OT- truss rafter problem

Ray · May 7, 2012

We built a new home in 1976 and a few years ago we noticed the roof over the garage was bowed a little.It got a lot worse last year and we decided to get a new roof and find out what was going on.When they removed the ceiling in the garage the rafters were almost all pulled apart from the plates at the center of the garage.They said they had never seen anything like that before.When we tried to order new rafters we discovered the replacement rafters are 4 inches taller than the originals.The lumber guy at menards said a lot of houses built 30 years ago used different trusses.We had to go to a truss builder to get them custom made.Anyone ran across this before?

Bruce from Can. · May 7, 2012

Any truss I ever put up had a short chunk of what ever the bottom stringer was made from,[2x6 or2x8] on top of the butt joint.And a much larger stamp plate was used to hold it all together.

kevinj54 · May 7, 2012

Can you get a better pic? It looks like there may a member missing on those.

Adirondack case guy · May 7, 2012

It appears to me that the trusses were engineered to be spaced closer than installed for your location and snow load. Perhaps leftovers or something. Some one used genaric, or leftover trusses, and not ones engineered to code in in your area.

donjr · May 7, 2012

First time I've seen that. With that many cords pulled out, I think I'd want to check some walls. It almost looks like snow or something has caused the outside walls to bow out some or the trusses have shifted outward and caused the cords to pull apart. They look like they have about an inch of separation.

danofarming · May 7, 2012

You got a mess !! Can you jack and pull them back in place ?

Anonymous-0 · May 7, 2012

Have you ever had a down burst, (don't know if that's the right name or not). Opposite of a tornado with the pressure going downward. I've seen them do some strange thing's. Worked on a house where the pressure was so great that it buckled all the basement jack post. The guy said the tree branches were all pointed downward and touched the ground. Sounds like that might be a posssibility of what could have happened. No wall support under the garage part. Don't know, just a thought. Probably have to see the whole picture to tell for sure.

WJD · May 7, 2012

I'm not a structural engineer but if it was mine I'd get some come-alongs and slowly pull it back together. If you are able to pull it together reinforge it. I'd do something even if it will not pull together as if you don't my guess is the problem will get worse.

Ray · May 7, 2012

There 30ft trusses.The bracing you see under the rafters was put there by the contractor.He was afraid the roof would collapse with workers on top.He intended to sister the new trusses beside these.Going to tear the sheeting off tomorrow.

MarkB_MI · May 7, 2012

I'll bet one or both of the walls these trusses are resting on is no longer plumb. Either that, or the trusses weren't properly fastened to the walls.

1047pm · May 7, 2012

These trusses look to be made with 2x4 bottom cord and being 30 ft. span, set on 2 ft centers. I don't think they can carry the snow load. I don't know where you are located. Just my opinion.

EX 450 Owner · May 7, 2012

From the second picture it appears that the trusses that separated all set on a header or beam over the garage door openings. Has your contractor checked the header for sag or bowing?

dr sportster · May 7, 2012

They didn't just pull apart .Look at the way the metal connector pieces are bent out away from the wood. I'd say this garage has been shaking around a bit. If it was me [not a contractor --speaking as a layman] I would get out my best bed frame angle iron and drill holes . Then get all the used lag bolts in my collection. Then go up with come along or turn buckle and suck them back in.[After tieing across so they all pull back towards center at the same time -not individually] After that I would inspect everthing else. I don't know but new trusses would not be in the picture as much as fixing what happened then checking the walls for plumb and square. In other words fixing but not spending alot. Those two pieces want to be rejoined as soon as they can-- nothing else is broken or ruined as far as new wood . Just fix the failure. Right now they aren't supporting much. And what bent the plates away from the wood ?

david - or · May 7, 2012

I wonder if a car struck the center post between the garage doors sometime in the last 35 years. That could have put an inward or outward strain on the header supporting the trusses, which in turn could have resulted in separation at this joint in the truss.

Scott 730 · May 7, 2012

I don't see any lateral bracing on any of the truss members. The truss plates seem very undersized by todays standards. Is this in an area with heavy snow load?? If so I believe the lack of lateral bracing allowed the trusses to deflect out of plane, possibly causing the bent plates.

steve n carol · May 7, 2012

Ray, I don't know where you're at. where I live there are no snow loads. I am allowed 24' span with the 3:12 pitch, 2x4 truss @ 24" O.C.

Your pitch is greater. you can check your local building codes/department, usually online for what is allowed.

I wouldn't just pull them back together, I'd also find the reason, shifting or settling foundations and such.

Glad you found this when you did. keep us updated...sl

JerryS · May 7, 2012

Microburst. As I recall, one spiked a jetliner at DFW several years ago.

Ray · May 7, 2012

I'm in ohio.The rafters are 30ft. 4/12 pitch.

Dr. Ed · May 7, 2012

I have designed a few trusses in the past and these just look underdesigned. The lower chord (the ones pulled apart) is in tension and wants to pull apart -- just like they did. It has nothing to do with the support walls and everything to do with the roof load. Either snow or wind or probably a combination, just overloaded those lightly designed trusses and the weakest link broke. Just pull them together and put on adequate splice plates, like about twice as long, and things will be fine.

The trouble with the local codes boys is that they are cookbook engineers and have never really designed anything so have no experience to judge with. If their book has a misprint all is lost. So much for government control of everything in our lives. They guy that OKed that truss is not there to take the responsibiliy I bet!

gbs · May 7, 2012

looks like the wrong size fastener plates were used, had the proper size been used they would have splintered the ends of the joist as they were pulled apart your simply popped out of the wood

dpendzic · May 7, 2012

Save yourself a lot of money and just pull them back together, support them so they have positive camber, and install a substantial splice assembly, either metal or timber with thru bolts thru the bottom chord.

JDseller · May 7, 2012

You are finding out the hard way that steel grip fastener plates can come apart. I have had many fail in livestock barns. All of mine now are plywood plated.

You can repair yours by jacking up the roof just a little and pulling the plates(top plate on the top of each exterior wall) back together. This will make the boards come back together. They are in tension. Then make strips of plywood (not OBS board). Lap the joint on each side. Apply some liquid nail adhesive and nail the plywood plate to the truss.

I have repaired/reinforced all the trusses on all of my building this way. We had one collapse after the steel grip plates tines/teeth rusted off.

I believe in some states steel retaining fasteners will not meet code for a livestock building. You can read of many hog barns collapsing because of this.

IHC Red · May 7, 2012

Below is an image from software I wrote a while back. The figures should not be taken as "gospel" because I don't have exact dimensions for your trusses, but it will give you a reasonable estimate of the forces in play.

The compession/tension numbers are in pounds with a 50 lbs/sqft static load and trusses spaced at two feet. The loads on the lower members are tremendous. You've received some good suggestions below. In my opinion, if you can get the ends pulled back together (as someone else suggested) and "splice" some 2x4s around the breaks, you may be able to fix it. I would pre-drill and screw them together (maybe even squeeze some construction adhesive in between before screwing). That lumber is going to be dry and pre-drilling will help with splitting. I would also brace along the bottom from truss to truss (lateral bracing) in at least two places preferably three places to keep the bottoms of those trusses from moving from side to side. It's likely that is what loosened up those gusset plates.

Anonymous-0 · May 7, 2012

Right, Micro, thinker just wasn't working properly at that moment.

Cienna · May 8, 2012

I built a pole barn measuring 22' x 40'. Trusses made using 2 x 6's, spaced 5' apart. Horizontal chord measured 26' to allow for overhang. Since I was using used wood, I pieced two shorter 2 x 6's together, and scabbed the joint with a 2 or 3ft piece of 2 x 6. Initially I fastened this together with 12d nails. But after a winter where there was an accumulation of 26" of snow, I notice that there was a hint of those joints pulling apart. So I added six 5/16" bolts to secure the scab to the truss chord. CAN'T go anywhere now!

Anonymous-0 · May 8, 2012

(quoted from post at 19:53:58 05/07/12) Save yourself a lot of money and just pull them back together, support them so they have positive camber, and install a substantial splice assembly, either metal or timber with thru bolts thru the bottom chord.

Exactly.......... Of course that contractor won't tell you that.... Where are you in OH??

Stephen Newell · May 8, 2012

I would build a temporary wall under the sagging side like the other one you have and raise the rafters up to where they belong. Then using heavy tie down straps or a come-along and pull the timbers back together. I would get rid of all those gusset plates and glue and screw a 3' long 2x6 across the joint. It will then never come apart again. I would then go through and replace many of the other gusset plates that haven't failed with Simpson strong ties. It is a heavier steel plate that you attach with screws instead of the little barbs the gusset plates have. I never could see how those would be any good and I refuse to use them and with your story I know I was right.

carpenter · May 8, 2012

I would add: It is easy or should I say not difficult to damage these small gussits by bending the truss while unloading or more likely when handling on job site. Bending the truss sidways.

Also on the majority off buildings the gable end wall is not braced enough. Those 30s have most likely got 4 or five bottem chord load points.

Use latteral bracing at each point securely attached at the gable wall and than up to the roof sheeting.

A very easy fix. Whoever ordered the new trusses with the wrong heal hight should hang there head and get out there check book unless they work by ther hour.

1936 · May 8, 2012

Fire chief friend of mind said when they go in a burning building with the cleat joint they back out real quick - cause the roof is coming down. You can repair and the cover each joint with plywood and nail or screw on the plywood. Much work, but your roof will last.

ChasK · May 8, 2012

I would also brace along the bottom from truss to truss (lateral bracing) in at least two places preferably three places to keep the bottoms of those trusses from moving from side to side.

Click to expand...

As a truss designer, I agree here. 2 X 4 over 30' is not an issue with Ohio ground snow of 20 PSF. (for [i:c6d461a50f]most[/i:c6d461a50f] of the state)
Bottom chord bracing is the key here. 10' O.C. minimum.

"If you brace them they will stay."

You should have 3 rows of bottom laterals tied off with diagonals every 20' of run.

Ken Macfarlane · May 8, 2012

One reason is they fail due to corrosion in the high humidity. Ag buildings don't have to meet the same design standards as regular buildings either. Wider truss spacings on the same spans, one of the reasons more barns collapse from snow load than houses.

farmerjohn · May 8, 2012

Shouldn't the plates that are coming loose have been installed rotated 1/4 turn? I don't know if it would have made a difference for strength or not, I am certainly no engineer.

dpendzic · May 8, 2012

As a Licensed professional structural engineer in two states I would never use those flimsy stamp plates as a joint. anything i design uses thru bolts thru the scabs. As a volunteer fireman we have seen how trusses fail with these skimpy connections---in general in timber construction it is always the connections that are critical in the design and special attention has to be given to them.

Jason the Red · May 8, 2012

One thing that hasn't been said yet (I don't think) is that there should have been 8d nails installed through the plates. The plates never hold with just the teeth biting into the wood. They are designed to be used with nails, not as a substitute.

I also believe I read your contractor is going to tear the roof off. I would try to avoid that by sistering new 2x4s to the existing at one end, then push up the the other end until flush with the other side of the truss. This may fix the problem without the need of tearing into the roof. If the roof looks bad or still has problems after this, then I would tear the roof off. I would say it is worth a try before cutting the roof open.

IOWA NORTHEAST · May 8, 2012

Send your contractor down the road...he is TOTALY PULLING YOUR LEG. That problem is a every day event in confinment livestock buildings with poor ventalation.

Your problrm isn;t even a difficult one. You are talking a day with two guys. One could be a first day on the job rookie as well.

OT- truss rafter problem

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