Roof deterioration and impact: A questionnaire survey


Roofing is one of the building components which is most subject to deterioration. Maintenance and renewal of roofs are, therefore, crucial and require frequent inspection and good understanding of roof deterioration with time. In an effort towards facilitating roof condition assessment and subsequent repair decisions, this article first discusses the previous studies related to roof inspection and deterioration, followed by a two-stage survey among roofing experts. The first stage elicits the most common defects, their contribution to failure, symptoms of poor and critical roofs, and impact of roof deterioration on other components.

Fourteen survey responses were obtained from the Toronto District School Board related to school buildings with low-slope built-up roofs. Based on the first-stage results, a pictorial database of roof pictures with different defects was created and initially ranked. The ranking of pictures was then confirmed through the second phase of the survey. The research provides a better understanding of roof deterioration and the developed pictorial database acts as a visual guidance system to facilitate fast and less subjective inspection of roofs, and ultimately to better asset management of building facilities.Also visit; Roofing survey.

Roofing is one of the main components of any building and is a relatively large investment (Suarez, 1999). Many studies (for example, NCES, 2003) have identified roofing as one of the most deterioration-prone building components. Therefore, being proactive with the health of a roofing system will ultimately reduce the building financial liability (Suarez, 2005).

The average life of roofs varies by the type and material of the roof (Lewis and Payant, 2000). However, the life expectancy for roofs, like any other building component, is greatly influenced by the presence or absence of a roof maintenance programme (Suarez, 1999). According to the National Roofing Contractors Association, roofs that are not properly maintained will last approximately half of their anticipated normal service life (Suarez, 1999).

Roof systems are generally divided into two categories: low slope and steep slope, as shown in Figure 1. Many studies (Cullen and Graham, 1996; Bailey and Bradford, 2005) have revealed that built-up roof (BUR) systems are the most common roof type in Canada. To facilitate an in-depth investigation of roof defects, this article focuses on BUR systems only. BUR systems have been in use in the United States for more than 100 years. They are generally composed of alternating layers of bitumen and reinforcing fabrics that create a finished membrane. The number of plies in a cross section is the number of plies on a roof. The reinforcing fabrics are also called roofing felts or ply sheets. Roofing felts are reinforced with either glass-fibre mats or organic mats. The bitumen typically used in BUR systems is asphalt, coal tar or cold-applied adhesive. Surfacing for BUR systems include aggregate (such as gravel, slag or mineral granules), glass-fibre or mineral surfaced cap sheets, hot asphalt mopped over the entire surface, aluminium coatings or elastomeric coatings.

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