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chris0914 01-25-2009 08:36 PM

Broken Roof Truss
After looking around in my attic i noticed that one of the roof trusses was starting to twist and crack in the middle of it. Anyone have any suggestions on how to fix this. I read someone where that u can sister a 8' 2x6 along the side of it of take a piece of l channel steel and lag it into the wood to try to straighten it out. Is there anyone that can help in this issue and help would be great.

Termite 01-25-2009 09:33 PM

First (and no offense intended) let's make sure your terminology is correct. A lot of people mistakenly confuse roof elements that are framed in the field (such as rafters, purlins, ridges, hips, valleys, and support members) with trusses, which are made in a factory and delivered to the jobsite.

Assuming we are in fact talking about trusses...
Breaks can usually be repaired fairly easily. If it were new construction and it broke, the truss supplier would provide an engineered, computer-generated repair showing exactly how to repair the break. Different parts of the truss do different things and are subjected to various forces. Since you're looking at work that has probably been there for a while, the truss company probably isn't an option. Therefore, your best bet is to involve a structural engineer to design an adequate repair.

There is no one-size-fits-all repair for broken truss chords.

That being said, the vast majority of breaks can be repaired by sistering the same size of dimension lumber to the side of the break, or even both sides. The sistered member usually is several feet long, and construction adhesive and A LOT OF NAILS is nearly always specified. It isn't uncommon for them to require three rows of nails only a few inches apart, from each side.

In all my years as a building inspector and all my years in the engineered lumber/truss business before that, I have NEVER seen any reputable engineer or truss company recommend the installation of a piece of steel to reinforce a broken chord. That would be ridiculous overkill, and some parts of a truss are actually designed to deflect under load.

chris0914 01-26-2009 04:44 PM

Thank you for the help I donot thing that I am using the correct phrase after reading your reply. I guess I am not dealing with a Truss at all, this was not factory made and I want to call it now a rafter but donot know if that is even correct. It is a 2x6 that runs from the headers on the wall to the top of my roof and meets with a board that runs the length of my house. On the other side of that board is another 2x6 in line with the first on runing to the other header on the opposite wall. So now I hope i am calling it the right this by saying a rafter but probaly not. Anywas thank you for the reply I am going to use ur advice and sister to 2x6s on both sides on the broken board. Any suggestions on how long this is suppose to be the original board that is there is 14 foot long and the crack is 4' of the header.

chris0914 01-26-2009 06:55 PM

and also one more question if i cant but the sister board up to the plywood because of the nails from the shingles coming through do i just put it up as high as i can or do i cut the nails down then get it up against the plywood

joel v. 01-26-2009 08:51 PM

A rafter is always going to be over engineered so you could likely sister a 2x6 with a 2x6 ripped down to 4.5 inches. One on each side. If it was me I would run it about 3-4 feet past the crack so 10-12 feet in total. That's just me though. Take a longest level you have (atleast 4 feet, preferably 6') and put it on the broken rafter and get it (the rafter) pushed up far enough so there is no rocking and no gap with the level on it

Termite 01-26-2009 09:29 PM

Chris, it sounds like we're talking about a rafter.

It would really help if you could post a picture of the damaged area, showing the roof framing surrounding it so I can tell what we're dealing with.

With a rafter, you can usually get away with sistering one new rafter up against the cracked one. You can carefully clip or bend the nails that protrude down through the sheathing, but remember that they're holding your roof shingles on so you don't want to drive them upward. Joel V's idea about ripping the edge off of a 2x6 to accommodate the nails isn't a bad idea...Any wood you add will certianly strengthen the rafter.

Although I still maintain it is best to consult with an engineer...
You can probably fix this with a 12' 2x6 attached to the damaged rafter with construction adhesive (liquid nails) and 10d box nails. Do two rows of nails with a nail every 12" along the length, so they're about 6" apart staggered top and bottom. The longer the repair board is, the better.

slummy 11-24-2010 11:59 PM

several rafters cracked
My 2 x 4 rafters are 24" on center. They support 3 layers of shingles, a layer of cedar and a layer of pine sheathing - that's a lot of weight. So much so that it has cracked several of the rafters.
After consulting buddies of mine that each have twenty plus years of roofing experience I am going to follow these directions;

First replace floor joists from end to end (the entire span in all structural framing is key) Use nail gun and circular for this
Step 2 lay a 2x6 plate across and above the entire span of my attic floor / downstairs ceiling joists
Step 3 climb step ladder, use speed square to measure pitch of roof, set chop saw and cut base plate side of 2x6 sister rafter
Step 4 Have a friend hold base plate flush to floor (I don't need a seat cut - you might)
Grab other end of sixteen foot 2x6 climb step ladder use square to draw a line down from my 1x8 pine ridge plate, cut 2 x6 - lay sister rafter on the ground then
Step 5 use a four foot level against cracked rafter and good rafter to inspect the difference in pitch (get a mental picture of how the good rafter looks)
Step 6 jam a kneewall sized 2x6 between new base plate (step 2) and cracked rafter to take the sagg out of the roof (check pitch with level)
Step 7 from end to end nail up the sister rafter that I just cut both sides of with the nail gun my buddy lent me.

Step 8 remove kneewall from new 2x6 rafters and put them under good 2x4's

Now it's strong enough to hold me while I ripit and install a galvanized roof in late spring

Peace out y'all

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