reason for not spanning wood truss over 40'

[Shovelhead]

The folks I'm working with to get quotes on a shop are telling me they prefer not to span over 40' with wood trusses on a stick built building.

I remember reading somewhere that the cost may jump substantially once you go over 40'.
Is that correct?
Is there any other reason why?

Shop would be 48-50' in length.

~44w x 48d

Thanks

 

[Dagny]

Should be easy in texas you dont get much snow. Here roofs are designed for 30 lbs per square foot and once in a while if we get 3 feet of snow they cave in.

I'm building right now and I told them I want 60 lbs. adds about 1000 dollars to 36x40 shop.

Too old to shovel off roofs.

 

[firebirdparts]

The forces in a truss are only tension and compression. As the building gets wider the tension in the bottom chord is going up, so there are some break points where they might say they don't have experience making a suitable joint for that. It's not "hard to do" exactly, but it's also not hard to keep the factory busy making trusses of ordinary size, I guess.

 

[brewchief]

There is a point where the height of the truss makes it difficult to transport, you end up with a two piece truss, the top is a separate piece. I dunno if 40 foot is that point as it depends on the roof pitch. Trusses over a certain size may be more then the equipment that the company you are talking to can handle and they would have to bring in a boom truck or crane to set them.

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[Shovelhead]

Just got an email back from them and they stated:

"It’s just specifically to do with wood being strong enough to span.

If you need 44’ we can do it. It’s no problem"

Have not discussed roof pitch which was my mistake and I'm sure a critical part of this construction.

but I replied back and asked if "we can do it no problem" meant......
you can do it with a weakened system built 44' same as the 40' ?
or, you can do it with a beefier truss built different than the 40' truss.

4/12 or 5/12 roof, 48' deep, 12' eave

 

[Bretny]

Could it be for the shipping aspect? Not sure what the length of a normal lumber delivery truck is.

 

[Leaflessshadetree]

What I would imagine they mean that they can do 44'. If you are willing to pay for it.
The trusses will be more expensive and you may need more of them. Laybor and transport costs will also probably be higher.
There is a point where steel becomes more efficient.

 

[zmotorsports]

Mine was engineered for the snowpack we get here in Northern Utah and mine span 50'. Granted they are 2x6 construction rather than 2x4 construction and a 5/12 pitch.

 

[Shovelhead]

They're tellin me they would build a stronger truss. Well no chit, I'd hope so.
Cost difference would be $3500-$4000 !
According to my arithmetic, 12 trusses, on 4' centers would be about 300 bucks more per truss. Holy ****, does that sound right?

I asked them if they were designed to have bulldozer races on the roof.

 

[Kaizen]

Just got an email back from them and they stated:

"It’s just specifically to do with wood being strong enough to span.

If you need 44’ we can do it. It’s no problem"

Have not discussed roof pitch which was my mistake and I'm sure a critical part of this construction.

but I replied back and asked if "we can do it no problem" meant......
you can do it with a weakened system built 44' same as the 40' ?
or, you can do it with a beefier truss built different than the 40' truss.

4/12 or 5/12 roof, 48' deep, 12' eave

The truss company will build as needed. A longer truss is engineered to be just as strong.
Guessing your builder is saying this. As said depending on pitch it will be in multiple pieces and require additional labor and possibly a bigger machine/more framers to install.


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[Shovelhead]

Mine was engineered for the snowpack we get here in Northern Utah and mine span 50'. Granted they are 2x6 construction rather than 2x4 construction and a 5/12 pitch.

Z, I was hoping you'd reply.
Do you remember the cost of them 50 footers?

 

[Shovelhead]

The truss company will build as needed. A longer truss is engineered to be just as strong.
Guessing your builder is saying this. As said depending on pitch it will be in multiple pieces and require additional labor and possibly a bigger machine/more framers to install.


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Reckon they all ship on a 40' flatbed?
4 more feet and a red shop rag will git er done. LOL

 

[zmotorsports]

Z, I was hoping you'd reply.
Do you remember the cost of them 50 footers?

I'm sorry, I don't have that information. All construction costs were encompassed in the quote from my contractor and not broken out in an itemized format.

 

[Shovelhead]

a misunderstanding.
The 3500-4000 cost difference was not just for trusses, it was over the total cost of the building.
4' longer, beefier trusses, additional roof sheeting, trim, etc....

So maybe that could be right.

Thanks for all y'alls replies.
Keep em comin.

 

[Bert_]

60' isn't uncommon with wood trusses

 

[sberry]

I set a bunch of 80. Set them 2 at a time with different length chokers. We had a 72 ft clear. Yes the trust cost more, it's also coverin a larger area. I see a lot of these small buildings, 30x40, should be 40x30 so doors can go in the gable, yes they cost more but need less.
16 longer ones or 21 short.

 

[matt_i]

Of some concern is the width. On a 40ft span truss there's 20ft per side. On a 5:12 its 100" of center height. Max transport width is 102". As said it can be handled with piggyback trusses but its extra work for the framers.

 

[Kaizen]

Reckon they all ship on a 40' flatbed?
4 more feet and a red shop rag will git er done. LOL

My 32’ ones were the smallest on the trailer when they came. Some use a tandem trailer for long ones. No problemo. You’re paying get it how you want if at all possible. Have fun


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[nadogail]

I got lost looking for the pitch of the 40+ foot truss. IMHO there was not enough information given to offer a solution to the problem.

I recall seeing long trusses in Bus Depots where the buses pulled in, it's been a lot of years but there was room for 6 buses to load passengers at a time.

Welded Bar Joist trusses were used to support a flat roof with an Alaskan snow load on it.

 

[farmall400]

My trusses are 48'. They came in one piece on the trailer. The trusses were loaded upside down on the trailer and the peaks poked through the deck and were about a foot off the ground. The tractor had a boom crane behind the cab that they used to unload and set with. It was a pretty interesting set up

 

[Shovelhead]

My trusses are 48'. They came in one piece on the trailer. The trusses were loaded upside down on the trailer and the peaks poked through the deck and were about a foot off the ground. The tractor had a boom crane behind the cab that they used to unload and set with. It was a pretty interesting set up

There ya go, all about the "riggin".
Sounds like that was a pretty interesting operation.

 

[Bretny]

Of some concern is the width. On a 40ft span truss there's 20ft per side. On a 5:12 its 100" of center height. Max transport width is 102". As said it can be handled with piggyback trusses but its extra work for the framers.

Very true. I forgot about the max road width.

 

[karoc]

Call these people and ask your questions https://www.alliedtruss.com/ they will email a quote with drawings and all the specs.
If still can't get what is needed for your project,maybe can add beam be it steel or laminated

 

[41plym]

4' centers isn't 2' centers standard for wood trusses?

 

[Firebrick43]

The big cost jump is due to the increase in size of members to meet the strength. Truss manufactures need very specific quality wood which is common and somewhat easy to get in 2x4 and 2x6 but is uncommon and expensive in 2x8 and larger. There is even a big jump in 2x6 over 2x4. I wanted 2x6 bottom chord trusses and the extra cost made me cringe so I stuck with 2x4

4' centers isn't 2' centers standard for wood trusses?

Not with pole buildings. 4’ trusses with 8’ of poles is very common. 5’ trusses with 10’ poles is common around here to. Older pole buildings here uses heavier trusses on 8’ spacing, purlins on edge instead of face. I have not seen a building under 25 years old however doing 8’ centers

 

[Bert_]

Around here even stick built is usually built with rafters on 4' centers if it's getting a steel roof.

Lots of pole buildings with wood rafters on 8' centers. 60' wide too.

 

[firebirdparts]

Just got an email back from them and they stated:

"It’s just specifically to do with wood being strong enough to span.

If you need 44’ we can do it. It’s no problem"

Have not discussed roof pitch which was my mistake and I'm sure a critical part of this construction.

but I replied back and asked if "we can do it no problem" meant......
you can do it with a weakened system built 44' same as the 40' ?
or, you can do it with a beefier truss built different than the 40' truss.

4/12 or 5/12 roof, 48' deep, 12' eave

The higher the roof pitch, the easier it is to make it strong, but of course the weight carried on the roof is more. I would think they don't mean a "weakened" option.

 

[sberry]

Around here even stick built is usually built with rafters on 4' centers if it's getting a steel roof.

Lots of pole buildings with wood rafters on 8' centers. 60' wide too.

here would be 2 ft oc.

 

[sberry]

Actually most is in this area

 

[sberry]

Around here even stick built is usually built with rafters on 4' centers if it's getting a steel roof.

Lots of pole buildings with wood rafters on 8' centers. 60' wide too.

here would be 2 ft oc.

 

[tarmy]

There is a point where the height of the truss makes it difficult to transport, you end up with a two piece truss, the top is a separate piece. I dunno if 40 foot is that point as it depends on the roof pitch. Trusses over a certain size may be more then the equipment that the company you are talking to can handle and they would have to bring in a boom truck or crane to set them.

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It is this...more complex to build in two pieces per truss...more complex to assemble and cost go up steeply.

My trusses, in snow country, are 38’ and are two pieces. Mine also have living space in them...with a 200lbs PSF floor load calc in earthquake country. They were expensive. The roof sheathing gets complicated too.

 

[sberry]

I set about a 500 80 ft, one piece.

 

[joe_padavano]

Why is this even a question? Indoor riding arenas use wood trusses up to 90ft wide.

 

[reader2580]

I set about a 500 80 ft, one piece.

It all depends on the roof pitch. An 80 foot 4/12 pitch common truss would be just over 13 feet high. I don't know if that is too wide for an oversize load. 3/12 or 2/12 should be fine as one piece.

My brother's house under construction has 12/12 trusses. They came in two pieces.

 

[DJF3]

I have 34ft attic trusses. Small compared to what you guys are talking about. 2x8 MSR bottom chord. They were set 6 years ago at 24" spacing on a post and beam structure. 7/12 pitch with a tin roof. I've taken them down to build a bigger shop, and the building code has changed. I now have to set them at 19.2" centers. I couldn't even fathom 4' centers! Makes me nervous just thinking about it.

 

[Homerr]

Many good reasons have already been mentioned. I'd speculate that the gang plates used to hold the trusses together may be a limiting factor. They may need to use larger plates than 2x4 or 2x6 can handle. If the plate is 7" wide they may need to build the truss, or parts of it, out of 2x8 and this could drive the costs up. And their truss building tables may be set up for a 'standard' of 2x4/2x6 lumber and they may need to reset things.

Another reason for the cost difference is that it could be the 40' truss is already in their system as a designed item. Maybe they don't already have a 44' truss and need to design/engineer this length.

Here's a video that shows an older truss table system:

And here's the newer automated pin type:

 

[Jeffh40]

Not that it cannot be done with the wood , but just there is a point where building with steel joists is more economical than wood trusses.

Www.newmill.com

 

[rayra]

They're tellin me they would build a stronger truss. Well no chit, I'd hope so.
Cost difference would be $3500-$4000 !
According to my arithmetic, 12 trusses, on 4' centers would be about 300 bucks more per truss. Holy ****, does that sound right?

I asked them if they were designed to have bulldozer races on the roof.

You're starting to sound like the kind of customer that should be fired.
Could you make it more tedious and contentious? You seem to not be communicating effectively with them. It isn't a damned hot potato / tennis match, it's an RFQ.
Just tell them exactly what you want / need and get their answer / cost.

 

[Wrench97]

Reckon they all ship on a 40' flatbed?
4 more feet and a red shop rag will git er done. LOL

Flatbeds are 48' and 53' today.

 

[iagsxr]

There are reasons buildings end up being common sizes. Unless you have a really good reason when I see you want a 44' x 50' whatever, what you really mean is you want a 40' x 60'.

Back in my previous life as a crane operator, 60' & 66' trusses were like everday. 72' wasn't uncommon. 4/12 pole barn trusses. Shipping shouldn't be an issue unless you're somewhere they physically can't get a truck to.