Flood vents in Islamorada
Flood vents in Islamorada, where the 2005 flood maps still apply while new ones wait.
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We install flood openings in garages, crawlspaces and enclosures below the flood level, sized to the NFIP rules.
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The short answer
FEMA's NFIP rules for flood openings call for at least 2 openings on at least 2 walls, a total net area of at least 1 square inch for every square foot of enclosed area subject to flooding, and the bottom of each opening no higher than 1 ft above the adjacent grade. Islamorada's effective flood maps date from 18 February 2005, and FEMA has not yet set a date for the preliminary maps appealed in 2021.
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Who needs flood vents
Owners with garages, storage rooms or crawlspaces below base flood elevation in A zones.
Flood maps from 2005, new ones pending
Islamorada still builds to effective flood maps dated 18 February 2005. Preliminary maps went through appeals between March and June 2021, FEMA has not announced when they take effect, and the Village has promised six months' notice once it does.
Vents are sized to FEMA's one square inch per square foot rule for the enclosed area in your zone.[1]
Watch the datum: about 1.5 ft
The Village notes that converting from NGVD29 to NAVD88 shifts elevations by about -1.5 ft on average in Monroe County, and the shift varies from place to place. Old plans and new maps use different datums, so a cap or floor height has to be converted before anyone compares numbers.
Vent openings sit within 1 ft of grade, so local elevation datums matter when they are placed.[1]
Bay side and ocean side tides differ fourfold
NOAA's Florida Bay gauge at Upper Matecumbe Key shows a great diurnal range of only 0.61 ft, with mean higher high water about 0.41 ft below NAVD 88, while the Hawk Channel gauge a short way across the key shows 2.28 ft (1983 to 2001 epoch). A lift or floating dock sized for one side of Islamorada is wrong for the other.
Those tide levels show how close high water already gets to the enclosure.[2][3]
What makes Islamorada different
Principal buildings sit 20 ft from the mean high water line on altered shorelines such as canals, 30 ft on open water with conditions, and 50 ft on unaltered shorelines. Docks, lifts, davits, seawalls and riprap are water-dependent structures that may sit inside that setback under the Village's standards.[4]
Sanctuary and manatee layers
The federal small-project permit, SPGP VI, required Sanctuary sign-off before any Islamorada project in Keys waters, and crews follow the state manatee conditions on every in-water job.[5][6]
Permits in Islamorada
- Islamorada, Village of Islands, Planning and Development Services: Docks, lifts and shoreline structures under Village Code Chapter 30.
- Florida Keys National Marine Sanctuary: Sanctuary waters surround every Islamorada key from the mean high water mark; we confirm what Sanctuary approval each project needs.
- Florida DEP or South Florida Water Management District: State permit or exemption; part of the Village's water is the Lignumvitae Key Aquatic Preserve.
- US Army Corps of Engineers, Jacksonville District: Federal authorisation for work in the Sanctuary waters around the Village.
Sizing flood vents
A 400 sq ft garage needs at least 400 square inches of net open area, split across at least 2 walls, unless engineered vents carry a design certification for a smaller area. FEMA says designs must either carry a certification or meet the prescriptive criteria.[7][8]
| Rule | Requirement |
|---|---|
| Number | At least 2 openings on at least 2 walls |
| Size | At least 1 sq in net area per sq ft of enclosed flood-prone area |
| Height | Bottom no higher than 1 ft above adjacent grade |
| Garage doors | Do not count as flood openings |
Frequently asked questions
Which flood maps apply in Islamorada?
The effective maps dated 18 February 2005. Preliminary maps were appealed in 2021; FEMA will give six months' notice before they take effect.
Why do elevations on old Islamorada plans look different?
They may be in NGVD29. The Village says converting to NAVD88 shifts elevations by about -1.5 ft on average in Monroe County.
Why does it matter which side of Islamorada I live on?
Because the tide is very different: about 0.61 ft great diurnal range on Florida Bay and 2.28 ft on Hawk Channel, per NOAA gauges at Upper Matecumbe Key.
Sources
- Floodplain Management, Islamorada, Village of Islands, Building Department. Accessed October 28, 2026.
- Datums for station 8723808, Islamorada, Upper Matecumbe Key, Florida Bay (tidal epoch 1983 to 2001), NOAA Center for Operational Oceanographic Products and Services (CO-OPS), Tides and Currents. Accessed October 28, 2026.
- Datums for station 8723814, Upper Matecumbe Key, Hawk Channel (tidal epoch 1983 to 2001), NOAA Center for Operational Oceanographic Products and Services (CO-OPS), Tides and Currents. Accessed October 28, 2026.
- Ordinance No. 24-15 amending Village Code Sec. 30-1542 Shoreline Setback, with Department of Commerce Final Order COM-24-043, Islamorada, Village of Islands. Accessed October 28, 2026.
- Department of the Army State Programmatic General Permit VI (SPGP VI), SAJ-2015-2575, State of Florida, U.S. Army Corps of Engineers, Jacksonville District (document hosted by Florida DEP). Accessed October 27, 2026.
- Standard Manatee Conditions for In-Water Work (2011), Florida Fish and Wildlife Conservation Commission (FWC). Accessed October 27, 2026.
- Proper Openings: Enclosures (Applicable to Zones A, A1-A30, AE, AO, AH, AR and AR Dual) (glossary), Federal Emergency Management Agency (FEMA). Accessed October 27, 2026.
- Openings (glossary), Federal Emergency Management Agency (FEMA). Accessed October 27, 2026.
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