26 September 2006
CHAPTER 5 RE-ROOFING REQUIREMENTS
Eventually every roofing system will reach the end of its economic life. Reroofing
options include removal and replacement, re-cover (where a new system is
superimposed over an existing system), and partial replacement. Reasons to re-
cover include reduced first costs and reduced impact on the building occupants.
Do not re-cover over wet or deteriorated materials.
Re-roofing can be considered a problem or an opportunity. Re-roofing can be a
problem since the work is typically performed while the structure is occupied.
Often there are concerns with noise, fumes, access, and interruption of building
use. Re-roofing can be an opportunity since there is no better time to upgrade
the roof system than while re-roofing. Changes in the roof system may be
mandated by revisions to ASCE 7 or by needed improvement in drainage or
thermal performance. It can be an opportunity to elevate or redesign problem
roof elements; to install deck supported curbs that are flashed independently of
the wall (resolving persistent flashing problems due to differential movement),
and to resolve condensation problems or thermal insulation deficiencies.
Re-roofing decisions begin with a survey of existing conditions. This may include
visual inspection, infrared moisture surveys, and roof cut analysis. Structural
analysis may also be required, especially if a different type of roof is
contemplated which affects dead load, drainage, or seismic behavior. One
method of analyzing the condition of an existing roof is to use the ROOFER
Engineered Management System (EMS). The ROOFER EMS is a decision-
making tool to help manage an installation's low-slope membrane and asphalt
shingle roofing assets. It includes procedures for collecting inventory and
inspection information, evaluating roof conditions, identifying repair/replacement
strategies, prioritizing projects, and developing work plans. Micro ROOFER, a
microcomputer application, provides data storage and analysis and generates
The NRCA Manual provides typically allowable re-roofs over existing roofing.
See below for other considerations.
Low Sloped Versus Steep-Sloped Considerations.
The low slope and steep sloped roof present different challenges in re-roofing.
An attic space, typically found in steep slope roof construction, provides
separation of construction activities from the interior of the building. However on
steeper slope roofs, scaffolding and protected access to the building may be
major construction cost items.