The Los Angeles Central Library was built in 1926 and extensively renovated in 1988 -1993 after an arson fire. In 2001 the building was renamed the Richard Riordan Central Library in honor the former Los Angeles mayor.
The library is surrounded by hi-rise buildings and the decision was made to surface the roof with a tan colored single ply PVC membrane as opposed to the more effective white membrane in consideration of the neighboring properties. The system selected will, in addition to having a 20 year leak-free warranty, enable a green roof or solar PV to be added later as funds permit.
The roofing project required removal of 400 tons of existing ballast rock covering an aging EPDM membrane, then removal of the EPDM membrane. The existing 2” thick XPS insulation under the EPDM membrane was determined to be in good condition and was left in position. The library takes up an entire city block located in the heart of downtown Los Angeles and as such access to the building is extremely limited. Simply staging the vacuum trucks to remove the ballast rock and the crane to remove the existing paver blocks and load new roof materials was a major project requiring rolling street closures as the work progressed.
The reroofing process began with the installation of ½’ thick DensDeck mechanically fastened through the existing insulation into the concrete deck. The tan 60 mil single ply felt back PVC membrane was then fully adhered to the DensDeck. Green walkpads were added to protect the areas that are frequently serviced. The membrane installed complies with California Code Title 24 Part 6. A major benefit of this installation is the 20 year warranty on the watertight roof. As no additional insulation was added, there were minimal energy gains for this system but the Title 24 membrane and Densdeck combine to provide a calculated energy saving of 4 cents per square foot per year which equates to $32,000 annually.