Miami-Dade wind loads, stamped 175 mph before you finish typing

Hurricane Andrew made Category 5 landfall at Homestead. A 169 mph gust was confirmed at the Fowey Rocks Light station before the anemometer failed. Roughly 49,000 homes were destroyed in south Miami-Dade.

The investigation that followed was the largest in US building-code history. Its conclusion: the storm did not exceed design — the design was set too low for the actual exposure of Miami-Dade's building stock.

175 mph entered the HVHZ amendment package as a local override above the map. Hurricane Wilma (2005) and Hurricane Irma (2017) both confirmed it was calibrated correctly, and it has stayed at 175 across every code cycle since.

Inside Miami-Dade you need a NOA — the county-issued Notice of Acceptance — not the statewide FL# Product Approval on its own.

The NOA is administered by the Miami-Dade Building Code Compliance Office (BCCO) and is a structurally different document.

Every envelope component carries one: impact glazing, exterior and garage doors, hurricane shutters, roof tile, single-ply membrane, underlayment, soffit, ridge vent, certain skylights.

Many manufacturers hold both, but a SKU that only carries FL# is non-permittable here even when the identical product is fine in Naples.

The output references the NOA pathway on every opening so the gap shows before submittal, not after.

They are the three legs of the HVHZ product-control tripod, and an assembly clears all three to earn a NOA.

• TAS 201 (Large Missile Impact) fires a 9 lb 2x4 lumber projectile — 50 ft/s for Level D below 30 ft, 80 ft/s for Level E on essential facilities and certain Risk Cat III/IV scopes.
• TAS 202 (Uniform Static Air Pressure) confirms the assembly holds design pressure with no permanent deformation and no water intrusion.
• TAS 203 (Cyclic Wind Pressure) drives thousands of gust reversals through the same assembly.

Products clear 202 and fail 203 routinely, because cyclic loading exposes fasteners, sealants, and frame corners a static test never reaches.

Hurricane Andrew — Category 5 landfall at Homestead on August 24, 1992, with a confirmed 169 mph gust at the Fowey Rocks Light station before the anemometer failed.

Andrew destroyed roughly 49,000 homes in south Miami-Dade and produced the largest forensic engineering investigation in US building-code history. The finding was that design was set too low for the actual exposure of the county's dense building stock.

175 mph entered the HVHZ amendment package as a local override above the ASCE map and has held across every cycle since. Wilma (2005) and Irma (2017) both confirmed the calibration.

The velocity finder applies 175 mph to every Miami-Dade ZIP automatically.

• Miami-Dade is the strictest: 175 mph county-wide, full HVHZ, NOA + TAS 201/202/203.
• Broward is the second HVHZ county at 170 mph — same NOA + TAS pathway, lower speed.
• Collier applies a 170 mph override but is non-HVHZ, so FL# is accepted and NOA is common but not required.
• Palm Beach is non-HVHZ and varies 165–170 mph by ZIP, oceanfront high and inland low.

Four counties, four rule sets — a project pulled from the wrong sibling's playbook gets rejected.

FBC 8th Edition (2023) took effect December 31, 2024 and references ASCE 7-22 throughout, so any Miami-Dade permit filed on or after that date is reviewed against 7-22; only legacy applications stay on 7-16.

The 175 mph override dominates the numbers either way, but three procedural changes land on every submittal:

• The new Partially Open enclosure classification with GCpi = ±0.18.
• The reorganized Chapter 30 C&C flow with refined effective wind area curves shifting corner-zone pressures.
• The 4 ft minimum edge strip "a" dimension that FBC R301.2(7) requires (3 ft is the ASCE 7-22 default elsewhere, and using it here is a common first-time rejection).

The engine runs 7-22 by default and bakes in the 4 ft Florida edge strip.

Not on the wind speed and not on product approval — both apply county-wide regardless of size. A 1,200 sq ft Kendall remodel and a 60-story Brickell tower are both governed by 175 mph and both need NOA-rated products.

The narrow exemptions cover non-envelope cosmetic work and a small set of like-for-like interior replacements; the moment a scope touches the envelope — window, door, shutter, roof recover — full HVHZ review fires.

The recurring surprise: an impact window approved in Houston, Charleston, or Naples needs a Miami-Dade NOA here, not a generic ASTM E1996 rating or a statewide FL#.

Plan review expects a Florida-licensed PE seal for almost anything beyond a straight like-for-like swap. Our in-house Florida-licensed P.E. signs and seals reports for Miami-Dade residential remodels up to 3 stories — single-family, townhomes, lanai retrofits, impact window/door packages.

For taller projects the structural engineer of record holds the seal and the calculator output is delivered as a working Engineering Report their team adopts.

The report is formatted for outside-PE review: clean inputs, intermediate steps, ASCE 7-22 chapter references, code block on page 1. A 50-state PE network covers out-of-state sealing where a project sits outside Florida.

Both use the same 9 lb 2x4 projectile; velocity and trigger differ.

• Level D fires at 50 ft/s — the standard Large Missile rating for openings up to 30 ft above grade on Risk Cat II projects.
• Level E fires at 80 ft/s — demanded on essential facilities (Risk Cat IV: hospitals, fire stations, EOCs), certain Risk Cat III projects, and anywhere the structural analysis calls for it.
• Above 30 ft the Small Missile pathway opens, a separate steel-ball test.

The report prints Risk Category and opening height on every line, so the fenestration vendor matches the rating to the right NOA-approved assembly.