Why does concrete spall in South Florida — and what should your board do about it?

Published: September 21, 2026 · Last reviewed: September 21, 2026

Direct answer: One major cause of concrete spalling in coastal buildings is corrosion of the steel reinforcement inside. Corrosion products occupy more volume than the steel they consume, exerting pressure that cracks and breaks away the surrounding concrete. Visible spalling needs a qualified assessment to determine its cause, extent, and the right repair.

Spalling is one of the most common things a South Florida board will ever see on its building — and one of the most commonly misread. Corrosion-related deterioration can develop for years before damage becomes visible, but the appearance of a spall does not tell you how long the process has been running, how fast it will progress, or whether the affected area is safe. Those are exactly the questions an assessment answers, and they are worth understanding before deciding what to do.

Before documentation, budgeting, or anything else on this page — if concrete is loose, cracked overhead, or has fallen, keep people away from the affected area and notify property management promptly. Falling concrete is a hazard in its own right, separate from what the spall says about the structure. Do not tap, chip, or probe loose material; arrange a qualified assessment rather than waiting for the next scheduled inspection, and document the condition only from a safe location. An apparent immediate danger warrants emergency assistance.

Spalling is concrete cracking, flaking, or breaking away from a structure — most visibly at balcony edges, slab undersides, columns, and parking garage ceilings. The critical point for a board: a spall is the visible result of a process, not the process itself. Chipping off loose concrete and patching the hole treats what you can see. Whether the cause is still active behind the patch is a separate question, and it is the one that determines whether the repair lasts.

Reinforced concrete pairs two materials: concrete, strong in compression, and steel bars (rebar) that carry tension. Hardened concrete's alkaline environment helps protect that embedded steel by maintaining a passive layer on the bar.

Two mechanisms can break that protection. Chlorides — abundant near the coast, where airborne salt dissolves into water moving through the concrete's pores — can disrupt the passive layer directly. Carbonation — a slow reaction between the concrete and carbon dioxide in the air — can reduce the concrete's alkalinity over time. Where protection is lost and moisture and oxygen are available at the bar, the steel can corrode.

The concrete between the outside face and the bar — the cover — is the steel's main defense. Where cover is thin, cracked, or was built thinner than designed, exposure reaches the bar sooner.

Corrosion products occupy more volume than the steel consumed — published forensic references describe expansion of up to several times the original bar volume. That expansion happens inside a rigid material with nowhere to go, so it exerts pressure on the surrounding concrete until it cracks and breaks away. New cracks can then admit more moisture and chloride, which is why deterioration, once active, deserves diagnosis rather than deferral — though the rate at any particular location depends on exposure, materials, and cause, and cannot be read off a photograph.

Spalling alone does not establish a building's overall safety — in either direction. Its significance depends on location, extent, and the condition of the concrete and reinforcement behind it. A dramatic-looking spall may prove to be shallow damage with sound steel behind it; a modest crack in a structurally sensitive location may matter more. A qualified assessment is what determines the appropriate response.

Florida's milestone inspection law is deliberately precise here. "Substantial structural deterioration" means substantial structural distress or substantial structural weakness that negatively affects a building's general structural condition and integrity — and surface imperfections such as cracks and peeling finishes do not meet that bar unless the licensed professional performing the inspection determines they are signs of it. Milestone inspections are performed by a Florida-licensed engineer or architect; that professional, not a visual impression, makes the call.

One distinction worth keeping separate: whether a condition triggers a Phase 2 milestone inspection is a statutory classification. Whether it needs repair or protective measures now is a practical engineering question. A condition can fall short of the statutory threshold and still be worth addressing promptly.

NIST's technical findings, released June 22, 2026, concluded the 2021 Surfside collapse most likely initiated with punching shear failures — failures at slab-to-column connections — at two garage columns under the pool deck. NIST attributed the low margins against failure primarily to severe deviations of the original structural design from the codes and standards of the day and to construction that deviated from the design drawings, with long-term corrosion degradation, added loads, and deck modifications further diminishing those margins over the building's 40-year life. NIST's final report is still to come.

Two things follow for boards, and they cut in different directions. An ordinary observed spall does not carry Surfside-scale risk, and nothing in NIST's findings says it does. At the same time, the collapse involved conditions that accumulated across a building's whole life — which is why Florida's inspection framework now examines aging buildings systematically rather than waiting for symptoms to become alarming. (That reading is ours, not NIST's.)

Manage the exposure first. If material is loose or overhead, keep people clear and get a qualified assessment moving — see the first section above.

Then document. Photograph locations from safe positions, note dates, and keep the record. Patterns across a building tell the assessing professional more than any single spall. Prior inspection reports, repair drawings, photographs, and maintenance records all help that professional understand the building's history.

Let the assessment define the investigation. The assessing engineer determines what is needed to define the repair — which, depending on the condition, may include reviewing records, examining reinforcement, mapping damage, and testing the concrete. Repairs designed against a diagnosed cause are how you avoid renewed deterioration next to a patch, a risk ACI documents for repairs that don't account for the electrochemical conditions around them. Properly designed local repairs can be entirely appropriate.

Connect it to your compliance picture. If your building is approaching its milestone inspection — administered through the recertification programs of the authorities having jurisdiction in Broward and Miami-Dade (see deadlines by jurisdiction) — documented concrete conditions are exactly what the inspecting professional will evaluate. Boards that arrive with records get better answers. Assessment findings should also inform maintenance and reserve planning; a Structural Integrity Reserve Study includes a visual inspection and supports reserve planning, though it is not a substitute for a targeted investigation of a specific deteriorating condition.

Is spalling common in South Florida? Common to observe, yes — the coastal environment is aggressive toward reinforced concrete. Whether corrosion is active in a particular building, and how far it has progressed, is what an assessment determines; commonness is not a reason to ignore it.

How fast does spalling get worse? The rate varies with exposure, material condition, and the underlying cause. A photograph cannot establish a reliable progression timeline — which is an argument for diagnosis, not for alarm.

Can spalling be painted or sealed over? Painting over a spall does not repair damaged concrete or reinforcement, and it does not establish the cause. Coatings have legitimate protective uses on sound, assessed concrete; assessment comes first.

Does spalling automatically trigger a Phase 2 milestone inspection? No. A Phase 2 is triggered when the Phase 1 professional finds substantial structural deterioration as the statute defines it. Surface damage alone does not meet that threshold unless the licensed engineer or architect determines it signals deeper distress. Separately, a condition that doesn't trigger Phase 2 may still warrant repair.

Who should look at it — a contractor or an engineer? Both have roles, in order. A licensed professional diagnoses cause, extent, and repair scope; a qualified contractor executes the specified work and often contributes valuable field observations along the way. Getting assessment and construction in the right order is what protects the repair budget.

This article is educational and general in nature. It is not engineering advice for any specific building; conditions vary, and only an assessment by a licensed professional can evaluate a particular structure.

Reviewed by Gabor I. Nagy, PE — Founder

Fortis BuildSafe Solutions is a forensic engineering firm serving condominium associations, cooperatives, and property owners across Broward, Miami-Dade, and Palm Beach counties. If your building is showing concrete damage and you want to understand what it means before deciding what to do about it, we can help you establish where the building actually stands. Contact Fortis.

• Florida Statutes §553.899 (2026 edition), Mandatory structural inspections for condominium and cooperative buildings — https://www.flsenate.gov/Laws/Statutes/2026/553.899 (verified September 21, 2026; section history ends with the 2025 amendment, ch. 2025-175).
• FHWA, Corrosion of steel in concrete — mechanism review — https://www.fhwa.dot.gov/publications/research/infrastructure/structures/04093/01.cfm (accessed September 21, 2026).
• Robson Forensic, "Concrete Spalling — Expert Article" — https://www.robsonforensic.com/articles/concrete-spalling-expert-article (accessed September 21, 2026). Corrosion-product expansion (upper-bound figure), concrete cover, chloride mechanism.
• NIST, "NIST Releases Technical Findings on What Caused the 2021 Partial Collapse of Champlain Towers South," June 22, 2026 — https://www.nist.gov/news-events/news/2026/06/nist-releases-technical-findings-what-caused-2021-partial-collapse (accessed September 21, 2026).
• ACI RAP Bulletin 8, introduction (electrochemical conditions around concrete repairs) — https://www.concrete.org/portals/0/files/pdf/rap-8.pdf (accessed September 21, 2026).