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Engineer's Corner: The Usefulness of Probes to Identify Underlying Conditions

A comprehensive building envelope restoration project is usually a costly venture that addresses most or all of a building’s issues in an effort to restore the façades, roof, garage, etc. as close as possible to their original condition. Unfortunately, since these types of restoration projects are expensive and disruptive, they are likely to be put off until absolutely necessary, or required by law.

Probes to confirm existing conditions, and to identify possible underlying issues, should be performed during a building envelope restoration project. This is especially true if comprehensive repairs at a building have not been conducted for some time. If probes are not performed, these hidden conditions could arise at a later phase of the restoration project, ultimately adding time and expense to the project’s schedule and budget.

An example would be the steel structure buried within the building façade. Signs of steel deterioration that require further investigation are often evident. Rust colored stains on a façade, along with spalled, cracked or bulging masonry, are all clear indications that water might be contacting the structural steel. Probes should be performed to inspect the structural steel and determine the required repair and maintenance.

Water infiltration can cause structural failure

During our investigations, we often come across a number of poor drainage conditions and waterproofing details, especially at older buildings. A lack of weep vents or through wall flashing prevents infiltrating water from properly exiting the façade. Additionally, if a non-breathable (non-permeable) coating has been applied to the building in an attempt to prevent water infiltration, this problem is compounded. Over time, water will deteriorate steel, destroy structural connections, and could eventually cause a structural failure.

Similar to building facades, structural concrete decks in parking garages contain steel reinforcement. If the concrete is cracked or uncoated, water might be penetrating and causing the reinforcement to deteriorate. Rust colored stains and cracks at the parking deck surface, or at the underside of an elevated parking deck, are again signs that this is likely occurring. Probes throughout a parking deck would once again help determine the condition of this reinforcing steel.

Typically, flat roof systems are comprised of several components (i.e. deck, insulation, cover board and waterproofing). Water can get trapped within these components and damage the roof’s framing or insulation. Unforeseen insulation or structural issues could result from prolonged water infiltration at a flat roof that is not remedied in a timely manner. A soft or spongy roof deck surface is an apparent sign of infiltrating water issues; however, probes of the existing roof system will offer a clearer indication of the condition of the framing and insulation below.

While probes add some time and cost to restoration projects, they allow the designer to anticipate repair, replacement and maintenance of existing reinforcement, which in turn, enables them to provide a more realistic design and budget.

Article by Joe Czaszynski, Sullivan Engineering, LLC

Photo:Probes to confirm existing conditions, and to identify possible underlying issues, should be performed during a building envelope restoration project.

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