Roof Beam replacement.

[EddieWalker]

I agree with the others about the truss not being built properly. I also agree that there needs to be something connecting both walls together that will stop them from spreading apart.

If it was mine, I would move that wall so it's under the failed truss and make it a load bearing wall to support the roof.

Removing any parts of that truss can lead to other issues that I wouldn't want to deal with. Scabbing on new lumber to the broken lumber would make it better, but not solve the problem.

Then I would build brand new trusses on either side of the existing trusses. There are charts for how to design a truss for how far you are spanning. I would do this for every truss in the building. And if I got really crazy, I might add a truss between every existing truss just so I wouldn't have to ever deal with it again.

 

[BlueKnife]

Then I would build brand new trusses on either side of the existing trusses. There are charts for how to design a truss for how far you are spanning. I would do this for every truss in the building.

And get rid of the offending braces on the old trusses.

 

[Chewwy]

More than likely they're 10 ft. apart. That's the standard in the area where the OP and myself live.
. . .

Ten feet apart might be ok for properly designed, constructed, and supported trusses. The one in this post does not meet that criteria.

 

[RobertEH]

Thanks for all the replies - I plan to go over to the neighbors tomorrow and get some more data based on the replies here.

I do like the idea of sistering up the broken board rather than replacing it.

I am not a roofer so some of the terms and physics here are beyond my knowledge. Can someone explain in layman's terms what it means that the horizontal beam is "in tension"? Does that mean the horizontal beam is being pulled horizontally towards the walls (preventing wall bulge) rather than being pushed down by the weight of the roof?

 

[EddieWalker]

A truss is a bridge that spans from wall to wall. If you just put up two rafters to create the roof, the weight of the roof will push out the walls. You need to connect the walls together so they do not spread apart.

The truss is then designed based on how far apart the walls are, how much weight you need to support and how close together each truss is. I personally like to put my trusses every four feet so I can use 2x4's on the flat for purlins.

 

[BlueKnife]

Ten feet apart might be ok for properly designed, constructed, and supported trusses. The one in this post does not meet that criteria.

Correct. Those trusses need to be completely redesigned or replaced.

 

[BlueKnife]

I am not a roofer so some of the terms and physics here are beyond my knowledge. Can someone explain in layman's terms what it means that the horizontal beam is "in tension"? Does that mean the horizontal beam is being pulled horizontally towards the walls (preventing wall bulge) rather than being pushed down by the weight of the roof?

"In tension" means it's being pulled on. "In compression" means it's being pushed on. The bottom cord is supposed to be under tension. Because of the incorrect design of that truss, the bottom cord is receiving significant downward force where those diagonal braces attach to it, which is why it broke. There should be no downward force on the bottom cord, other than what it's getting from it's own weight and whatever is hanging from it, like a finished ceiling. Sistering another board to it is just kicking the can down the road, not solving the problem. If your neighbor insists on doing that, he should, at the very least, get rid of those diagonal braces. They're causing most of the problem.

 

[MAX-24-Dean]

A visual description of compression and tension in a beam, attached. Complements of Tauton Press.

 

[MH8675309]

A truss is a bridge that spans from wall to wall. If you just put up two rafters to create the roof, the weight of the roof will push out the walls. You need to connect the walls together so they do not spread apart.

The truss is then designed based on how far apart the walls are, how much weight you need to support and how close together each truss is. I personally like to put my trusses every four feet so I can use 2x4's on the flat for purlins.

Every four feet is a good rule but the purlins in this building are set on edge and appear to be 2x6s so that you can space the trusses farther apart. Ive seen it both ways and both are tried and tested - boils down to preference I spose. The trusses on the other hand look like they used way more lumber than needed. A properly designed truss would take way less lumber and hold up better. We built our own years ago using plywood for gussets - but to an engineered plan - and they're still holding up fine

 

[ning]

Every four feet is a good rule but the purlins in this building are set on edge and appear to be 2x6s so that you can space the trusses farther apart. Ive seen it both ways and both are tried and tested - boils down to preference I spose. The trusses on the other hand look like they used way more lumber than needed. A properly designed truss would take way less lumber and hold up better. We built our own years ago using plywood for gussets - but to an engineered plan - and they're still holding up fine

I'm not surprised to see trusses only at the vertical posts, particularly since the trusses are doubled there.
But, 2x6 seems small for a 10' span between them to me, especially with a 24" center.

(nb I suspect this barn is 24' wide, not that this makes a difference to the truss question)