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Greetings,
I have been called on to explain a roofing problem and I need help!
The details:
5/12 roof pitch
16″ oc 2×8 rafters
5/8″ cdx sheathing
Bituthane entire roof deck
Continuous venting
R-30 ceiling insulation
Fiberglass shingles nailed with Senco 1-1/4″ nails
The roof is oriented with the planes facing east & west. fully 25% of the nails on the east face have popped 1/4″ or more. They are still firmly embedded. There is some popping on the west face but not as much. The roof was nailed down in cold weather.
Anyone have a similar experience? Any ideas?
Thanks,
Jon Thompson
Shutesbury, Massachusetts
Replies
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There is a little known cult of galvanization fanatics whose offspring begin life as roofing nails. One of the noteworthy aspects of their religion is that they rise up to worship the morning sun. An exorcism in the light of the full moon is called for. Unfortunately you'll have to wait almost a month again now, fast and pray in the meantime.
Seriously now.....
The clue for me is that it was installed in the cold. Was there any frost on the plywood holding up the shingles that melted out later. In other words, maybe the shingles were not nailed tight to start with rather than nails popping, maybe the shingles are settling down on them. Sometimes the shingles have a little wrinkling in the cold that doesn't settle out either right away too.
Or maybe a UFO with electro-magnetic power cells flew over the east side of the roof and sucked the nails up.
NO - I've got it now - The owner is a mad scientist descended from Tesla. He's been experimenting with electro-propusion. You should've used plastic screws.
*Piffin, You're right about the cold. In addition, there could have been low pressure on the gun from a sluggish compressor or a sticky gun because of frost in the cylinder. On the other hand, it's a lot more common for a pneumatic nailer to shoot nails right through cold shingles than for them to stop short. Whatever, gun nailing is poor practice in cold weather.
*I still hand nail. My personal best was 28 squares in a day on a 4/12 with three tabs so it never was worth the investment in machinery that does always work right.
*The nails were popped at installation.Bad install.near the stream,aj
*JonIs this a cathedral roof? Can you see the underside anywhere?I have seen lots of nail popping on roofs that have moisture problems due to wintertime condensation.Please don't ever fool yourself into thinking that continuous ridge and soffit vent means anything.Air exfiltrates out holes in the top of the house and hits the cold roof, then the moisture the air was carrying gets all inclined to stick to the roof and stay awhile. I call this phenomena "condensation." Even if the cold air is coming up through the soffit and under the sheathing it can still condense.This wetting and drying of the plywood causes the nails to head for the sky.-Rob
*I've seen these nails popping up myelf. It isn't from guns. It is from expansion and contraction. Shingles are supposed to be spaced. How many of you space your shingles? Occassionally, the orientation of the roof, to the heat of the sun causes severe heat/cold swings that cause the shingles to grow and buckle. The continous up and down motion of the buckleing work the nail loose.Solution/prevention: Space your shingles while laying them in cold weather.Or maybe its the 5/8 with bitch a thane. Overkill! The supply Gods are revolting.blue
*R Suzie,I have seen that too but on uninsulated roofs. This one has R-30. No frost getting to it from under.
*Jon,I believe that the nails are too short. With the 5/8" sheathing, bituthane, and the thickness of the shingles, the 1 1/4 nail doesn't fully penetrate the sheathing. It is my belief that without this penetration, you are prone to the situation you describe.Red dog
*It's probably caused by the nails, plated nails tend to pop.The plated nail has a smooth shank which can lose it's withdrawal resistance. The freeze-thaw cycle will work plated nails out of a roof deck within a few yrs. Combined with the fact it was shot in the cold they may have not been seated properly to begin with and they would start popping sooner JAO, Barry
*Barry, you might have something there. in normal temps the nail acts as a wedge, sliding into the grain of the wood by displacing grain which grabs back at it again. If the ply wood has a little frozen moisture in it, it is more likely to shatter. The nail acts more like a shotgun blasting a hole through that can be larger than the nail, letting it loosen up. I'm serious this time guys, honestly.
*What a bunch of nonsense....
*hey Rob, > Please don't ever fool yourself into thinking that continuous ridge and soffit vent means anything.getting off topic but you really think soffit vent & ridge vent is useless?chrs, GO
*Rob hasn't seen the one I saw where there was 1/2" of ice clinging to the inside of the sheathing from no vents. It was very well insulated.
*Piffin, looking well insulated means nothing if the attic is full of ice. Unless the frost is from a leaking roof?That frost is the result of warm moist air from inside the insulated envelope leaking through to the attic. Venting the attic to eliminate (hopefully) the ice will only increase the loss of heat & humidity from inside the house. Seal the leaks, don't create more. Joe H
*I already solved that problem twenty years ago. It had r-30 fibreglass but no vapor bar. No roof leaks. I installed ventilation and caulked around the cieling lights. Recommended new cieling paint but it never got done. Problem went away.
*nails a little too short... cold weather...smooth shank...shingles bridging.. all add up to some pops..the nail should be imbedded one inch in solid wood or stick stick thru the sheathig be at least a quarter inch to get the design withdrawl resistance..the vent / no vent has NOTHING to do with itb but hey, whadda i no ?
*George, I don't think it is useless, but I do think it is NOT a cure all. I have many people calling me about problems that were not fixed by the installation of ridge and soffit vents. The installation of ridge and soffit vents has gotten to become "synonymous" with quality and craftsmanship. Their presence seems to embody much more prestige than they ought to. Randomly ventilating roofs (and now I am getting calls about walls) may fix the problem, it may not. The problem is that there are many mitigating factors, and many half-truths.ASHRAE even says the validity of roof venting is based on flawed research.I have, in fact, FIXED ice damming by plugging the ridge and boot vents on some houses. I can do this because I am finding and understanding the mitigating factors. The problems that show up at the roof are not necessarily caused there.Piffin, caulking around the ceiling lights is considered air sealing.I did a fairly good job of describing the problem in this thread:http://www.jlconline.com/cgi-bin/webbbs/science/webbbs_config.pl?read=2686-Rob
*http://www.jlconline.com/cgi-bin/webbbs/science/webbbs_config.pl?read=3942
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Greetings,
I have been called on to explain a roofing problem and I need help!
The details:
5/12 roof pitch
16" oc 2x8 rafters
5/8" cdx sheathing
Bituthane entire roof deck
Continuous venting
R-30 ceiling insulation
Fiberglass shingles nailed with Senco 1-1/4" nails
The roof is oriented with the planes facing east & west. fully 25% of the nails on the east face have popped 1/4" or more. They are still firmly embedded. There is some popping on the west face but not as much. The roof was nailed down in cold weather.
Anyone have a similar experience? Any ideas?
Thanks,
Jon Thompson
Shutesbury, Massachusetts