<div dir="ltr"><div class="gmail_default" style="font-family:verdana,sans-serif">I'd hate to speak for the engineers, but usually they do a CYA by saying that the contractor is responsible for assessing whether the structure is adequate, which usually is a satisfactory exclusion accepted by AHJs. Of course that shifts the risk to the contractor.</div>
<div class="gmail_default" style="font-family:verdana,sans-serif"><br></div><div class="gmail_default" style="font-family:verdana,sans-serif">>From a practical standpoint, you can say the same thing about the truss to header attachment or even the header to wall attachment (especially if not concrete). The truth of the matter is that when a devastating storm hits, all that's left are sticks (<a href="http://www.boston.com/bigpicture/2010/08/remembering_katrina_five_years.html">http://www.boston.com/bigpicture/2010/08/remembering_katrina_five_years.html</a>). Local anecdotal evidence from Hurricane Charley suggests that solar panels (mostly solar pool heating) had no impact on whether a roof stays on or not. We saw panels ripped off and we saw completely intact roofs knocked off with panels still attached. I wish we had more pictures, but it was pretty chaotic and that was the last thing on our minds.</div>
<div class="gmail_default" style="font-family:verdana,sans-serif"><br></div><div class="gmail_default" style="font-family:verdana,sans-serif">Given that we make all kinds of other assumptions about existing structures and systems anyway, I am pretty comfortable with the risk/reward tradeoff with a sheathing-only attachment method as long as we have a reasonable analysis from an engineer.</div>
<div class="gmail_default" style="font-family:verdana,sans-serif"><br></div><div class="gmail_default" style="font-family:verdana,sans-serif">Jason</div><div class="gmail_default" style="font-family:verdana,sans-serif"><br>
</div><div class="gmail_default" style="font-family:verdana,sans-serif"><br></div><div class="gmail_extra"><br><div class="gmail_quote">On Tue, Jun 3, 2014 at 12:21 PM, Andrew Truitt <span dir="ltr"><<a href="mailto:atruitt@gmail.com" target="_blank">atruitt@gmail.com</a>></span> wrote:<br>
<blockquote class="gmail_quote" style="margin:0px 0px 0px 0.8ex;border-left-width:1px;border-left-color:rgb(204,204,204);border-left-style:solid;padding-left:1ex"><div dir="ltr"><div><br>All - There have been many products over the years that were engineered to fasten to roof sheathing only (remember BP Integra and SunPower SmartMount?), and I can certainly buy that their engineered uplift ratings are legit in terms of the strength of the connection between the sheathing and the racking system, but my concern is about the strength of the connection between the sheathing and the roof framing system. Similar to using S-5!'s clips, I don't see how we can really trust those footings without knowing the details (e.g. fastener number and type) of the roof / rafter connection, and those details can be very tough to access for built structures.</div>
<div class="gmail_extra"><div dir="ltr"><div dir="ltr"><div dir="ltr"><div dir="ltr"><div dir="ltr"><br></div><div dir="ltr">I think this has been discussed on this list previously, but I would be very curious to hear if there have been any new developments in how designers approach this issue. </div>
<div dir="ltr"><br></div><div dir="ltr">Jason - How do you're engineers handle this challenge in those hurricane wind zones in Florida, where roofs can fly off even without having a bunch of sails mounted to them?</div>
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<br><br><div class="gmail_quote">On Tue, Jun 3, 2014 at 8:40 AM, Max Balchowsky <span dir="ltr"><<a href="mailto:max@seesolar.com" target="_blank">max@seesolar.com</a>></span> wrote:<br><blockquote class="gmail_quote" style="margin:0px 0px 0px 0.8ex;border-left-width:1px;border-left-color:rgb(204,204,204);border-left-style:solid;padding-left:1ex">
<div><div style="color:rgb(0,0,0);font-family:arial,helvetica,sans-serif;font-size:10pt;background-color:rgb(255,255,255)"><div><span>That does look like the early Unirac system, (I don't think they rated it for 140 mph). It wasn't designed to "hit" rafters, that's why there six screws in each base plate….</span></div>
<div></div><div> </div><div><span style="font-family:tahoma,'new york',times,serif">Max Balchowsky</span><br style="font-family:tahoma,'new york',times,serif"><span style="font-family:tahoma,'new york',times,serif">Design Engineer</span><br style="font-family:tahoma,'new york',times,serif">
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<div style="font-family:'times new roman','new york',times,serif;font-size:12pt"> <div dir="ltr"> <hr size="1"> <font face="Arial"> <b><span style="font-weight:bold">From:</span></b> Dave Click <<a href="mailto:daveclick@fsec.ucf.edu" target="_blank">daveclick@fsec.ucf.edu</a>><br>
<b><span style="font-weight:bold">To:</span></b> RE-wrenches
<<a href="mailto:re-wrenches@lists.re-wrenches.org" target="_blank">re-wrenches@lists.re-wrenches.org</a>> <br> <b><span style="font-weight:bold">Sent:</span></b> Tuesday, June 3, 2014 6:06 AM<br> <b><span style="font-weight:bold">Subject:</span></b> [RE-wrenches] Racking System - Identification Help<br>
</font> </div> <div><div><div><br>Hi all,<br><br>Anyone know what this racking system is? The permit drawings say Unirac <br>with lag screws and Eco-Fasten flashings, which this pretty clearly <br>isn't. I'd never seen this before, and I imagine this wind resistance is <br>
not quite the 140 mph that the installer claims it is. Of the ~250 wood <br>screws holding this system down into the roof, I think six of them <br>accidentally hit rafters.<br><br>Thanks!<br>Dave<br></div></div></div></div>
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