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<p>I would add to this that the size of the lag is a factor too.
3/8" lags into 1-1/2" wide rafters are going to cause much more
damage, and leave larger voids, than the new 1/4" high strength
lags I use now. I like the rafter sistering idea, as a solution,
as well as moving the rails up or down several inches to get away
from the previous hole. A third idea is staggering the mount
pattern from rail to rail, which is something we should all be
doing anyway to insure the loads are more equally distributed
across all the rafters. Then we just change the pattern on the 2nd
installation.</p>
<p>Unfortunately I think much of this will be lost, since some of
the companies that roofers subcontract with to do these remove and
replace jobs are not always the top solar contractors. <br>
</p>
<p>Ray Walters<br>
Remote Solar<br>
</p>
<div class="moz-cite-prefix">On 5/29/2024 10:17 PM, William Miller
via RE-wrenches wrote:<br>
</div>
<blockquote type="cite"
cite="mid:7ab3de77e7c5b136bffda84c79357d06@mail.gmail.com">
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<p class="MsoNormal"><span
style="font-size:12.0pt;font-family:"Verdana","sans-serif";color:#1f497d">Scot:</span></p>
<p class="MsoNormal"><span
style="font-size:12.0pt;font-family:"Verdana","sans-serif";color:#1f497d"> </span></p>
<p class="MsoNormal"><span
style="font-size:12.0pt;font-family:"Verdana","sans-serif";color:#1f497d">Fascinating
question. It’s a bit ironic that the changing climate is
damaging the equipment we are utilizing to combat climate
change.</span></p>
<p class="MsoNormal"><span
style="font-size:12.0pt;font-family:"Verdana","sans-serif";color:#1f497d"> </span></p>
<p class="MsoNormal"><span
style="font-size:12.0pt;font-family:"Verdana","sans-serif";color:#1f497d">A
lag unscrewed will damage a wooden member less than a lag
ripped out. From your post it seems we are dealing with the
former, rather than the latter.</span></p>
<p class="MsoNormal"><span
style="font-size:12.0pt;font-family:"Verdana","sans-serif";color:#1f497d"> </span></p>
<p class="MsoNormal"><span
style="font-size:12.0pt;font-family:"Verdana","sans-serif";color:#1f497d">If
your layout isn’t changing there is a likelihood that the
new mounting locations will be at our near the old mounting
locations. This will be true for a rafter lag or deck mount
screw. It seems to me the process of re-screwing in the
same spot in a rafter is just as questionable as re-screwing
in the same spot in sheeting. I see no benefit in deck
mounting and many disadvantages. </span></p>
<p class="MsoNormal"><span
style="font-size:12.0pt;font-family:"Verdana","sans-serif";color:#1f497d"> </span></p>
<p class="MsoNormal"><span
style="font-size:12.0pt;font-family:"Verdana","sans-serif";color:#1f497d">If
severe weather is an issue I would avoid deck mounting
unless you have vetted the decking and the applicability of
the chosen fasteners to that material. I would not
standing-seam mount without knowing how the sheeting panels
are secured and finding a method to calculate how many clips
are needed given the increasing wind loads.</span></p>
<p class="MsoNormal"><span
style="font-size:12.0pt;font-family:"Verdana","sans-serif";color:#1f497d"> </span></p>
<p class="MsoNormal"><span
style="font-size:12.0pt;font-family:"Verdana","sans-serif";color:#1f497d">I
see two questions about reinstalling screws repeatedly:</span></p>
<p class="MsoListParagraph"
style="text-indent:-.25in;mso-list:l0 level1 lfo2"><span
style="font-size:12.0pt;font-family:"Verdana","sans-serif";color:#1f497d"><span
style="mso-list:Ignore">1.<span
style="font:7.0pt "Times New Roman""> </span></span></span><span
style="font-size:12.0pt;font-family:"Verdana","sans-serif";color:#1f497d">Is
the rafter less able to support loads? Or,</span></p>
<p class="MsoListParagraph"
style="text-indent:-.25in;mso-list:l0 level1 lfo2"><span
style="font-size:12.0pt;font-family:"Verdana","sans-serif";color:#1f497d"><span
style="mso-list:Ignore">2.<span
style="font:7.0pt "Times New Roman""> </span></span></span><span
style="font-size:12.0pt;font-family:"Verdana","sans-serif";color:#1f497d">Is
the rafter (or decking) less able to retain the fasteners
holding the PV to the roof?</span></p>
<p class="MsoNormal"><span
style="font-size:12.0pt;font-family:"Verdana","sans-serif";color:#1f497d"> </span></p>
<p class="MsoNormal"><span
style="font-size:12.0pt;font-family:"Verdana","sans-serif";color:#1f497d">Speculation
on the above:</span></p>
<p class="MsoListParagraph"
style="text-indent:-.25in;mso-list:l2 level1 lfo3"><span
style="font-size:12.0pt;font-family:"Verdana","sans-serif";color:#1f497d"><span
style="mso-list:Ignore">1.<span
style="font:7.0pt "Times New Roman""> </span></span></span><span
style="font-size:12.0pt;font-family:"Verdana","sans-serif";color:#1f497d">Wood
fibers adhere to each other. They are not like a bundle of
straws. If you damage a fiber in one place, it is supported
on either side of the point of damage by this adherence. My
guess is by just withdrawing screws a few times you do not
compromise the load handling ability of a rafter member.
Site built rafters require different considerations than
trusses. Site built are a wild-card and need to be
considered on a case-by-case basis.</span></p>
<p class="MsoListParagraph"
style="text-indent:-.25in;mso-list:l2 level1 lfo3"><span
style="font-size:12.0pt;font-family:"Verdana","sans-serif";color:#1f497d"><span
style="mso-list:Ignore">2.<span
style="font:7.0pt "Times New Roman""> </span></span></span><span
style="font-size:12.0pt;font-family:"Verdana","sans-serif";color:#1f497d">If
you penetrate wood with screws multiple times in a small
area, you are going to make that area “soft.” Screw holding
capabilities will be drastically reduced.</span></p>
<p class="MsoNormal"><span
style="font-size:12.0pt;font-family:"Verdana","sans-serif";color:#1f497d"> </span></p>
<p class="MsoNormal"><span
style="font-size:12.0pt;font-family:"Verdana","sans-serif";color:#1f497d">Options
that I see:</span></p>
<p class="MsoNormal"><span
style="font-size:12.0pt;font-family:"Verdana","sans-serif";color:#1f497d"> </span></p>
<p class="MsoListParagraph"
style="text-indent:-.25in;mso-list:l1 level1 lfo1"><span
style="font-size:12.0pt;font-family:"Verdana","sans-serif";color:#1f497d"><span
style="mso-list:Ignore">1.<span
style="font:7.0pt "Times New Roman""> </span></span></span><span
style="font-size:12.0pt;font-family:"Verdana","sans-serif";color:#1f497d">Flashed
stanchions. The lags never need to be removed.</span></p>
<p class="MsoListParagraph"
style="text-indent:-.25in;mso-list:l1 level1 lfo1"><span
style="font-size:12.0pt;font-family:"Verdana","sans-serif";color:#1f497d"><span
style="mso-list:Ignore">2.<span
style="font:7.0pt "Times New Roman""> </span></span></span><span
style="font-size:12.0pt;font-family:"Verdana","sans-serif";color:#1f497d">Blocking,
to attach in new locations.</span></p>
<p class="MsoListParagraph"
style="text-indent:-.25in;mso-list:l1 level1 lfo1"><span
style="font-size:12.0pt;font-family:"Verdana","sans-serif";color:#1f497d"><span
style="mso-list:Ignore">3.<span
style="font:7.0pt "Times New Roman""> </span></span></span><span
style="font-size:12.0pt;font-family:"Verdana","sans-serif";color:#1f497d">Sistering,
again to attach in new locations.</span></p>
<p class="MsoListParagraph"
style="text-indent:-.25in;mso-list:l1 level1 lfo1"><span
style="font-size:12.0pt;font-family:"Verdana","sans-serif";color:#1f497d"><span
style="mso-list:Ignore">4.<span
style="font:7.0pt "Times New Roman""> </span></span></span><span
style="font-size:12.0pt;font-family:"Verdana","sans-serif";color:#1f497d">Not
deck mounting (IMHO).</span></p>
<p class="MsoNormal"><span
style="font-size:12.0pt;font-family:"Verdana","sans-serif";color:#1f497d"> </span></p>
<p class="MsoNormal"><span
style="font-size:12.0pt;font-family:"Verdana","sans-serif";color:#1f497d">Anecdote:
We had a tile roof mount inspected one August afternoon.
The inspector insisted on looking in the attic. We asked
why and he said this city has a particular concern about
structural integrity of wood framed roofs. I was aware of
this because I have had some silly arguments about this with
the lead inspector. Apparently they have seen a lot of
big-box solar company installers drive lags carelessly and
had the lags blow out the side of the rafter. If they spot
this they make the installer hire an engineer and design a
system to sister the rafters to engineering standards. I
totally get this concern. We use a rafter locator and are
really careful. This is not to say we have not had a blow
out now and then. You gotta have a feel for the torque
resistance of a lag while seating.</span></p>
<p class="MsoNormal"><span
style="font-size:12.0pt;font-family:"Verdana","sans-serif";color:#1f497d"> </span></p>
<p class="MsoNormal"><span
style="font-size:12.0pt;font-family:"Verdana","sans-serif";color:#1f497d">Thank
you for bringing this up. As I said, fascinating (to this
wonk).</span></p>
<p class="MsoNormal"><span
style="font-size:12.0pt;font-family:"Verdana","sans-serif";color:#1f497d"> </span></p>
<p class="MsoNormal"><span
style="font-size:12.0pt;font-family:"Verdana","sans-serif";color:#1f497d">William</span></p>
<p class="MsoNormal"><span
style="font-size:12.0pt;font-family:"Verdana","sans-serif";color:#1f497d"> </span></p>
<div>
<p class="MsoNormal"><span
style="font-size:12.0pt;font-family:"Arial","sans-serif";color:#1f497d">Miller
Solar</span></p>
<p class="MsoNormal"><span
style="font-size:12.0pt;font-family:"Arial","sans-serif";color:#1f497d">17395
Oak Road, Atascadero, CA 93422</span></p>
<p class="MsoNormal"><span
style="font-size:12.0pt;font-family:"Arial","sans-serif";color:#1f497d">805-438-5600</span></p>
<p class="MsoNormal"><span
style="font-size:12.0pt;font-family:"Arial","sans-serif";color:#1f497d"><a
href="http://www.millersolar.com/"
moz-do-not-send="true"><span style="color:blue">www.millersolar.com</span></a></span></p>
<p class="MsoNormal"><span
style="font-size:12.0pt;font-family:"Arial","sans-serif";color:#1f497d">CA
Lic. 773985</span></p>
<p class="MsoNormal"><span style="color:#1f497d"> </span></p>
</div>
<p class="MsoNormal"><span
style="font-size:12.0pt;font-family:"Verdana","sans-serif";color:#1f497d"> </span></p>
<div>
<div
style="border:none;border-top:solid #b5c4df 1.0pt;padding:3.0pt 0in 0in 0in">
<p class="MsoNormal"><b><span
style="font-size:10.0pt;font-family:"Tahoma","sans-serif"">From:</span></b><span
style="font-size:10.0pt;font-family:"Tahoma","sans-serif"">
RE-wrenches [mailto:<a
href="mailto:re-wrenches-bounces@lists.re-wrenches.org"
moz-do-not-send="true" class="moz-txt-link-freetext">re-wrenches-bounces@lists.re-wrenches.org</a>]
<b>On Behalf Of </b>Scot Arey via RE-wrenches<br>
<b>Sent:</b> Wednesday, May 29, 2024 3:16 PM<br>
<b>To:</b> 'RE-wrenches'<br>
<b>Cc:</b> <a href="mailto:scot.arey@solarcentex.com"
moz-do-not-send="true" class="moz-txt-link-freetext">scot.arey@solarcentex.com</a><br>
<b>Subject:</b> [RE-wrenches] How many times can a
rafter have a lag screw put in and out before it is no
longer structurally sound? Some roofs getting their 3rd
set of new shingles</span></p>
</div>
</div>
<p class="MsoNormal"> </p>
<p class="MsoNormal">With all our Texas hail storms, we now have
roof solar systems that might have to come down for the third
time as hail-pockmarked shingles need replacement. We’re at
the 11-year mark of doing business and we have some customers
ready for another insurance roof claim,</p>
<p class="MsoNormal"> </p>
<p class="MsoNormal">So that means a new set of lag screws
drilled into rafters…after how many times is that 2x6 rafter
not 2x6 strength?<br>
<br>
I’ve asked this to my 3<sup>rd</sup> party structural engineer
and instead of an answer got a “wow, hadn’t thought of that.”
We’ve considered going to deck mounts to avoid rafters at the
3<sup>rd</sup> “detach and reset.”<br>
<br>
Any of you guys consider this and have your techniques? I
suppose in perfect world, the mount would stay in place and
roofer would shingle around it but we still use old-school
metal flashing so that is really not possible. I look forward
to hearing your thoughts on this.</p>
<p class="MsoNormal"> </p>
<p class="MsoNormal"><img id="Picture_x0020_1"
src="cid:part1.y0mZ38M7.hAjBoLDY@solarray.com" class=""
width="385" height="152" border="0"><span
style="mso-ligatures:none"></span></p>
<p class="MsoNormal"> </p>
</div>
<br>
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