HomeMy WebLinkAbout2nd City Plan Correction - RESPONSE 082922.pdfDE Project #22-069
August 29, 2022
Raymond Tao, Building Official
City of Diamond Bar
Building and Safety Division
21810 Copley Drive
Diamond Bar, CA 91765
Re: Diamond Bar Village Condominiums – PLAN CHECK RESPONSE #2
23601 Golden Springs Drive
Diamond Bar, CA
Plan Check Corrections Response Letter:
Please see Du Mont Engineering’s responses below in green.
Du Mont Engineering received the following comment via email from Marshall Pihl:
I have now reviewed the finish details by DuMont Engineering. (I worked for OAC in Seattle,
Washington prior to joining Cannon and investigated dozens of buildings that had extensive wood
rot. OAC specializes in building envelope design). The DuMont detailing shown should generally
provide good shedding of rain. My only concern is the extent of the Bituthene wrap.
Bituthene materials have virtually zero permeability which is great for keeping water out. The
downside is that it also keeps water in. 20 years ago, building envelope designs included the use of
peel and stick materials (up to 12” wide) around windows to prevent driven rain from getting into
wall systems. Building envelope designers soon discovered that those systems often resulted in
vapor (escaping the living spaces) getting trapped behind those wraps leading to condensation and
wood rot. Reducing the widths of the wrap materials, using products with higher porosity rates, and
a higher attention to completeness of the vapor barrier (retarder) system on the inside face of the
wall can limit the risk. Bituthene on horizontal surfaces such as the top of the parapet walls will
provide long term protection. I have investigated roof systems where Blueskin was installed over an
entire roof area without venting that resulted extensive wood rot and complete replacement of the
roof system.
At the Dimond Bar Village, I recommend wrapping the bituthene down over the vertical wall
building wrap far enough to allow the cap flashing connectors to penetrate through as the
Re: Diamond Bar Village Condominiums – PLAN CHECK RESPONSE #2
23601 Golden Springs Drive
Diamond Bar, CA
Page 2 of 2
bituthene material seals around connectors. I recommend the “12” minimum” length of the
bitumen wraps indicated on the drawings be reviewed by the building envelope designer.
If you have any questions regarding these items, please do not hesitate to call or respond to this
email.
RESPONSE: Du Mont Engineering spoke with Marshall Pihl, and he noted that this
is not an official correction but a recommendation to review the bituthene warp length
and consider a shorter length. He pointed out that the design, as submitted, would work
as intended, but Marshall explained his experience with bituthene over the years as
listed above, and we met at a middle ground and adjusted the dimension to 6” rather
than the 12” specified initially.
o Please see the updates on sheets A-3.0, A-3.1, and A-4.0
If you have any questions or need further information regarding this response letter, please
contact this office.
DATED:_______08/29/22 ________ By:______________________________
Du Mont Engineering
Westin Gaudet, AIA
Architect
Architect License #C35358
DATED:_______08/29/22 ________ By:______________________________
Du Mont Engineering
Borna Bahrami, P.E.
Engineer
Civil Engineer License #C91510