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

benn kilburn benn at daystarsolar.ca
Mon Jul 2 18:19:10 PDT 2012 

Mark,
You wrote, "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."
Drilling a properly sized and depth pilot hole willŠ
-reduce the possibility of the rafter splitting,
-reduce further opening an existing split and
-reduce the chance of splitting a rafter when lagging directly into solid
knot that will surely split without a pilot hole
...and if the whole roof is built with the same 'cheap stuff from home
depot' then wouldn't you want to reduce the chance of every
penetration/rafter splitting and compromising the integrity of the
installation?

A properly sized pilot bit will not reduce the pullout or shear strength of
a lag bolt.  There are charts for reference for different types of wood.

 Anyone who works with wood and where splitting, structural or aesthetics
are a concern (carpenter, cabinet maker, framerŠrooftop PV installer) should
know that wood splitting is significantly reduced when a pilot hole is used.
It is a 'best practice' method.

I don't sweat over using just L-feet, because when I do I'm confidant that
I'm using an approved sealant and enough of it to make each hole I drill in
the roof leak-free, but I will not deny that a flashed roof penetration is a
superior and first choice method.

Cheers,
Benn

DayStar Renewable Energy Inc.
www.daystarsolar.ca
780-906-7807 
Certified Construction Electrician Solar Photovoltaic Systems Certified
Certificate # 0007S
HAVE A SUNNY DAY

On 02/07/12 4:40 PM, "mark at hurshtown.com" <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>>
>     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>>
>
>     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>
>>>     [mailto: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
>     ------------------------------------------------------------------------
>     _______________________________________________
>     List sponsored by Home Power magazine
>
>     List Address: RE-wrenches at lists.re-wrenches.org
>     <mailto:RE-wrenches at lists.re-wrenches.org>
>
>     Options & settings:
>     http://lists.re-wrenches.org/options.cgi/re-wrenches-re-wrenches.org
>
>     List-Archive:
>     http://lists.re-wrenches.org/pipermail/re-wrenches-re-wrenches.org
>
>     List rules & etiquette:
>     www.re-wrenches.org/etiquette.htm
<http://www.re-wrenches.org/etiquette.htm>
>     <http://www.re-wrenches.org/etiquette.htm>;
>
>     Check out participant bios:
>     www.members.re-wrenches.org <http://www.members.re-wrenches.org>
<http://www.members.re-wrenches.org>
>
>
>
> _______________________________________________
> List sponsored by Home Power magazine
>
> List Address: RE-wrenches at lists.re-wrenches.org
>
> Options&  settings:
> http://lists.re-wrenches.org/options.cgi/re-wrenches-re-wrenches.org
>
> List-Archive: 
http://lists.re-wrenches.org/pipermail/re-wrenches-re-wrenches.org
>
> List rules&  etiquette:
> www.re-wrenches.org/etiquette.htm <http://www.re-wrenches.org/etiquette.htm>
>
> Check out participant bios:
> www.members.re-wrenches.org <http://www.members.re-wrenches.org>
>
_______________________________________________
List sponsored by Home Power magazine

List Address: RE-wrenches at lists.re-wrenches.org

Options & settings:
http://lists.re-wrenches.org/options.cgi/re-wrenches-re-wrenches.org

List-Archive: 
http://lists.re-wrenches.org/pipermail/re-wrenches-re-wrenches.org

List rules & etiquette:
www.re-wrenches.org/etiquette.htm <http://www.re-wrenches.org/etiquette.htm>

Check out participant bios:
www.members.re-wrenches.org <http://www.members.re-wrenches.org>

_______________________________________________ List sponsored by Home Power
magazine List Address: RE-wrenches at lists.re-wrenches.org Options & settings:
http://lists.re-wrenches.org/options.cgi/re-wrenches-re-wrenches.org
List-Archive: 
http://lists.re-wrenches.org/pipermail/re-wrenches-re-wrenches.org List
rules & etiquette: www.re-wrenches.org/etiquette.htm Check out participant
bios: www.members.re-wrenches.org

-------------- next part --------------
An HTML attachment was scrubbed...
URL: <http://lists.re-wrenches.org/pipermail/re-wrenches-re-wrenches.org/attachments/20120702/ef03123e/attachment-0004.html>

More information about the RE-wrenches mailing list