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Hanna Andersson Building – Multi-Phase Roof Replacement







Quality Assurance



Mapleton Investments

Colliers International

Roof replacement design, construction administration, quality assurance inspections


This project originated from a roof evaluation conducted by PRC in 2016, followed by a roof repair project designed by PRC later that year, and comprises the first two phases of a planned three phase roof replacement. Formerly known as the Jantzen Park building, the Hanna Andersson building (The Hanna) was originally constructed in three major periods between 1929 and 1945 from designs by Architect Richard Sundeleaf for the Jantzen Knitting Mills Company. In 1991 the building was recorded on the National Registry of Historic Places and designated as a Landmark for its significance in Portland’s history, with its unique saw-tooth and barrel roof forms identified in the listing.


For the first phase of replacement, at the southeast quadrant of the building, PRC was tasked to design a system that could be installed with little to no disruption of the sensitive operations taking place in the creative workspace below. To address this concern, PRC designed a recover roof system that allowed the existing asphalt built-up membrane remain in place, thereby minimizing noise and the mess associated with full system removal and disposal, while also keeping the installation schedule as short as possible. Complete tear-off and replacement was necessary for the second phase at the north half of the building given that these areas were already covered by two successive roof systems – the maximum allowable by code. During both phases, PRC’s design addressed numerous high-maintenance conditions, improved drainage, and reconfigured the existing chaotic tangles of service utilities to create a more organized service environment.


Through careful design and attentive oversight during construction, PRC helped deliver a successful roof replacement with an elevated standard of quality. The resulting installation is clean, orderly, and expected to provide high-performance low-maintenance service for decades to come. Phase three is expected to be undertaken within the next couple of years.

Hanna Andersson Building – Multi-Phase Roof Replacement
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