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Champaign, Illinois
Posts: 511
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Kenmore, WA
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Re-education in 3 tab nailing
[#2] Posted: 08/01/2009 - 08:37:51 AM |  |  |
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I can't prove the mis-placed nails will cause the shingle to leak or not. My educuated guess is that mis-placed nails will not cause leakage. If the nails stand proud of the shingle, then the strips may not seal as well.
According to the NRCA Roofing manual, if the shingles seal, then nailing is actually secondary and mis-placed nails aren't critical to the shingles' performance.
Regardless, I still write things up that aren't instaled according to the spec's.
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Randy Navarro
http://www.thecompleteinspection.com |
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Allen, Texas
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 Re-education in 3 tab nailing
[#3] Posted: 08/01/2009 - 10:09:49 PM | | |
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Seems like the last GAF training I went to said the nail should not be in the tar strip due to detrimental effect on wind damage/blow off attributes... But it is late and things are getting fuzzy.
As long as the nails are covered by the shingle above I can't see it causing a leak.
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Jim Luttrall
Mr. Inspector.net, Inc.
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Champaign, Illinois
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Re-education in 3 tab nailing
[#4] Posted: 08/02/2009 - 3:15:29 PM | | |
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If the nails are to high, like in the tar strip, that means that the nail is probably not going through the shingle on the lower coarse. If the shingle doesn't have the nail in the back if it, what could happen? Could a group of shingles somehow float, especially if the sheathing expands/contracts?
Another question:
When water wicks back up through the shingle, is this called capillary effect?
Thank for all your help.
Frank
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Collins, NY
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Re-education in 3 tab nailing
[#5] Posted: 08/02/2009 - 4:55:00 PM | | |
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I would think that the first roof would leak, shingles of any kind should not be on a slope that low without a complete cover of IWS. The spongy sheathing is likely due to the leaking low slope roof or they used the wrong sheathing material or failed to install the proper clips.
Tom
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Tom
http://clearcreekhomeinspection.com/
Life is tough enough as it is, it's tougher when your stupid. Don't do stupid things.
Dr Joe Lstiburek |
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Needham, Massachusetts
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Re-education in 3 tab nailing
[#6] Posted: 08/02/2009 - 5:36:51 PM | | |
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Personally, in areas that are not hurricane-prone, I don't think anything happens when you nail through the tar strip, -at least not at pitches under 6:12, which is most roofs I see. At pitches steeper than that, you might start to see shingles slide down toward the gutter.
And though I've never tested it under controlled laboratory conditions, I am willing to go on record saying that no measurable amount of water can be drawn up through an asphalt shingle through capillary action unless you leave one soaking in standing water for a day or more, and even then I seriously doubt it would be an appreciable amount. If the shingles are saturated, or the wood beneath them is wet, the water is coming from somewhere else.
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Jimmy
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West Pittston, PA
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Jefferson Twp., NJ
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Collins, NY
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Re-education in 3 tab nailing
[#9] Posted: 08/06/2009 - 05:37:51 AM | | |
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Kyle,
Thanks for code cite, but in my experience, and at this lattitude, shingles on a 2/12 pitch tend to wear out before they seal down. I've seen several instances where the area under the tabs is more than just a little wet after a light rain, the worst was wet after a heavy dew.
Tom
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Tom
http://clearcreekhomeinspection.com/
Life is tough enough as it is, it's tougher when your stupid. Don't do stupid things.
Dr Joe Lstiburek |
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