Diagnostic Technology: Looking for Trouble
Part 1: How to Identify Deficiencies in the Building Envelope
How to Identify Deficiencies in the Building Envelope
By Steve Bentz, Paul Swanson and Sara Guerrero - June 2011 - Windows & Exterior Walls
How long should a building facade last? How often should technicians have to make facade repairs? Maintenance and engineering managers must answer these questions, among many others, to ensure the safety and proper appearance of facilities. Complicating the matter is the fact that facade materials, such as steel, concrete, masonry, and glass, must perform for decades in harsh conditions.
Typical unsightly symptoms of structural movement, such as cracks, or indications of deterioration and weathering, such as spalls and corrosion, eventually worsen, prompting managers to schedule a facade assessment. Now, an emerging technology is giving managers a new and possibly more effective tool for finding problems and addressing them before they become larger and more costly.
A traditional facade assessment is a visual process performed up close using staging or vantage points on rooftop levels or from afar using binoculars and other visual aids. The process identifies visually evident distress, such as cracks, spalls, or significantly misaligned elements — movement that already has occurred to a degree that can be seen. But even experienced engineers cannot detect hidden signs of stress and deterioration.
As a result, the assessment represents a snapshot managers must extrapolate over an entire building. This approach is not very desirable when diagnosing problems and forecasting the cost to repair them. Visual assessments have been the primary — and least costly — method managers have used to determine the amount they must budget for immediate repairs versus repairs they can defer. The process also can be expensive, requiring hands-on, up-close evaluation from scaffolding or staging. The periods between assessments also can be years, and technicians only can perform them over a relatively small area of the facade, which limits their accuracy.
Visual assessments also are inherently subjective. Building envelopes manifest different signs of structural failure in varying and often unexpected ways. Depending on access to or the size and sheer number of structural systems in a building envelope, an engineer might not be able to observe or accurately quantify the severity of all existing defects.