is typically on the driver's side and the "point" of the truss is on the passenger side. Depending on the amount of "wide load" you will typically see a transport assist vehicle as the truck goes down the highway to help control traffic.

My prior shop was 28' deep clear span with attic. Picture of first truss going up and it has a piggy back. The roof pitch was not symmetrical.


Shop has 3 dormers. Dormers created by girder trusses and in-fill framing. These dormers also generated floor space at the rear.





Miss that shop!

Link below has some nice details for gambrel attic trusses for a traditional looking barn. I would love to have one of these but don't see it happening unfortunately.

Gambrel Roof with Attic

Gambrel Roof with Attic

countryplans.com

 

[rerod]

Thanks folks.
I did contact midwest manufacturing in Marshalltown Iowa via email. They never told me about piggy back attic trusses.
The problem I see with piggy backs is there's not enough space for venting and insulation for zone 5. I think I'm going to ditch the barn vision and build two story, or forget the attic trusses and only use scissor to fit my car lift.

 

[Fav Onefour]

12 foot tall can be hauled with normal permitting. Length is definitely not limited to 40 footers. Highways are filled with 53 foot van trailers. Long load permitting allows up 65 feet on major roads without much hassle.

I would not limit you building options based on a grain bin down the road. I would guess that it was damaged during the storm in 2020. That storm took out a lot of perfectly well built structures. The bin in the picture doesn't even have wind rings.
It's hard to build for a major wind storm. I would build for high average winds. That stuff will rattle the tin off a poorly constructed building. Tall walls will huff and heave with a flopper build.

On site rafters shouldn't be a big deal with the right builder. As a kid I pounded nails in quite a few. We used to do all our barns that way.
I'm still trying to figure out the limitations on insulation with a truss system? Are you trying to do a conditioned attic space?

 

[beltfeed]

I had my building trusses quoted as attic trusses and standard trusses. My roof is a hip roof, so the amount of usable attic area was not cost effective for higher price attic trusses. With attic trusses the truss designer wanted them on 16" centers to carry an attic load, standard trusses would work fine on 24" centers. Mine where 6/12 pitch, raised heel, 14' tall and 50' long, shipped lying flat on a roller bed truss trailer.

 

[rerod]

12 foot tall can be hauled with normal permitting. Length is definitely not limited to 40 footers. Highways are filled with 53 foot van trailers. Long load permitting allows up 65 feet on major roads without much hassle.

I would not limit you building options based on a grain bin down the road. I would guess that it was damaged during the storm in 2020. That storm took out a lot of perfectly well built structures. The bin in the picture doesn't even have wind rings.
It's hard to build for a major wind storm. I would build for high average winds. That stuff will rattle the tin off a poorly constructed building. Tall walls will huff and heave with a flopper build.

On site rafters shouldn't be a big deal with the right builder. As a kid I pounded nails in quite a few. We used to do all our barns that way.
I'm still trying to figure out the limitations on insulation with a truss system? Are you trying to do a conditioned attic space?

Thanks.
That grain bin was damaged just recently, but 2020, I did lose parts of my roof. I had it repaired, but it was still leaking so when I reroofed it solo last fall, I had to go down to rafters.

Yes, I wanted the option to build the attic space into a conditioned space bc the home on the property is in bad shape. I've spent allot of time on greenbuilderadvisor, and sort of wish I hadn't bc builders don't like to be asked to do anything they haven't done. I think that's why Midwest manufacturing didn't want to help me with my insulation and venting requests.

I think I'll just build a regular single story bc the loft or two story were to get a better view from my property. Honestly, the view is what sold it.. Every time I step outside of my crummy house, I'm in awe of god's country. I had coyotes circling me last night.

 

[Skooterj]

I just built a 4 foot, 8/12 truss on Menards website with a 36 inch energy heel and a 20x8 attic space. $479 each..

 

[larry4406]

I just built a 4 foot, 8/12 truss on Menards website with a 36 inch energy heel and a 20x8 attic space. $479 each..

Circled region is where insulation gets pinched. We typically infill this region with a sloped member to get insulation depth and clearance for baffle vent.


Does the Menard’s site allow you to create that truss profile drawing?

 

[larry4406]

Only picture I have of the padded down region for insulation depth at attic pinch point.

 

[slim39]

My vision came from my old barn with a 8/12 roof that I'd like to replace with a new energy efficient barn. But it doesn't look like attic truss's in a barn shape can be built, requiring to switch to 12" rafters. But rafters are difficult to vent and insulate to today's standards. I wont use foam, so the rafters would have to be open web parallel cord truss's to use cellulose.
I understand that attic truss limitations are based on structural stability and what can be shipped on a flat bed semi, so can someone in the industry tell me how long and tall of a truss a semi can carry? I left out the attic walls in the scale drawing below, but I'm guessing the 12' peak might be to tall to ship? And is adding raised heel's to a attic truss possible? Second picture shows a silo down the hill from me to give you a idea what kind of winds I get, and why I didn't want a two story. But I might have to, and just forget my vision.

Thanks

 

[slim39]

Call Morton Buildings I sure they can haul them that size. Slim 39

 

[mike93lx]

Only picture I have of the padded down region for insulation depth at attic pinch point.

Do you have your truss supplier do that or is it done in the field?

 

[Hank11]

My shop with attic trusses worked out great with a bit of furring out to get almost 8" of open cell foam under the deck. It was easy and fast, I just wrote the check. It works well.

But nothiing says you have to insulate the deck. You can insulate over the ceiling (there is lots of room) and then the knee walls, letting the roof deck vent from soffits to ridge vent. Adding the braces like post 13 will cover that detail.

 

[Skooterj]

Circled region is where insulation gets pinched. We typically infill this region with a sloped member to get insulation depth and clearance for baffle vent.


Does the Menard’s site allow you to create that truss profile drawing?

I saw that. The 3d rendering had a bigger 'heel' there. I would talk with the truss designer over the chat function and see if they can either slope the room corner or raise the heel at the wall connection another foot. Or use exterior rigid foam over the sheathing. Or just build my own drop ceiling. I've always found them very accommodating when asked about specific designs. Especially if they have a base quote to start from.

 

[Skooterj]

Oh, and I know of one farmer locally that had 100 foot trusses shipped in 3 pieces for a clear span post frame. It wasn't cheap, and they had to plan the transport to avoid underpass and certain roads. Oversize load ******, etc. So a 40 foot span is nothing.

 

[larry4406]

Do you have your truss supplier do that or is it done in the field?

I saw that. The 3d rendering had a bigger 'heel' there. I would talk with the truss designer over the chat function and see if they can either slope the room corner or raise the heel at the wall connection another foot. Or use exterior rigid foam over the sheathing. Or just build my own drop ceiling. I've always found them very accommodating when asked about specific designs. Especially if they have a base quote to start from.

We field frame the clipped ceiling for insulation depth. Our truss vendor won't do that.

Also, with an attic truss, you typically will need to string line the uprights as they usually are not in a straight line and you will need to scab them so your vertical walls are straight. Then you add Thermo-ply or similar air barrier on the back side of the vertical walls to stop convective currents on the back side of the insulation. Sorry, no pictures of this. Extremely important to not omit this.

Lastly, you need to block the attic floor bays solid (so wind from soffit vents can't blow insulation thru yielding a cold floor). You also need solid blocking at the attic base board level. This picture shows how we blocked the attic truss bays solid and then applied spray foam to the bay blocking and the base board level blocking. Later after drywall, the dead attic space gets overblown to R43. Ignore the the sound bat rock wool the customer wanted. This detail is very important to getting a good seal at the attic.

 

[rerod]

Circled region is where insulation gets pinched. We typically infill this region with a sloped member to get insulation depth and clearance for baffle vent.


Does the Menard’s site allow you to create that truss profile drawing?

Exactly..
My good laptop is out for repair til monday, but the menards visualizer wouldn't allow me to add raised heels to the attic trusses, and the salespeople referred me the engineer who won't reply. My last email I sent was more or less.. "It seems like midwest truss doesn't want my business", with no reply. Apparently, they focus on easy designs and don't want customers with special requests.

My problem is I'm torn between repairing the small crappy home on the property which I already put a roof on, and then only needing a garage. Or removing the old home and starting from fresh. I've got OCD bad, so I'm back and forth about how much taxes would be vs keeping them low since I'm retired. If I built the shouse, it would be best to build it with three bedrooms for resale, after I've passed. But it's just me and a feral cat my X abandoned living here. I'm a hermit who is giving his son my three bedroom town house.
Below is a sketch when I was considering a shouse. But looks like my old laptop won't even upload that.

When I build, I'd like to follow guidelines from greenbuilderadviser called a "pretty good house" PrettyGoodHouse last book suggests whole-wall R value of 8 for slab, 15 for basement walls, 30 exposed floor, 25 for walls, 60 for attic. Thats 16" of cellulose and as mentioned, I won't consider foam.

But even a PGH might not be possible with local builders.

 

[larry4406]

Don’t give up on the attic truss.

As I tried to explain, the attic trusses require tuning to get them straight for finishes and insulation. Normal.

Framer will string line them for roof sheathing and soffit.

Then comeback and string line the uprights and clip the ceilings for the desired insulation depth.

You are fooling yourself if you are thinking you crane it into place and it’s done.

 

[rerod]

Don’t give up on the attic truss.

As I tried to explain, the attic trusses require tuning to get them straight for finishes and insulation. Normal.

Framer will string line them for roof sheathing and soffit.

Then comeback and string line the uprights and clip the ceilings for the desired insulation depth.

You are fooling yourself if you are thinking you crane it into place and it’s done.

But who am I to tell a builder how to build? I'm going to burn all my bridges out here trying to get the R-values of a PGH

 

[larry4406]

But who am I to tell a builder how to build? I'm going to burn all my bridges out here trying to get the R-values of a PGH

?

Truss vendor is an engineered component supplier. No different then the flunky that delivered the broken windows to you and asked if it’s ok.

The “builder” is you or your general contractor. The builder gives direction to the framer.

“Hey framer, clip this ceiling so I net X distance for insulation off the sheathing and string line these walls. Also add solid blocking at deck level and block the truss bays solid at attic walls”.

We get R43, Energy Star, and pass blower door tests. Not sure what you are trying to get to.

Good luck.

 

[rerod]

I was aiming for R60 ceiling, and ignoring challenges with cathedral ceilings. Attic trusses share the same issues, so I'm forgetting my second story view and I apologize for sounding a bit unhinged.