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Posted by Wayne Whitney on November 11, 2005, 2:37 pm
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> If the nail is long enough to penetrate the nailing surface by 1/4" or
> so, any longer will make no difference whatsoever.
Well, all the instructions from shingle manufacturers I've read say:
nails embedded 3/4" in substrate OR all the way through the decking.
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> 32" rafter spacing? That must be pretty springy to walk on...
Yes, that was standard practice in 1908, my house has the same thing,
2x4 rafters on 32" spacing. The pitch is 8"12, so mostly I try not to
walk on it.
Cheers, Wayne
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Posted by Duane Bozarth on November 11, 2005, 3:15 pm
Wayne Whitney wrote:
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>
>
> > If the nail is long enough to penetrate the nailing surface by 1/4" or
> > so, any longer will make no difference whatsoever.
>
> Well, all the instructions from shingle manufacturers I've read say:
> nails embedded 3/4" in substrate OR all the way through the decking.
Precisely...OP's question was about whether a longer nail would be
better w/ 1/2" sheathing---answer was "no, not if it penetrates, longer
doesn't matter"...
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> > 32" rafter spacing? That must be pretty springy to walk on...
>
> Yes, that was standard practice in 1908, my house has the same thing,
> 2x4 rafters on 32" spacing. The pitch is 8"12, so mostly I try not to
> walk on it.
Guess they got enlightened by 1914 then...house rafters are on 16"
spacings, same as wall studs.... :) That's about the house roof
pitch--it's actually not an even value--more like 7:12...can stay on it
but is a little iffy on second story...
The barn is on 24", also same as wall studs, but they're 2x6 instead of
2x4. Upper for it is 6:12, lower is 12:12. Don't walk on it... :) Of
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course, at >40 ft off the ground at ridge, didn't do a lot of open
walking on the upper portion either once got the shingles back on. One
real advantage of open-decking is that one can clamber around pretty
nicely while it's open.
The 40 ft boom lift was worth its weight in oil during the
reroofing...we hung a 16-ft long "L" of 2x8's on the front of the
basket, then just landed it on the roof. Gave us a great working
platform w/o having to tote or carry walkboards....
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Posted by Wayne Whitney on November 11, 2005, 3:29 pm
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> Precisely...OP's question was about whether a longer nail would be
> better w/ 1/2" sheathing---answer was "no, not if it penetrates, longer
> doesn't matter"...
Ah, when you wrote "penetrates by a 1/4 inch", you meant goes all the
way through the sheathing and a 1/4 inch farther. I read "goes 1/4
inch into the sheathing", which isn't enough.
Cheers, Wayne
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Posted by Dan_Musicant on November 11, 2005, 4:30 pm
On Fri, 11 Nov 2005 12:32:57 -0600, Duane Bozarth
:Dan_Musicant wrote:
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:>
:> On Fri, 11 Nov 2005 09:57:28 -0600, Duane Bozarth
:>
:> :> No, no I didn't go into all the details. They covered the skip sheathing
:> :> with 1/2" CDX plywood, then 30 lb. felt, then the shingles.
:> :
:> :Maybe that's the problem w/ the nailing...if they didn't fill in the
:> :open spaces in the former open decking they may not have had anything
:> :but the sheathing to nail to for some courses....which will leave any
:> :that are only nailed to 1/2" sheathing w/ not a whole lot of material to
:> :keep them there...
:> :
:> :My inexperience w/ solid decked roofs and composition shingles shows
:> :here...is 1/2" sheathing alone considered enough? (I've only had one
:> :house that had comp shingles and never had to do anything w/ the roof --
:> :everything else I have experience w/ is open decking w/ wood
:> :shingle/shakes.)
:>
:> I believe that 1/2" CDX plywood is code. The estimator told me that it
:> is ample and code even with my skip sheathing, which is approximately
:> 1x5 long boards nailed perpendicularly to the 32" on center rafters and
:> with on average about 5 inches space between the skip sheathing boards.
:> In at least two places a coupld of the skip sheathing boards are
:> actually touching, leaving more than a foot between two adjacent boards.
:> They could (and I thought probably should) have repositioned those
:> boards before nailing on the CDX plywood, but by the time I'd noticed it
:> it was too late. Presumably, the 1.25" roofing nails through the 1/2"
:> CDX is sufficient.
:If the nail is long enough to penetrate the nailing surface by 1/4" or
:so, any longer will make no difference whatsoever.
:32" rafter spacing? That must be pretty springy to walk on...
Yes, it's pretty springy. In some places it's a lot more springy than
others. It's kinda weird. It didn't feel near as springy to me before.
Before it had asphalt shingles over wood shingles, which were nailed to
the skip sheathing. I don't know how many layers of asphalt shingles
were on there. Funny thing is, there are a lot of nail heads sticking
out of the bottom ofa lot of the skip sheathing boards. The skip
sheathing is 1x5 inches and around 20 feet long. The house has two large
dormers, and on the north dormer (which has the lesser slope) there are
hundreds and hundreds of those nail heads sticking out about 1/4" from
the bottom. That makes me imagine that they did a tear off at some
point, probably of wood shingles and instead of pulling out or pounding
down all the nail heads, they pulled up the skip sheathing and turned it
upside down. Those nails are steel and are 1 3/16 inch.
I was thinking of adding some rafters to make them 16" on center, but
didn't. It would have been tough getting them cut right and getting them
in there and I wasn't sure about the installation technique.
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Posted by Michael Daly on November 11, 2005, 4:50 pm
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> I was thinking of adding some rafters to make them 16" on center, but
> didn't. It would have been tough getting them cut right and getting them
> in there and I wasn't sure about the installation technique.
The obvious test of whether the roof framing is adequate is that it has
survived, what, 90 years? That's a pretty good indicator that you don't
really need to fix it. Building codes provide for uniformity and safety
over large regions. Local variations can be safe even if not to code.
I'm not advocating ignoring code, but in your case, the proof is in the
pudding.
Mike
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> so, any longer will make no difference whatsoever.