Ask the Engineer: Diagnostic Probes Should Be Nothing Alien to Boards
March 6, 2014 — A reader asks: I sit on the co-op board of a six-story building in Inwood. We recently hired an engineer to design and administer the replacement of our roof system over a wooden deck, which over the years has suffered serious water damage and created persistent leaks. The engineer has requested several investigative probes, which will cost us an additional $4,500. I know that doesn't sound like a lot for a $350,000 project, but the co-op's finances are tight, so we're wondering if probes are really necessary. What exactly are these probes?
Think of your building as a patient and your engineer as its doctor. A doctor assesses a patient's health by visually examining his or her external parts: skin, limbs, eyes, ears, mouth, etc. But to get a fuller understanding of the patient's condition, the doctor sometimes needs to look "inside" the person using tools such as X-rays, MRIs, CAT scans, etc.
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Similarly, an engineer or architect can evaluate a building's systems by examining the visible systems and components: the façade, roofing membrane, parapets, boilers, pipes, etc. But some of a building's underlying conditions may not be visible — such as the deterioration of a roof deck or backup masonry — so investigative probes are often required to identify potential problems.
This entails carefully cutting an opening in a building element to access another building element for evaluation, such as a steel beam or column behind a wall or a roof deck underneath roofing membranes. With a more complete understanding of the situation at hand, the engineer or architect can develop a realistic scope of work, draft precise construction details and prepare an accurate specifications package for bidding. In this way, investigative probes help minimize surprises during construction and lessen the number and costs of change orders later in the project.
Identifying the Problem
Probes are identified during the design phase of the project, usually after the initial site work. Typically, probes are done in areas where the engineer or architect suspects a problem but cannot confirm it with visual observation. For example, a spongy part of the roof may indicate water damage underneath the membranes, and discoloration on a ceiling could mean a leak behind a wall. Other common areas for a probe include stucco coatings, which hide underlying construction; windows and doors, to determine if lintels are bolted or loosely laid; parapet walls, to confirm structural integrity; and building corners with long vertical cracks, to examine the structural steel.
After analyzing the building conditions and identifying the necessary probes, the engineer or architect prepares an RFP (request for proposal) for the work and solicits bids from contractors. The vendor chosen to conduct the probes is not necessarily the contractor that will perform the construction work on the project.
Investigative probes may seem like a bothersome extra step in a project, and bypassing them might appear an easy way to trim costs for co-op and condo boards on a tight budget. But they provide additional information about a building's condition and help minimize major surprises down the road. So they should be considered a cost-effective, due-diligence measure essential to any major repair program.
Stephen Varone, AIA, and Peter Varsalona, PE, are principals at Rand Engineering & Architecture.
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