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Old 01-20-2013, 12:07 PM   #1
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Rafter Ties


Hello,

DIYer here, so please excuse or correct my terminology. My attached garage is approximately 25' x 19', built in 1968 in California. The roof rafters run in the 19' direction and are 2x6 24"OC. There are four 2x4 rafter ties spanning the 19' length, and the previous owner used them for storage, obviously a problem, badly sagging and cracked. There is a 2x6 running down the center of the garage. I was able to sister in two 2x6 boards next to two of the 2x4 rafter ties, jack up the old ties, and nail them together every foot. The two I was able to fit in we're in a part of the garage adjacent to the house such that I could slide the 2x6 into the attic as far as I needed, then slide it back in place next to the old 2x4 on the top plate.

Further down, the other two rafter ties sit on the top plate that is a part of two outside walls (no longer adjacent to the attic). I cut the new 2x6 ties slightly shorter so that only about an inch and a half will sit on the top plate on either side. Even so I cannot fit the new board around the other rafters no matter what I do. The board is just too long! What do people do in this situation?

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Old 01-20-2013, 02:17 PM   #2
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Rafter Ties


All,

I wanted to add a few photos. These show the two successfully sistered rafter ties, and the one that I cannot get in.


Thanks,
John
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Rafter Ties-img_1644.jpg   Rafter Ties-img_1645.jpg   Rafter Ties-img_1646.jpg   Rafter Ties-img_1647.jpg   Rafter Ties-img_1648.jpg  

Rafter Ties-img_1649.jpg  

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Old 01-20-2013, 02:55 PM   #3
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If it's a case of sistering a damaged tie, you don't have to go top plate to top plate with the new piece. You can stop it short of each top plate by a foot or so, as long as it's well-nailed to the existing timber. This is because the bending stress is greatest near mid-span, and tails off towards the supports..
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Old 01-20-2013, 03:13 PM   #4
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Thanks Tony. I might have to resort to that, although the 2x4s are in really bad shape. I also bought a few more 2x6s, which I was going to attach to the remaining rafters for good measure. Surely people do this to garages post- construction all the time right? Do they bow the 2x6 boards to install them or something?
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Old 01-20-2013, 03:38 PM   #5
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You can cut them 3" longer than the inside wall span measurement, then slide it to get minimum 1-1/2" bearing on both walls per minimum code; "R802.3.1 Ceiling joist and rafter connections. Ceiling joists and rafters shall be nailed to each other in accordance with Table R802.5.1(9), and the rafter shall be nailed to the top wall plate in accordance with Table R602.3(1). Ceiling joists shall be continuous or securely joined in accordance with Table R802.5.1(9) where they meet over interior partitions and are nailed to adjacent rafters to provide a continuous tie across the building when such joists are parallel to the rafters." From; http://publicecodes.cyberregs.com/ic...002_par018.htm
Follow the links in that above for the very important connection of tie/rafter as you have.

Be sure to cover the paper faced insulation as per manufacturer in an unheated garage against fire, pp. 29-30; https://docs.google.com/viewer?a=v&q...sMKTgMsl7TruSQ.

Gary
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Old 01-20-2013, 03:43 PM   #6
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Your also going to have to now go back and patch any place where those big holes were cut out around the joist.
Is there baffles behind that insulation a ridge vent and soffit vents?
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Old 01-20-2013, 03:55 PM   #7
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Thanks to both, it's good to see the actual code. Is the insulation really doing anything in the garage? The previous owner installed it. I will patch the sheet rock around the joists as well. I am not seeing any vents other than one up near the ridge.
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Old 01-20-2013, 10:04 PM   #8
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Insulation on rafters is not doing much... the paper facing is slowing the vapor drive to outside. If anything, it may be slowing the moisture from leaving after a wet vehicle parks in there. If the house is connected at the furnace/HWT wall (since the gable above the rafter ties is drywall-- there is your fire barrier) you may not be required to drywall the roof or side/end (vehicle door) wall or even patch any holes per code. Would look better, though. Install a weather-stripped access door in that attic firewall, to keep a garage fire from catching your house attic on fire. I have a code reference somewhere, but here is CA's; http://publicecodes.cyberregs.com/st/ca/st/index.htm

Gary
PS. I would patch around the B-vents (gas exhaust), both of them, where they come out of the fire-wall (house common wall).
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Old 01-20-2013, 10:26 PM   #9
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What exactly are you trying to accomplish? If you are trying to tie the rafters to keep the walls from thrusting outward, You need at least a 2 x 8 that is bolted to each rafter with a 5/8 bolt and large flat washer on each end. Nails will not serve the purpose.

The 2 x 8's could be up slope 1/3 the length of the rafter Maximum to give you room to work.
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Old 01-20-2013, 10:33 PM   #10
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Gary,

Thanks, I was able to get them up there today! I agree with all your other comments also - I think I am going to get rid of the insulation as well.

Thanks again!
B/R,
John
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Old 01-20-2013, 11:33 PM   #11
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Glad we could help, John! Insulation is just taking up space there, even blocking any fascia gaps contributing to air flow.LOL.

Under the CA Building code (from the supplied link); #18: http://publicecodes.cyberregs.com/st...?bu2=undefined

Find your slope, the amount of fasteners depends on span and snow load (or none) from chart: http://publicecodes.cyberregs.com/st...?bu2=undefined

Jagans, why would he require a 2x8 at each rafter (rather than every 4', per code) and bolts, or were you thinking of another code? If he couldn't get the quantity of nails required without splitting the 2x6's... a bolt, but the existing 2x4 may have enough, or not. If no drywall, why 2x8's at every rafter?

Gary
PS. I would add a tie or two from the c.j./r.t. to the rafter above at the garage door opener, due to the weight of the door when opened...if doubling that one doesn't help.
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Old 01-21-2013, 10:45 AM   #12
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Gary, you are right, I should have said every other rafter. I said 2 x8 because of the span. He should have a king post in the middle, Bolted, also.

Bolts and large washers should be used because wood has very low resistance along its grain, and the bearing area of a nail is about an 1/8 inch.
Split ring connectors would be even better.
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Old 01-21-2013, 12:40 PM   #13
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Quote:
Originally Posted by jagans View Post
Split ring connectors would be even better.
Difficult to fit on a DIY job, though.
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Old 01-21-2013, 12:51 PM   #14
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Hi Tony,

Im not sure how the type of job has anything to do with "Fit". Its about engineering. Gravity, and dead load does make exception for "Type of project" as far as I know. It drives me nuts when I describe how a certain detail should be executed vis a vis weatherproofing, and I get "Well is it residential or commercial" as if rain knows the difference.

Split ring connectors come in all sizes, and can be made up pretty easily, for that matter, but large bolts and flat washers should suffice on this job. You simply tighten the bolts till the washers dent the wood.
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Last edited by jagans; 01-21-2013 at 12:56 PM.
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Old 01-21-2013, 04:08 PM   #15
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Quote:
Originally Posted by jagans View Post
Hi Tony,

Im not sure how the type of job has anything to do with "Fit". Its about engineering. Gravity, and dead load does make exception for "Type of project" as far as I know. It drives me nuts when I describe how a certain detail should be executed vis a vis weatherproofing, and I get "Well is it residential or commercial" as if rain knows the difference.

Split ring connectors come in all sizes, and can be made up pretty easily, for that matter, but large bolts and flat washers should suffice on this job. You simply tighten the bolts till the washers dent the wood.
Hi Jagans.

In your third sentence, I wonder if you meant to write

"Gravity and dead loads does not make exception for "Type of project".

If so, I agree. I also agree that split-ring connectors have a far higher shear capacity than bolts or nails due to the much larger area of timber the rings bear against. However, the OP would need to get the bit for boring and cutting the grooves, which has to match exactly the rings used.

I don't know how knowledgeable the staff at Lowes or hd are, but our local DIY people wouldn't know a split ring from an axe.
This is a DIY site and has a lot to do with the tools and skills people have and in many cases a less-than-ideal standard will suffice.

So bring on the 5/8" bolts, or even a few 4" nails driven into strategically placed pilot holes.

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