Plan the right seawall elevation
Start with a surveyed cap elevation and the property’s permit authority. A number from a different Florida city cannot answer a Key Largo design question.
- Top of the capMeasured from a fixed survey reference.
- WaterlineRises and falls with tides and weather.
- Survey reference (datum)A named reference, such as NAVD88.
Use the survey reference printed beside the elevation.
What measurement does the designer need?
Find the top-of-cap elevation, its vertical datum and the survey date. Keep the original drawing, including its benchmark notes. NOAA distinguishes land-survey references from tidal datums; a photograph showing clearance above today’s canal water is not the same measurement.
- Mark cap elevations at low points and changes in direction.
- Include adjoining wall connections, yard levels and drainage outlets.
- Ask a surveyor to resolve conflicting references before comparing old and proposed elevations.
Who confirms a height change in the Upper Keys?
For a Key Largo parcel handled by Monroe County, submit the complete work description through the county process. Inside Islamorada, use Village Building Services and CityView. Have the designer identify the applicable shoreline and floodplain provisions for the actual property.
No single numeric minimum is asserted here. Request the controlling code section, the measurement reference and any conditions in writing. Keep that answer with the approved plans so the contractor is pricing the same design the reviewer considered.
Monroe County online permitting · Islamorada Building Services and CityView
Where will rainwater go after the wall changes?
A taller cap does not answer every flooding question. Monroe County notes that rain can compound high-tide flooding. Ask the engineer to draw the proposed drainage route and explain what happens when outside water is high.
Bring observations from both wet and dry weather. Record where water first appeared: over the cap, at an outlet, along a driveway or farther inland. Those observations help frame an investigation; they do not establish the cause by themselves.
Compare designs before comparing added height
Ask whether the existing panels, cap and supports can carry the proposed work, and what investigation supports that answer. Include the return walls, dock interfaces and neighbor transitions in the scope. A small cap addition can still involve more than concrete placement.
If the design affects submerged habitat or in-water work, resolve the environmental submission with the project professional before scheduling. Use the Upper Keys permit guide and quote checklist to keep design, approvals and construction allowances together.
What should you bring to a height discussion?
Bring the full survey, not a cropped elevation label. Circle the wall points you want to discuss and keep the legend and reference notes visible.
| Record | What to include |
|---|---|
Existing levels | Cap, yard, driveway, adjoining wall and relevant outlet levels, where measured. |
Reference | Survey date, units, vertical datum and benchmark information. |
Proposed change | The new cap level and the connections or drainage routes affected. |
Authority response | The applicable provision or written project-specific direction supplied by the reviewer. |
If an old drawing and a new survey appear to disagree, ask the surveyor to reconcile them before subtracting the figures. A photo showing water below the cap answers a different question from a surveyed elevation.
Ask the designer to explain what the height change improves and what flooding can still arrive by another route. Keep that explanation beside the proposal so added height is not mistaken for a promise to eliminate all flooding.
Find these two items on your survey.
Find the elevation for the top of the seawall cap and the survey reference used with it. The example below shows what to look for.
Seawall cap elevation
- Top of seawall cap
- 6.00 ft
- Survey reference (datum)
- NAVD88
This example shows 6.00 ft NAVD88. Use the number and reference on your own survey.
Match the value and the reference.
- The elevation: use the number for the top of the wall cap, not a building floor, water depth or the wall’s full height.
- The reference: copy the name beside the elevation, such as NAVD88 or NGVD29. You can compare elevations only when they use the same reference.
- Cannot find both? Ask a surveyor to identify both items. Measuring from today’s waterline cannot replace a surveyed cap elevation.
Show sourcesHide sources
- NOAA survey and tidal datum FAQSource reviewed 2026-10-25
- Monroe County online permittingSource reviewed 2026-10-25
- Islamorada Building Services and CityViewSource reviewed 2026-10-25
- Monroe County king tides and high tidesSource reviewed 2026-10-25
- NOAA nearshore submission and benthic assessmentSource reviewed 2026-10-25
Prepare a height question
Add the property location, available survey and the change you are considering. A local professional must confirm the design and applicable requirements.