Broken rafters?

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Old 06-17-19, 05:41 AM
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Broken rafters?

Im trying to understand how rafters work.

Say I have rafter 16" (or larger) apart. One of the rafters breaks in half. Does that constitute and emergency situation? What about when you see rafters pull away from ridge beam... now the only thing supporting the rafter is the decking nailed to it..... is that a failure waiting to happen?

Or does the other rafters take up the slack of the damaged one? Does the roof as a unit provide support?

I ask because I have a cracked rafter in my attic, probably been like that 30+ years, it obviously needs repair but I am wondering if I procrastinate can it cause major damage.
 
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Old 06-17-19, 05:53 AM
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If a 500 lb man was walking over that spot on the roof, and the sheathing was rotten he could possibly fall through. Like you say, it's been that way for 30+ years so it's not an emergency to fix it. And yes, the sheathing and surrounding framing carry the load.

A roofer probably slammed down a heavy bundle of shingles there sometime in the past.
 
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Old 06-17-19, 11:34 AM
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So there is no load on a rafter unless its from above (ie snow, walking etc)?

I would like to try to sister boards to the rafter but I am afraid of nailing or screwing into the ridge beam....

Im assuming if I split the ridge beam while nailing to it, I would be in big trouble, correct?
 
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Old 06-17-19, 01:28 PM
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Rafters hold dead load (the weight of all the building materials currently on top of them) and live load (the weight of anything that would normally/potentially be on it... such as snow). Wind loads are a design factor.

I think your fears are unfounded. Even if the ridge cracks (don't know why it would) it is no big deal. The ridge is generally under compression due to the rafters exerting opposite forces on it. Unless you have hip or valley rafters landing on top of it, the ridge is usually not much more than a spacer.
 
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