Seawall height and code guidance
Find the wall measurement you need and check local height rules before raising or replacing your seawall.
- Top of the capMeasured from a fixed survey reference.
- WaterlineMoves as the water level changes.
- Survey reference (datum)A named reference, such as NAVD88.
Use the survey reference printed beside the elevation.
How high should your seawall be?
Your city or county may set a lowest or highest allowed elevation for the top of the wall. The rules can change with the property’s location and the work planned. Drainage, flooding and neighboring properties also affect the design.
For local height rules, use the top-of-cap elevation on your survey. This is the top of the wall measured from a fixed survey reference. It is different from the wall’s bottom-to-top height or the water level.
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
- 512.00 ft
- Survey reference (datum)
- NAVD88
This example shows 512.00 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? Choose “No / not sure” in the checker. Ask a surveyor to help find them; measuring from the water will give a different result.
What does NAVD88 mean?
NAVD88 is a fixed survey reference used to measure elevations, like a shared zero point. Another survey may use NGVD29 or a tide-based reference. To compare two elevations, they must use the same reference. A surveyor can help if the references differ. Read NOAA’s explanation of survey references.
Look for the seawall cap elevation on your survey or final construction plans. A flood certificate may show only the building’s elevation. If the wall measurement is missing, ask a surveyor; you do not need to measure beside the water.
Repair, replacement and permits
Before raising or replacing the wall, ask the permitting office which rules apply to the work. An engineer can check whether the existing wall, supports and drainage can handle the change. A higher wall can also change where rainwater flows.
Use the permit guide to find the Alabama Power, county, ADEM and U.S. Army Corps of Engineers contacts. Describe your location and planned work and ask which permits you need. Alabama Power’s application instructions explain the information needed for shoreline projects.
Common questions
How do I plan a change in wall height?
Start with your survey, the wall’s condition and the change you want to make. An engineer can check the supports, drainage and effects on nearby properties. Tell us about your plans and we’ll help you prepare the next step.
Is maximum height the height I must build?
A maximum is the highest allowed elevation, not a target you must build to. Ask your permitting office whether there is also a minimum for your property.
What if I do not know the elevation?
You can start with the property address and what you want to change. A surveyor can identify the top-of-cap elevation and its reference on your survey.
Can an existing seawall be raised?
An engineer needs to check the wall, supports and drainage before recommending a height change. The right approach may involve modifying the wall or replacing parts of it.
Does meeting a number mean the wall is safe?
Height is only one part of the wall’s condition. The supports, drainage and signs of damage also matter. Use the warning-sign check to prepare for an assessment.
How can I get help with the height?
Tell us the property’s city or county and what you want to change. Discuss the next steps, including whether you need a survey or seawall assessment. Confirm any service details and price before going ahead.
Smith Lake’s 510 and 522 contours are not wall-height targets
Alabama Power’s guidelines label summer full pool and fee ownership at 510 feet MSL, with a flood easement at 522 feet MSL. These describe reservoir and property-right references. They do not require a seawall cap at 522 feet or establish the safe height of a wall.
Ask the surveyor to identify the datum, benchmark, cap and adjacent grades. Have the designer and Alabama Power resolve the approved wall arrangement. Do not subtract today’s lake reading from a survey number with an unconfirmed reference.
Smith Lake residential shoreline guidelines · July 2025 · NOAA · Survey datum questions
A higher retaining wall is not automatically an allowed flood barrier
Raising a wall changes the loads, drainage and transitions that need review. Alabama Power’s residential guidelines separately prohibit levees and floodwalls on fee-owned and flood-easement lands. Describe the actual purpose and proposed work to the reviewer.
A survey and site-specific design should resolve the wall rather than a generic pass/fail height checker. Use the permit guide and property-record checklist for the records to gather.
Show sourcesHide sources
- Smith Lake residential shoreline guidelines · July 2025Source reviewed 2026-11-04
- NOAA · Survey datum questionsSource reviewed 2026-11-04
Ask about local requirements
Identify the property and the question to resolve. Keep any available survey with your planning notes.