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Nazareth, PA
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Gaston, Oregon
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 Cracked rafter ends
[#2] Posted: 01/29/2011 - 5:13:09 PM |  |  |
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Brick veneer that's run all the way up to the underside of the rafter tails without the required 3/4" gap?
- Jim Katen, Oregon
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Jim Katen, Oregon
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Nazareth, PA
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Cracked rafter ends
[#3] Posted: 01/29/2011 - 5:28:17 PM | | |
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I'll bet that's it. The thought never occurred to me at the site (or obviously, since). There was quite a bit of expansion in the masonry, as evidenced by four large foundation corner cracks. I think I could have gotten the camera between the plate and the roof sheathing and gotten a pic to confirm it.
Thanks,
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Joe Hancaviz
Nazareth, PA |
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Newberg, OR
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Cracked rafter ends
[#4] Posted: 01/30/2011 - 03:01:29 AM | | |
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That Mr. Katen fella may be a genius. All I could think of was wind uplift before reading his post.
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Brandon
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Canton, Ohio
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Cracked rafter ends
[#5] Posted: 01/30/2011 - 3:49:39 PM | | |
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Could the splitting been caused by a high moisture content of the wood when the house was built? As the rafters dried out, the well toenailed wood didn't move, but split.
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Ezra Malernee
Canton, Ohio
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Belmar, NJ
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Cracked rafter ends
[#6] Posted: 02/21/2011 - 4:49:24 PM | | |
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Upward force from brick veneer might do that, but only if the wood wall moved down (perhaps from shrinkage; somewhat of a stretch).
Wind uplift might do that........though with high roof slope, wind uplift pressure will be quite small (or nonexistent).
Shrinkage might do that........wood does shrink primarily across the grain........which could "pull" the tail against outside edge of wall plate.......still not completely convincing since splits should also then be occurring at the toenails.
The split is occurring at the notch..........similar to splits we often seen at similar notches for old-time floor joists.
My bet is on wind......acting inward against the steep slope.......though it still remains somewhat of a long shot.
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| John F Mann, PE |
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Chicago, IL
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Cracked rafter ends
[#7] Posted: 02/21/2011 - 6:19:48 PM | | |
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I've been staring at that pic since it went up, and I've been thinking it's shrinkage.
I don't think shrinkage in the member means there would also be splits @ the toenails; those little tacks aren't doing all that much; I don't think they'd necessarily cause much split damage where they're located.
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Kurt in Chicago
"If I smell it, it goes in the report".............Phillip Smith...2012
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Belmar, NJ
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Cracked rafter ends
[#8] Posted: 02/21/2011 - 6:49:00 PM | | |
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Although toenails are not all that strong......they have been strong enough to prevent rafter from sliding off the plate, due to outward thrust force at low end of rafter. For high slope, outward thrust force is not very high, though still requires connection to resist.
A more plausible "method" of causing the observed split is force from roof sheathing applied perpendicular to rafters (or vice versa!). Such action could occur from wind applied against relatively large gable endwall........being distributed into the roof sheathing, which attempts to act as a diaphragm........applying out-of-plane force to top of rafters. Wind uplift (to extent it occurs for high slope roof) could then contribute at the same time.
Of course it is usually helpful to know the cause of the problem before developing a repair plan. However, since pinning down the cause (or causes) with certainty may not be likely.......some remedial work should be considered that will address as many of the potential causes as possible.
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| John F Mann, PE |
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Chicago, IL
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Cracked rafter ends
[#9] Posted: 02/21/2011 - 7:14:44 PM | | |
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Well, the shrinkage I was considering was that of the sheathing, the rafter, and any related framing. IOW, all the parts creating some strange stress. I don't see how any single member movement could have enough force to cause that type of split.
Could sheathing, i.e., all those boards and their accumulated movement, cause enough stress to "pull" the rafter a bit and cause the split?
I don't think the portion with the toenails was moving at all, hence, no splits @ the toenails. It split right at the birds mouth, the weakest point in the assembly.
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Kurt in Chicago
"If I smell it, it goes in the report".............Phillip Smith...2012
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Belmar, NJ
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Cracked rafter ends
[#10] Posted: 02/22/2011 - 05:34:37 AM | | |
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For unusual condition (like these split rafters)........comparison with similar construction is useful as a baseline. Many other houses have been built with similar.....or the same.......rafter construction........yet the rafters have not split (at least that is the initial position to consider!). So of course the problem is to figure out what has occurred differently with this house.
Flip side would be that......maybe this HAS happended in many other houses of similar construction and the damage has not been widely reported.
Repair work should be recommended since the splits could easily extend into upper part of rafters, greatly reducing load capacity.......even though, for high slope, snow load should not be large (though this depends on location!).
Steel "mending" plates might be a cost effective repair method.........though reinforcing ("sistering") with new wood is also fine, as long as new wood can be fit tight against existing rafter and roof sheathing. Access appears difficult but not a major problem.
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| John F Mann, PE |
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Lafayette, Louisiana
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Nazareth, PA
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Cracked rafter ends
[#12] Posted: 02/22/2011 - 06:17:08 AM | | |
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This was my recommendation: You should have a qualified structural engineer determine the cause and specify an appropriate repair.
I just emailed to the buyer and asked what the engineer said. I figure the odds are 50/50 that he hired an engineer to look at it.
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Joe Hancaviz
Nazareth, PA |
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Chicago, IL
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Cracked rafter ends
[#13] Posted: 02/22/2011 - 06:57:26 AM | | |
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We always glue and screw 3/4" plywood to both sides of split rafters. It's easy and it works.
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Kurt in Chicago
"If I smell it, it goes in the report".............Phillip Smith...2012
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Nazareth, PA
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Cracked rafter ends
[#14] Posted: 02/22/2011 - 7:40:08 PM | | |
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I got a reply from the buyer. No word on what the structural engineer might have thought as to what caused it.
Hi Joe,
The engineer who inspected the rafters drew up a plywood reinforcement temlpate to repair the 26 affected rafters. Everything else is going quite well, I thank you so much for following up on that concern.
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Joe Hancaviz
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Victoria, British Columbia
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Guelph, Ontario
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Cracked rafter ends
[#16] Posted: 02/24/2011 - 5:37:48 PM | | |
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I do not believe,the brick is an issue,could have been wet rafters{wet wood},the cut was to deep?,rafter is undersized for the span?,nothing to do with the bricks
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