# Truss Load Capacity



## kramttocs (May 26, 2014)

I've been looking around online for similar topics and found this one: http://lumberjocks.com/topics/43029 where everyone seemed to know what they were talking about 
Had a situation where I needed to lift a piece of equipment to load on a trailer and thought having an overhead winch would be useful. 
Was wondering if spanning a pipe over several of the rafters would be able to handle any significant load (like 500-600lbs)?
My barn is 40×60 with the rafters on 24" centers. If it is possible, I would put the pipe about 5 feet from the wall.
I've attached some images but will gladly provide any additional information that might help. Based on what I have been reading, I suspect the answer will be that it would be a bad idea.


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## CudaDude (Jan 30, 2012)

Well I'm certainly no engineer, but I don't think it matters how many rafters you span the pipe across. The rafters on each side of the load are going to bear all the weight. I think it's a bad idea. Try checking with your local auto parts house. Ones around here used to rent out engine hoists for just a deposit and then you get that back when the tool is turned back in.


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## kramttocs (May 26, 2014)

Thanks Gary! The two rafters bearing it all makes sense and one nay is enough for me to not risk my roof.


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## firefighterontheside (Apr 26, 2013)

I guess you've already decided not to do it, but I think you could do it and be fine. I've seen some pretty big carpenters during construction standing on one bottom cord and not causing the thing to fall. You could use something like a 6×6 and actually distribute the load to several trusses. I'm no engineer and you will probably not find something to tell you how much weight the bottom cord will support, because it was not designed for that. Do what you feel comfortable with though.


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## REO (Sep 20, 2012)

if the roof is high enough put a spanner between two on one end and two on the other end in the crotch where the members meet. then hang the pipe between the two from the center of the spanners. make sure you pick up the load between the centers of the middle two this will exactly distribute the load between four trusses. that would be less than 150 pounds per truss. as has been said most contractors weigh more than that. the problem with throwing the beam or pipe between the top and bottom chord is that under load the beam flexes and does not deliver a distributed load across the span.


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## kramttocs (May 26, 2014)

Thanks guys. After the votes of confidence, I am back to entertaining the idea of doing this. The spanner approach makes sense and getting it down to 150 per truss isn't worriesom.
With the same idea (the roof is 11' high to bottom of truss) since I am not wanting to life anything that high, would another layer cut it down more? So to use REO's example:

(Assume everything is equally spaced)










Is it correct that this would be down to 100/truss given 600lbs?


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## kyscroller (Mar 20, 2013)

Most trusses that support metal roofs are designed for a 20lb live load and at most 10lb ceiling load per sq ft. I design trusses everyday. I wouldn't do what you're thing of doing. The trusses are not designed for the exter load even if you distribute it over a few of them. May want to think about making a tripod setup or making a setup like a swing set but supporting the legs so they won't spread when the load is lifted. Bolt everything together and don't use screws. They are too brittle.


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## thetinman (Mar 10, 2014)

It appears from your pics that you have scissors trusses on the wall and out some distance where they transform into center span trusses. If this is the case I don't see any reason the scissors can't carry a total load of 500 lbs spread out across 3-4 trusses as others have described. I personally think even more weight could be lifted. The scissors are at an angle. That's important because it means that the wall itself is carrying part of the load. I'm not going to get all nerdy here so to keep it simple - if the angle was 45 (I know it's not) ½ the weight would be on the truss members and the other half directed to the wall. Your angle is steeper so more weight is angled to the wall and less "sag" weight is on the truss.

I've lifted the back end (engine end) of a 2400 lb golf course greens mower by spanning only 2 horizontal trusses and let it hang for 1 ½-weeks waiting for parts. Call that a 1200 lb lift. Frankly I was nervous about it but had no other options. Worked fine. I wouldn't hesitate to do what you are talking about - simply lifting loads from time to time. That's just me and I offer it for what it's worth.

Heck, you'r get more weight than that if you drywalled the ceiling.


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## REO (Sep 20, 2012)

HEY! how did you get that to work? I tried the same EXACT approach to a diagram and it came out all scrambled!
The truss loads are per square foot. take the span times 30 (sum of live and ceiling load) and you get the load that the truss is designed to carry bearing on one end since the trusses are 24" OC. point loads are not so neat and tidy but you have plenty of cushion In my opinion.


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## kramttocs (May 26, 2014)

You get all the credit for that diagram for sure  
Yours came through the email and I assumed you edited it out of the post but wasn't sure why….until I tried to do it myself and quickly understood.
So I took a screenshot, threw it in ms paint, and inserted the image.

I really appreciate everyone's input on this question. While I lean towards it being able to handle it without issue, there's always that 'what if' factor. My dad's a good welder so building a sturdy and portable swing set setup seems to safest route.


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## JollyGreen67 (Nov 1, 2010)

Firefighterontheside has the right answer. There are several different truss designs - some distribute loads to the outside walls, some designed to hold weight, i.e., attics. The ones you have pictured are outside load bearing trusses, not for hanging items from them.


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## AlaskaGuy (Jan 29, 2012)

I did a Google search. I found this said several times. "Trusses are typically designed for about 10PSF on the bottom chord. That's to allow for drywall, insulation, and misc. loads".

Is it worth the chance?


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## kramttocs (May 26, 2014)

Nope  
After looking at gantry cranes they fit the bill perfectly and offer a lot more flexibility.

I've learned a lot from this thread. Thanks all!


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## woodchuckerNJ (Dec 4, 2013)

You don't state where you live.
If you live in a northern climate, you already have experienced snow loads.
More than 500lbs.

Just some info.


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## bigblockyeti (Sep 9, 2013)

You should be fine depending on where in the country your pole barn is. If it's where snow is possibility and whom ever designed it to meet code, the trusses by default have to support a much greater load than they are normally loaded to with nothing on the roof. Whatever you place against the bottom of the trusses, it would be a good idea to attach it by means of all thread or something similar running to close to the very top of the truss, effectively loading the top instead of just pulling on the bottom. I have seen this done many times with a lightweight tall section I-beam supporting a beam trolley to move heavy things along a single plane in a building. One other consideration is having the pipe or beam substantial enough to distribute the single point load to all of the trusses and not with the vast majority being placed on the truss closest to that load.


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## PLK (Feb 11, 2014)

Kiss!
Keep it simple stupid!

Not directed at anyone, have you considered a 1 ton shop crane? HF sells one cheap.sounds like it should fit the bill at under $200.

Paul


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## shawnmasterson (Jan 24, 2013)

To those talking about snow load, that in no way applies here. It you were lifting from the top chord then it would matter. Picking from the bottom chord is a bad Idea. The bottom chord has very little strength added from the truss as a whole. If I were considering something like this I would contact a truss manufacturer and fisk there for advice.


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## bigblockyeti (Sep 9, 2013)

The top chord is exactly what I was referring to when stating the beam/pipe needs to be attached very close to the top of the truss. The primary load on the bottom chords is tension and designed for little else.


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## PLK (Feb 11, 2014)

While you him and haw about truss load capacity, OP get yourself a simple rolling floor shop crane to load the trailer. HF has one under $200 and it will load your trailer without having to rig anything up. Which would cost your quite a bit more.

Paul


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## kramttocs (May 26, 2014)

Oh, as a couple of my posts above state, I've decided to go the gantry crane or (since you brought it up ) cherry picker route. The latter having the price and storage options in its favor. 
But there's some good info/opinions in this thread that I hope will help others if considering the truss route.


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## PLK (Feb 11, 2014)

Welcome to LJ's

Paul


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## MrRon (Jul 9, 2009)

This is how I would reinforce the trusses.


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## Ocelot (Mar 6, 2011)

When I bought my planer, I found one of those 2000lb "shop cranes" (HF) on CL for $50 and used it to unload the planer from my pickup. It would work much better with a trailer. I had to let air out of my tires to get the truck to sink a bit.


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