Seawall caps in Islamorada

When a new cap is the right fix

A cap replacement suits a wall whose panels are sound but whose cap is cracked, spalled or too low.

• Cracked or spalled cap with rust staining
• Wall a little below the city's new height
• Panels separating at the top

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.

Caps are formed and poured above the water, but the tide decides how high the new cap must sit to give real freeboard.[1][2]

Seawalls and riprap inside the setback

Islamorada's shoreline setback keeps buildings 20 to 50 ft from mean high water, but it does not apply to seawalls, riprap and bulkheads whose purpose is erosion control or upland protection. Because the Keys are an area of critical state concern, the 2024 ordinance was approved by the Florida Department of Commerce.

Cap repairs and cap replacements usually take a lighter permit route than a full wall.[3]

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.

A new cap is often the cheapest way to reach that height, if the old wall can carry the extra weight.[4]

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.[4]

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.[3]

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.

Can the wall take a new cap?

Not always. Whether a cap can be added depends on whether the existing wall can bear the weight, which a marine or structural engineer must assess. A wall that cannot take it needs replacing instead.[7]

Permits for cap work

Miami-Dade DERM gives cap repair or replacement an expedited administrative authorisation when the building department has approved the structural plans. At the state level, seawall caps, batter piles and king piles used only to stabilise and repair seawalls fall under an exemption in rule 62-330.051(12)(d).[8][5]

Caps and city height rules

In Miami Beach a wall may be built to 4 ft NAVD if it is designed to support a future 5.7 ft NAVD, so the cap and footing need to be designed for that later raise. In Boca Raton the city must approve a location survey before the cap is poured, and a final engineer report confirms the cap elevation.[9][10]

Frequently asked questions