<html>
<head>
<meta http-equiv="content-type" content="text/html; charset=ISO-8859-1">
</head>
<body text="#000000" bgcolor="#FFFFFF">
A local jurisdiction is starting to require that we document
non-truss rafter dimensions, span and attachment points. This seems
to be a fad that other jurisdictions have required at times, and
other times not. When the existing structure was deemed
insufficient, we've either paid a structural engineer to do some
calcs and recommend more attachment points, or sistered the rafters
to match the spacing given in the 20 psf table in the UBC.<br>
<br>
Would the dead load from the PV modules ever be more than that from
adding a second layer of comp roofing, which does not require a
structural analysis? Would the live point loads from the PV system
ever be greater than the point load of a person walking on the
roof? If the answers are "no" and "no", then it seems that a roof
that supports a person walking on it would not be adversely affected
by the installation of a non-ballasted residential PV system.<br>
<br>
I looking for help with the following:<br>
<blockquote>1. Has there been an occasion when a residential PV
system (non-ballasted), that was installed per the manufacturer's
instructions, detached from a roof or caused damage to the
structure of the roof?<br>
2. Is there a good explanation for why structural review for
residential PV systems is necessary?<br>
3. Are there studies or resources that I can present to building
officials to explain why structural review for residential PV
systems is not necessary?<br>
</blockquote>
Thanks for your help.<br>
<br>
Bruce<br>
<br>
</body>
</html>