Truss orientation

[Pauljt]

I know that it's an odd (and maybe dumb) question but here goes. In a 20x30 shop I know that traditionally the trusses would span the width (20ft). Could they go lengthways (30ft)? I started thinking it over and can't seem to get my head around it.

 

[dfiler2]

Sure, the building would just be wider than it is long. A 32 ft truss would be very common.

 

[The Cobbler]

sure. any orientation is fine. go with what looks best for you

 

[Mick56]

Which side will your doors be on? You don't want snow dripping and sliding off in front of your doors all winter.

 

[Innovate1]

For that size building it isn't a big deal which way they go. If the building was significantly longer in one direction than the other the trusses would be smaller and have less load on each one (and allow smaller headers) if run across the shorter direction. Mick56 makes a good point about snow dripping off over the doors. Also, if the roof slopes that way the ends of the trusses are supported by the headers over the OHD. That can require a sizable header, especially for a double wide door. I would run the trusses parallel to the wall that has the OHD if possible although you may have other reasons that outweigh those considerations.

 

[aventino68]

From where I am 36-38 starts getting max distance for my trusses, do you want support columns?

 

[Pauljt]

The ohd could go in the side of the shop rather than the front (which would now be the side. I'd turn the building 90 degrees). I'm still figuring out the building layout. Came across a guy close by with 12 engineered trusses. He said they measure 30ft 11in. from heel to heel with 16in overhang. They are new. $800.

 

[The Cobbler]

make sure you get the engineers/specs papers with them, or they are virtually useless

 

[Pauljt]

make sure you get the engineers/specs papers with them, or they are virtually useless

Yup. He has them.

 

[Pauljt]

Still trying to get this straight in my head. So if I used post frame construction with ten foot spacing between the posts, the three posts on each end would be load bearing. Any posts going on the 30ft sides would be mainly for rigidity for the walls? And to build inside walls off?

 

[firebirdparts]

Sort of. It's not too usual to set an engineered truss on top of the end wall. Often, the wall is load bearing and holds up the end of the roof and the overhang. Now, that's not too heavy, and the end wall is 10X stronger than necessary, but it is technically holding up that little bit of load. Normally.

But you're right, rigidity of the end wall is the main design issue there.

 

[Pluribus]

Were they engineered for a stick built building, or are they made for a post frame building to support purlins vs. sheathing? The quantity of them makes me wonder, as that would make for a long, skinny building if you used all of them.

 

[aventino68]

http://www.cascade-mfg-co.com/files/media/rooftrussspanchart.pdf

Not sure what you require snow loads wise, I'm also Ontario but further north than you and I'm flat roof with at least 42 ft span

 

[spudley]

You can go either way but take a look around and you'll see far more rectangular structures using the short side as the gable wall.

LVL's carry plenty load for wide doors. If you're worried about snow, increase the overhang to two feet.

 

[ddurrett896]

Mine are 28'

 

[CraigStu]

Are all those trusses load bearing? See the drawing on page 8 here;
http://www.cascade-mfg-co.com/media/a-builders-guide-to-trusses.pdf
Notice the end truss is a different design because it has a wall under it. I am not sure that style truss would work if you want a door in that wall. I may be wrong here so hopefully others will chime in.

 

[Innovate1]

They can certainly go either way. I recently had trusses designed for a 50 ft span for a long narrow building because of the lot size and desired look. And they still were made from 2x4 members. But the end loading and support must be beefed up for longer trusses. Not sure at what point the end support area would need to be increased to prevent crushing the wood.

LVLs can be sized for large doors either way. I was just pointing out that less support (cheaper) can be used if the large doors are in the gable end even if the load of that one truss has to be supported by the wall.

The trusses are designed for a given spacing. For most conventional construction it is 24". Trusses for post frame buildings are much heavier. Sounds like the trusses you are considering are not for post frame. You need to get that straight of you will have big trouble. The length is also about a foot wider than the building. That could be a problem too as the support is normally where the upper and lower cord come together. I would want to at least run that by the truss designer - they may ok it or be able to define reinforcement to make it acceptable.

 

[dfiler2]

Still trying to get this straight in my head. So if I used post frame construction with ten foot spacing between the posts, the three posts on each end would be load bearing. Any posts going on the 30ft sides would be mainly for rigidity for the walls? And to build inside walls off?

Keep in mind that the extra material and cost to add 10' to that building would be minimal.