Preserving Structural Integrity

• By Brian D. Wentz
• 07/01/19

PHOTO © KEAST & HOOD

Is deferred maintenance—the practice of delaying building repairs—quietly wreaking havoc on your campus structures? A building’s structural system exhibits particular sensitivity to issues such as water infiltration, façade deterioration, corrosion, and decay. Whether for schedule or budget reasons, deferring seemingly minor maintenance or repair projects over time can cause major concerns during building renovations. When structural maintenance is postponed, repairs become more extensive, expensive, and intrusive. Addressing and correcting outstanding issues prior to renovation will ensure capital budgets, project schedules, and architectural objectives can be met.

According to the Sightlines 2018 State of Facilities in Higher Education report, which verified data from 360 colleges and universities across North America, annual stewardship funds increased 50 percent from 2007 to 2017, demonstrating a long-term commitment to building renovations. With most campus buildings constructed between 1950-1975 and from 2000-present, capital investment demands will soon be at an all-time high for both groups. JLL Research puts deferred maintenance estimates at $100 per square foot. With approximately six billion square feet of buildings, the $600 billion deferred maintenance price tag looms large.

Common Conditions

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The most common deferred maintenance issues affecting building structures include veneer failure, masonry deterioration, steel corrosion, and timber decay. Veneer failures may be evidenced by masonry spalling, when pieces break or flake off a building’s exterior finish, and typically affect concrete, terra cotta, and stone; corroded steel framing, often hidden by surface materials, may be indicated by spalling concrete encasement or by cracks or bulges around lintels or arches; or wood crushing, checking, and cracking may be a sign of timber decay.

The ongoing deferment of normal building maintenance related to these issues will typically result in more extensive repairs that cost more than the cumulative maintenance sums. A deteriorated façade, for example, may result in the continuous cleaning of interior finishes due to leaks, could necessitate installation of exterior safety precautions such as netting or barriers, and could ultimately affect the underlying building structure, requiring costly investigative work and supplemental shoring.

Before your renovation budget and schedule take unexpected hits, consider some common scenarios.

Scenario 1: Veneer Failure

If a piece of terra cotta falls on the campus and no one is around to hear it, does it sound an alarm?

PHOTO © KEAST & HOOD

It should. Beyond the immediate safety concern of veneer failures—that falling pieces could cause property damage or personal injury—these often signal more alarming structural concerns.

On a recent project, Keast & Hood structural engineers of Philadelphia, PA, performed a façade and cornice assessment after a small section of terra cotta cornice fell to the sidewalk eight stories below. Prior to completing the assessment, safety netting was installed from the cornice base up and over the parapet to prevent future pieces from falling. The condition assessment revealed large cracks in the terra cotta cornice caused by corrosion of the steel armature framing within the supporting wall. The steel corrosion resulted from air and moisture infiltration, which over time caused rust jacking. Rust jacking happens when the metal in iron and steel products corrodes and builds up a layer of iron oxide, or rust. The buildup of rust applies an outward force, causing cracks and displacements of building elements.

In this example, ongoing maintenance could have ensured face and head joints were in good condition, sealants and flashings were properly applied, and the proper shedding of water was taking place in order to prevent the deterioration of steel and terra cotta. A short period of deferred maintenance may have limited the problem to small sections that could be repaired. Instead, the condition assessment determined an extensive problem. Not only had rust jacking occurred in the cornice, but water had also infiltrated the top floor window heads, compromising the structure around the windows and requiring additional repairs and window replacement.

Scenario 2: Masonry Repointing

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Could deferred masonry repointing— repairing weathered or decayed exterior mortar joints—be more than skin deep?

Mortar joints naturally deteriorate over time. Regular maintenance to correct voids or cracks in the mortar joints has deeper implications than restoring the aesthetic beauty of a façade. Repointing also preserves the physical integrity of the masonry and prevents future damage.

Left untreated, deteriorated mortar joints allow water to infiltrate the façade. Continued exposure can lead to destruction of the mortar on the interior of the masonry wall, creating voids within the wall cavity. Both are difficult to detect or access.

During a renovation, repointing the façade may be a priority. In a well-maintained building, masons may detect small voids. These can be filled with additional masonry and properly repointed. In a building with deferred maintenance, mortar joint deterioration could lead to larger voids or more extensive damage. Where masons encounter large voids, ground-penetrating radar (GPR) or other techniques to survey the wall may be needed to determine if there are larger structural deficiencies. The presence of extensive voids may require the dismantlement and reconstruction of the entire masonry wall section.

Scenario 3: Wood Decay

Could a crack be a sign of wood decay?

While wood checking or cracking most often results naturally as part of the drying process, larger cracks or those in areas susceptible to water infiltration or insect infestation are cause for concern. Decayed wood members at the bottom of a wall stud or along a sill plate may be found during a renovation. For non-structural decayed members, epoxy consolidation is a technique that infuses epoxy into a void within a wood member, rendering it sound once again. In cases where timber decay or damage proves more significant, reinforcement or replacement would be necessary.

Scenario 4: Steel Corrosion

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Could the steel structure be corroding behind the walls?

Long-term corrosion not only causes rust jacking but also diminishes the load capacity and strength of structural steel framing. Glimpses of corrosion may appear as cracks above the corners of a doorway lintel, a bulge in a steel-supported masonry arch, or spalling of a concrete-encased steel beam. These tell-tale signs should prompt further investigation.

During renovation, it becomes particularly important to ensure a building’s structure maintains its strength and supports the new use. Minor surface corrosion can be removed by wire brush cleaning and protected by applying a rust-inhibiting coating. Extensive corrosion could require the addition of supplemental steel members to reinforce the corroded element. In a worst-case scenario, the structural member would need to be completely replaced. Deferring maintenance of seemingly minor cracks or bulges could impact the overall structure, with the potential for a catastrophic steel framing failure.

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Be Proactive

Early coordination among a campus facilities team, structural engineer, and architect can identify issues proactively, saving time and money and ensuring architectural and campus objectives can be met. JLL Research suggests regular facilities capital assessments to give engineers an opportunity to investigate campus building conditions and prioritize maintenance and repair needs.

If deferred maintenance issues may be a concern, seek professional guidance to ensure your building’s structural integrity may not compromise your renovation plans.

This article originally appeared in the College Planning & Management July/August 2019 issue of Spaces4Learning.