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Old 02-09-2012, 02:46 PM   #16
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Cracked Rafter


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Originally Posted by jasin View Post
We should always worry about anything that is done wrong. We do not want stuff breaking, costing us more in the long run, etc.
There is nothing wrong with the roof nails so there is nothing to worry about.

I do not know why you continue to point out issues that are unrelated to threads and not real issues.

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Old 02-09-2012, 03:32 PM   #17
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Cracked Rafter


This is a slightly off topic discussion about the crack in the rafter. It is aimed at those who might be interested in how a forensic engineer (that's me) goes about analyzing the cause of the crack. This is NOT a guarantee that my analysis is correct, however I thought some of you might be interested in how folks like me go about attempting to determine cause and origin of problems such as this. By the way, normally I require a hands on visit, which of course is impossible in this case.

Step 1: Based on the single photo available, the crack appears in only one rafter. This suggests that the cause is unique to that rafter, and not a generalized overloading condition.

Step 2: That particular rafter has a pair of knots plus some twisted grain between the knots, and the crack corresponds to the knots and twisted grain. Adjacent rafters lack the knots, and coincidentally lack the cracks.

Step 3: There is no evidence in the photo of fire damage, water damage, unusual holes in the lumber, mold, or other exceptional distress to the lumber.

Step 4: The OPS indicates the property is in southern CA, not subject to snow load. There is no evidence of uplift associated with wind load, and there is no indication of impact damage to the rafter.

Conclusion: The most likely cause of the cracking is stress induced by knots and twisted grain, likely associated with dimensional changes due to drying of the lumber.

Appendix: When I do insurance work, I always perform a site visit. In this case, I would examine all of the rafters and associated framing for damage. I would check the foundation for evidence of settlement or movement. I would get a complete history from the owner of loading on the framing, and any impact accidents (trees, cars, meteorites, whatever). All of the evidence gets weighed, and a conclusion is reached.
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Old 02-10-2012, 02:38 AM   #18
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Cracked Rafter


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Originally Posted by mae-ling View Post
Having nails that are too long isn't going to cause any damage in this case.
The nails can shear off if they are not correct length and a higher grade.

Last edited by jasin; 02-10-2012 at 03:15 AM.
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Old 02-10-2012, 02:39 AM   #19
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Originally Posted by puneet View Post
I am guessing that rafter cracked because of the knots. As you already figured out, the existing rafter has no strength left, so it is only useful as a point to attach sister rafters. Personally I wouldn't spend any time gluing it, lagging it or anything else, I would jack it to position, then attach two sisters as you suggested on either side, nailed, screwed or bolted through so they are attached to each other. As Mae Ling said, full length rafters will do the trick. Of course, your 2x4 rafters may be undersized, but that is a different discussion.

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This is good advice. However, Op still needs to check the local building code because in Southern California the use of screws is typically not permitted for most everything structural.

Last edited by jasin; 02-10-2012 at 03:30 AM.
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Old 02-10-2012, 02:44 AM   #20
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Originally Posted by M Engineer View Post
There is nothing wrong with the roof nails so there is nothing to worry about.
Bad advice!

Last edited by jasin; 02-10-2012 at 03:16 AM.
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Old 02-10-2012, 02:47 AM   #21
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Cracked Rafter


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Originally Posted by M Engineer View Post
There is nothing wrong with the roof nails so there is nothing to worry about.

I do not know why you continue to point out issues that are unrelated to threads and not real issues.
Roofing nail length...

Last edited by jasin; 02-10-2012 at 03:14 AM.
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Old 02-10-2012, 06:24 AM   #22
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Cracked Rafter


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Originally Posted by Daniel Holzman View Post
.

Step 4: The OPS indicates the property is in southern CA, not subject to snow load. There is no evidence of uplift associated with wind load, and there is no indication of impact damage to the rafter.
It's not common but it does snow in Southern California.
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Old 02-10-2012, 06:54 AM   #23
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Cracked Rafter


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Originally Posted by jasin View Post
What does this have to do with the OPs question?
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Old 02-10-2012, 07:00 AM   #24
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Originally Posted by jasin View Post
The nails can shear off if they are not correct length and a higher grade.
How can you tell what grade the nails are by this picture?
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Old 02-10-2012, 08:27 AM   #25
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Originally Posted by mae-ling View Post
Having nails that are too long isn't going to cause any damage in this case.
Its a code violation.

Last edited by jasin; 02-10-2012 at 08:30 AM.
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Old 02-10-2012, 08:28 AM   #26
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Originally Posted by M Engineer View Post
How can you tell what grade the nails are by this picture?
No one can tell for certain what grade they are unless they are actually in the attic.

Last edited by jasin; 02-10-2012 at 08:31 AM.
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Old 02-10-2012, 08:34 AM   #27
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What does this have to do with the OPs question?
We are going to ignore other problems because its not the problem he is asking about? Sorry, but no inspector with any honesty would ever do that!
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Old 02-10-2012, 09:36 AM   #28
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Cracked Rafter


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Originally Posted by jasin View Post
We are going to ignore other problems because its not the problem he is asking about? Sorry, but no inspector with any honesty would ever do that!

He did not ask for an inspection. But you always have to bring up other non issues.
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Old 02-10-2012, 09:38 AM   #29
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Cracked Rafter


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Originally Posted by jasin View Post
Its a code violation.
What is the code on roofing nails?
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Old 02-10-2012, 08:02 PM   #30
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Originally Posted by M Engineer View Post
He did not ask for an inspection. But you always have to bring up other non issues.
But that is what we gave him when we evaluated the extent of the problem and purposed solutions to resolve it.


Last edited by jasin; 02-10-2012 at 08:23 PM.
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