Case History: How Forensic Engineering Reduced the Scope & Cost of a Coastal Concrete Restoration

A coastal Florida condominium association faced the possibility of an extensive and costly structural restoration after its two 18-story residential towers were classified as unsafe.

The three-wing towers had a distinctive configuration that exposed the structures to complex hurricane wind forces. Following a major wind event, cracking observed throughout portions of the buildings raised concerns that wind-induced movement and torsional response had accelerated structural deterioration.

The condominium’s original design professional evaluated the cracking and concluded that the buildings were unsafe. Based on that engineering determination, local county authorities classified the property accordingly.

Coastal residential towers subjected to marine environments and hurricane-force wind loading.

The consequences for the condominium association were substantial. If the visible cracking were assumed to represent widespread structural deterioration, the resulting repair program could require extensive demolition and reconstruction.

RAS Engineering was subsequently retained as Engineer of Record to independently evaluate the condition of the structures and answer a fundamental question:

Rather than extrapolating the extent of deterioration from visual cracking alone, RAS developed a systematic forensic testing protocol. Multiple forms of field and material evidence were correlated to distinguish observed distress from conditions actually requiring structural repair.

The investigation demonstrated that the buildings could be repaired without the major reconstruction initially anticipated. The case illustrates an important principle for condominium boards facing multimillion-dollar decisions:

The cost of determining what actually needs repair can be substantially less than the cost of repairing everything that might be damaged.

The Challenge: Visible Cracking & An Unsafe Determination

The property consisted of two 18-story coastal condominium towers, each incorporating three projecting wings. The geometry created a complex structural configuration under hurricane loading. Wind acting on the different wings could produce not only lateral movement but also torsional response—effectively twisting the structure under extreme wind conditions.

Following hurricane exposure, cracking observed in wall systems raised concerns that this movement had accelerated deterioration. The original engineering assessment interpreted the observed cracking as evidence of a potentially widespread structural problem and concluded that the building was unsafe, leading county building officials to classify the property accordingly.

For the condominium board, the engineering problem quickly became a financial problem. If deterioration was assumed to extend throughout large areas of the towers, the association could face a major restoration program involving extensive demolition, concrete repair, wall reconstruction, finishes, access systems, and related construction. Before committing the association to that level of expenditure, the actual extent and significance of the damage needed to be established.

The Problem With Designing Repairs From Visual Evidence Alone

Cracks are evidence that something occurred within a building, but a crack by itself does not necessarily establish:

• The underlying cause
• The depth of deterioration
• The condition of concealed materials
• Whether reinforcing steel is actively corroding
• Whether deterioration is localized or widespread
• Whether the condition affects structural capacity
• How much material actually requires removal and replacement

For coastal buildings, concrete and masonry systems are exposed simultaneously to wind, rain, salt, moisture, thermal movement, aging, corrosion, and previous repairs. Several mechanisms can therefore produce similar visible symptoms.

A conservative repair scope based primarily on visual observations may consequently encompass areas where invasive repair is ultimately unnecessary. RAS Engineering’s approach was different: Do not use the largest plausible damage area as the construction scope. Develop evidence to determine the actual repair area.

The RAS Forensic Funnel Method

RAS approached the investigation using its Forensic Funnel Method—a systematic process that begins with the performance of the entire building and progressively narrows the investigation toward assemblies, materials, and specific deterioration mechanisms.

Step 3 — Test the Materials

Targeted testing evaluated the physical condition of the materials. Depending upon location, evaluation includes concrete strength testing, reinforcing-steel mapping, corrosion evaluation, and examination of masonry, stucco, grout, and coatings.

A crack identified visually was not automatically translated into a large demolition area. Instead, the investigation sought physical evidence demonstrating whether the materials associated with that condition actually required structural repair.

Correlating Evidence to Define Repair Scopes

No single test was used to define the final restoration scope. RAS combined investigative methods and compared them along a clear hierarchy:

Observed Distress → Building Behavior → Assembly Condition → Material Condition → Structural Significance

Where multiple forms of evidence confirmed deterioration, repairs were specified. Where testing did not substantiate widespread deterioration, there was an engineering basis for avoiding unnecessary expansion of the repair scope.

How Forensic Engineering Reduced Construction Scope

RAS followed Approach B. On an 18-story coastal tower, unnecessarily expanding repair quantities affects far more than concrete alone. Reducing unnecessary repair quantities has a multiplier effect across demolition, steel treatment, formwork, coatings, swing-stage access, mobilization, resident disruption, and contractor overhead.

An Important Lesson for Condominium Boards

Engineering conservatism is essential when public safety is involved—but conservatism does not require replacing engineering investigation with assumptions. When adequate testing is unavailable, uncertainty requires broader and more conservative repair recommendations. A comprehensive forensic investigation reduces that uncertainty.

This case ultimately demonstrated that an unsafe-building determination did not automatically mean that the two towers required wholesale structural reconstruction. By progressing from whole-building behavior down to material testing, RAS provided an engineering basis for a focused, defensible restoration program.