In San Jose we have a similar policy, however, not as liberal. Our criteria
is that if the total weight of the roof, including the existing and new
materials is less than 10 psf, we would not ask for calcs. The rationale for
this is that most likely the original calculations would have assumed
minimum 10 psf dead load. With most reroofing involving clay or concrete
tiles the dead load will most likely exceed 10 psf and therefore would
trigger a structural analysis.
City of San Jose
From: Tom.Hunt(--nospam--at)fluordaniel.com [SMTP:Tom.Hunt(--nospam--at)fluordaniel.com]
Sent: Wednesday, April 14, 1999 8:35 AM
Our homeowners association is planning on reroofing our entire
of 165 buildings (4 to 5 units per building). They have
options down to 5 roof coverings all of which are class A
clay tile. The most likely choice will be "ClayMax" by US Tile
plywood sheeting. The existing 20+ year old roofs are cedar
on what looks like 1/2 inch by 6 inch planks spaced about 12
o/c (you can see 4 to 6 inch of the black paper between the
The new roof system is obviously heavier than the existing
therefore will generate more seismic load to the shear walls.
shocked to learn that the city of Irvine has a "city policy"
the clay tiles (EXCLLUDING the addition of plywood) are less
psf then NO structural calculations are required. The ClayMax
weight 5.8 psf.
The city official I talked to said that since the plywood would
"extra seismic rigidity" they discount the added weight of the
plywood. I politely explained that with the 3 to 4 psf added
roofs from the new tiles and plywood the shear walls will be
more seismic load regardless of the roof rigidity. His comment
that since the buildings are 20+ years old they would never
with the added weight and newer codes. Duh!!
For those with conventional construction and reroofing
am a concrete/steel guy) is it normal not to require structural
calculations when reroofing with a heavier system. Without
calculations I would think as a minimum this could void our
Every time we have a good shaker I get cracks around the door
and it seems this will only make it worse. Any other comments
I should also note that we are located on a slight hill and
is half slab on grade and half elevated. The elevated half is
feet above grade.