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jpezz
Trusses popping loose.
jpezz

I have a 20+ y/o townhouse. The main floor is supported by end-to-end trusses constructed of 2x4s at top and bottom with 2x4 criss-cross supports all held together by press-on braces. One day a while back I noticed that virtually all the trusses' braces where the bottom pieces were attached to each other were popping off and the boards were misaligned. I bought some steel pieces and used them to hold the braces in place with bolts but I am concerned as to the fix and why the trusses would fail. I need expert advice.

I'd upload the images but even though they are proper jpg files, the system says they are not valid:

Note the connecting pieces have bent and come away from the trusses. While this is the worst, it happened on almost all the trusses.


Closeup.

I put a piece of steel on each side both top and bottom and bolted through the 2x4. Basically, they hold the original braces tight up to the 2x4 to prevent the original braces from coming apart. They do not add any strength since the steel pieces (not shown since these are "before" pics) do not cross the 2x4s or hold them together.

What would have caused the problem? I see no problems on the upper 2x4. All the ~46' long trusses rest on the foundation at both ends and rest on a triple 2x10 crossbeam ~32' from one end and ~14' from the other.

MLB Construction
Re: Trusses popping loose.
MLB Construction

i can assure you that this is nothing to worry about. if you look up Simpson Strong Tie -Mending Plates you can see what these products are and that they are not structural at all. they are used for shipping purposes only. it's just a means of helping hold a joint together while the product is being manufactured, moved and installed. once the truss is installed they are useless.

the reason that they are coming out of the truss is because the truss is drying out and the points that are holding it into the truss are slipping out as the wood dries.

no worries

jpezz
Re: Trusses popping loose.
jpezz

Thanks for your reply. I am not a good artist but I this should explain. It appears that the ONLY thing holding the truss together are the plates on the side which hold the crossbeams and the plates on bottom and top which hold the 2x4s that make up the truss (all shown in red). These particular ones hold the two 2x4s that make up the bottom of the truss together. There is one on the bottom of the 2x4s and one on the top. Without them the two parts of the truss would separate horizontally. This is an open truss i.e. a simple 2x4 along the bottom and along the top and 2x4s at angles between them as in

Because the 2x4s are not long enough, where they join together horizontally, they are held together with top and bottom plates as shown. Should they pop off, there is nothing to prevent the truss halves from pulling sideways except these plates. Can you explain to me again that these are not needed? Understand this whole structure is ~46' long. There are 13 of them in this part of the house plus many more that are shorter for the rest of the L-shaped house.

Jack
Re: Trusses popping loose.
Jack

I would worry, trusses have no joints all the parts are butted without the plates there is nothing to hold them together.

Jack

Sombreuil_mongrel
Re: Trusses popping loose.
Sombreuil_mongrel

If all of them are as close to the bearing wall as in your first pic, then there is very little to worry about. To be on the safe side, I'd take them all the way off, and get a box of 1 1/4" screws and mending plates, and screw the plates in. The sharp pin-type fasteners are done in the factory with a press.
The screws would need to be Spax-type or a similar engineered fastener, not drywall screws!
If the problem is occurring in the unsupported middle of a long span, then you need an engineer's help to develop a spec. for remediation, as it is quite serious that the tension member could fully separate, which would cause cascading failures. Oh noes!
Casey

dj1
Re: Trusses popping loose.
dj1

Hammer them back in place, then use deck screws (drill short pilot holes so that the wood won't split) to make sure they don't pop out again.

jpezz
Re: Trusses popping loose.
jpezz
dj1 wrote:

Hammer them back in place, then use deck screws (drill short pilot holes so that the wood won't split) to make sure they don't pop out again.

What I had done was go to Home Depot and bought 3"x3" steel plates about 1/16" thick. They had holes in them. I drilled holes through the existing Tie-Mending Plates and 2x4s and put a steel plate on each side of the 2x4 outside the Tie-Mending Plates. Then I ran a 1/4" bolt with washers through the whole thing and tightened the bolts until they started squeezing the Tie-Mending Plates flat. I then stopped and let the plates adjust to the pressure. The next day I tightened the bolts some more. After a few days, the Tie-Mending Plates were flat and penetrating the 2x4s. The bolts and steel plates remain in place.

Note that I could not find 3x6 steel plates with pre-drilled holes so the plates just hold the Tie-Mending Plates in place rather than providing their own connection to both pieces of 2x4 but I was looking for a quick fix. Should I see further strain in the Tie-Mending Plates, I will remove my quick fix and replace everything with long pieces of angle iron bolted into both 2x4s.

Note that the upper 2x4 Tie-Mending Plates never came loose and I have done nothing to them. This was all done about 2 years ago.

Now, I have begun to wonder why this happened in the first place and, what, if anything, I should be concerned about. Since all 92 townhomes in our subdivision were built using these trusses, it makes me nervous. Those residents who are also amateur workmen never saw anything like this on their trusses.

dj1
Re: Trusses popping loose.
dj1

Sounds good to me.

Maybe you can start a truss repair business in your neighborhood.

Mastercarpentry
Re: Trusses popping loose.
Mastercarpentry

Those truss plates perform a structural function and is loose, they need repair. The top chord of the truss is under compression (pushing together) loads so those don't tend to loosen. The bottom chord plates are under a tension load so they tend to pull apart. There are no alterations or repairs allowed without an engineered drawing, but here's a description of what I've always got. Clamp the plates together with 2X material and a C-clamp and the truss sandwiched in between, tap the clamped assembly to ensure they're tight, remove the clamp setup, cover both sides with a mending plate as large or larger than the truss plate and fasten that with 8D galvanized nails. You do both sides so that they remain equal in strength; do only one side and the other side will loosen. Can't remember the specifics of how many nails have to go in each member, just use common sense and don't split the wood from too many.

With this being a systemic issue rather than isolated damage and with the home relatively new, I'd be checking with my attorney to see if the truss maker is liable- chances are that they will be. They were probably built to the minimum required specs which they will claim indemnifies them but unless they can prove an outside force or element damaged them then they are still responsible for what is now a faulty product. If you take this approach get yours fixed before others discover their own problems as many truss companies have been sued out of business leaving those with the faulty products stuck without recourse. Get your claim handled before that happens.

#3 SYP is sometimes used in truss construction and it's a poor choice and I've seen plenty of SYP's known and normal warping pull joints apart over time. #2 SYP can be nearly as bad and that's the best grade you get around here from the truss companies. I've seen where hard grain or knots have bent many of the 'spikes' on the plate which were supposed to penetrate and hold but didn't and were shipped out that way.These are another example of something working on paper but performing differently under real-world conditions and that's why I'm a staunch traditionalist who prefers solid, single piece joisting and rafters over trusses. The old way still works as good as it always has, the 'new' way sometimes doesn't. Components which cannot be easily replaced if they fail must simply be the best.

Phil

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