[RE-wrenches] L feet no flashing in shingle roof

Bill Hoffer sunengser at gmail.com
Mon Jul 2 16:08:49 PDT 2012


Mark

Lags for me are old hat after using the newer structural screws.  I get
them local from www.screw-products.com although I know there are more
companies out there that make them for the Structural Insulation Panel
industry.  Thinner than lags with comparable strength, they drive easy with
no predrilling, and are less likely to blow out a truss.  Come in many
different lengths and use a special star head with a built in washer.  I
use thick butyl tape on the foot and a small rubber washer on the screw
head , together they work great!  If you want a little more security a dab
of the appropriate sealer in the foot slot before finally tightening it
down works too.  Only way to go on corrugated metal roofs where there is no
real option for flashing.

Bill

On Mon, Jul 2, 2012 at 3:40 PM, <mark at hurshtown.com> wrote:

> My 18V Milwaukee cordless hammer drill has no trouble driving a 5/16" lag
> into anything I've ever encountered.
> If you put the lag anywhere near the middle of the rafter it won't split.
>  If it splits, it must be some cheap stuff from Home Depot.
> Only an engineer with no practical experience would insist on a pilot hole
> and the resulting reduction in holding strength.  I'm assuming the IBC
> consists of a bunch of bureaucrats that value control over common sense.
> In this instance flashing offers no benefit, and may even be
> counter-productive if incorrectly installed and it causes rain to collect
> under it.  My experience is in northern Indiana where it does rain and the
> wind does blow.  (Record 91 mph winds last Thursday.)  Less severe weather
> than Michigan, but close.
> I use the best silicone caulk Menards has to offer.  I've never worried
> about compatibility.  It definitely won't dry up and crack away like the
> black roof cement some swear by and insist on.  15+ year old silicone caulk
> is yellowed a bit but that's the only change.
> If the silicone and shingle aren't getting along, I've never heard them
> complain.
>
> Mark
> (Disclaimer: Portions of the preceding are the opinions of the author.)
>
> -------- Original Message --------
> Subject: Re: [RE-wrenches] L feet no flashing in shingle roof
> From: Dave Click <daveclick at fsec.ucf.edu>
> Date: Mon, July 02, 2012 10:29 am
> To: re-wrenches at lists.re-wrenches.org
>
> I always thought that installing lag screws was tough enough with pilot
> holes- I should hit the gym. I'm not a structural PE, but I think that
> not drilling pilot holes violates the American Wood Council's National
> Design Specs and therefore violates the IBC too. I would imagine that
> you'd be much more likely to split your trusses. IBC also requires
> flashings be used but at least around here inspectors never ask for it
> (which makes sense- as you all know, Florida never sees wind or rain,
> and definitely not at the same time). What silicone do you use that's
> compatible with asphalt shingles?
>
> DKC
>
> On 2012/7/1 21:13, mark at hurshtown.com wrote:
> > In my 20 year experience of lagging down L feet on shingle roofs in
> > Indiana with a good dollop of silicone caulk under the foot, I've never
> > had an issue. No pre-drilling, just drive the lag home. Drilling a hole
> > first is not necessary, and reduces holding strength. No reason to make
> > a science project out of it and increase cost and labor.
> >
> > Mark
> >
> > -------- Original Message --------
> > Subject: Re: [RE-wrenches] L feet no flashing in shingle roof
> > From: Drake <drake.chamberlin at redwoodalliance.org
> > <mailto:drake.chamberlin at redwoodalliance.org<drake.chamberlin at redwoodalliance.org>
> >>
> > Date: Fri, June 29, 2012 3:09 pm
> > To: RE-wrenches <re-wrenches at lists.re-wrenches.org
> > <mailto:re-wrenches at lists.re-wrenches.org<re-wrenches at lists.re-wrenches.org>
> >>
> >
> > Hi Jay,
> >
> > There is no room for flashings. The L feet will go very close to the
> > skylights and the flashing would hit the edge of them. Plus there is
> > an existing array that was done by another installer that is done
> > with L feet only. The new array would be higher.
> >
> >
> >> And given that we have really good off the shelf approved flashed
> >> feet, why would you use anything else?
> >>
> >> My 2 cents,
> >>
> >> Jay
> >>
> >> peltz power
> >>
> >>
> >> On Jun 29, 2012, at 5:16 AM, Glenn Burt wrote:
> >>
> >>> We have used a variety of sealants over the years, and determined
> >>> simple Henry roofing cement is the best product for use on comp
> >>> roofing.
> >>>
> >>> We also used to bend our own L-foot flashing, which we cut from
> >>> standard Al coil stock (before all the manufactured options were
> >>> available). This might be a good option for you in this case.
> >>>
> >>>
> >>>
> >>> Glenn
> >>>
> >>> *From:* re-wrenches-bounces at lists.re-wrenches.org
> >>> <mailto:re-wrenches-bounces at lists.re-wrenches.org<re-wrenches-bounces at lists.re-wrenches.org>
> >
> >>> [mailto:re-wrenches-bounces at lists.re-wrenches.org<re-wrenches-bounces at lists.re-wrenches.org>]
> *On Behalf Of
> >>> *Drake
> >>> *Sent:* Thursday, June 28, 2012 6:40 PM
> >>> *To:* RE-wrenches
> >>> *Subject:* [RE-wrenches] L feet no flashing in shingle roof
> >>>
> >>> I'm quoting a job that has an existing array with L feet bolted
> >>> down to a shingle roof with no flashings. I want to match the
> >>> height of the existing array. Also some modules are being worked
> >>> in around skylights where it is unlikely that room would be
> >>> available for flashings to center over rafters.
> >>>
> >>> I've always used flashings. Would it be completely crazy to
> >>> follow suit of the existing array and bolt L feet straight to the
> >>> shingle roof with good roof sealant? If so, how would you seal it?
> > Drake Chamberlin
> > ATHENS ELECTRIC LLC
> > OH License 44810
> > CO license 3773
> > NABCEP Certified PV
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-- 
Bill Hoffer PE
NABCEP Certified Solar PV Installer™
Sunergy Engineering Services PLLC
2504 Columbia Ave NW
East Wenatchee WA 98802-3941
SunEngSer at gmail.com Cell:(509)679-6165
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