Posted: Jul 20, 2022
How To Buy an Offshore Island in the Florida Keys

You won the Lotto. Or, you're quiting your job, selling all your stuff and moving to the Florida Keys. Or, island property you vaguely remember visiting with your Grandfather when you were a kid is available through an estate after probate.  Regardless, you somehow want to sell or buy an undeveloped offshore island and build a durable, environmentally friendly, on-the-water retreat for year 'round or getaway living. How do you find an island for sale, determine if it can be developed, obtain the permits to develop and get going on your mid-life dream? Easy. Sort of.

How to Find an Island For Sale.

Hardly any Multiple Listing Service (MLS), the system that lists properties For Sale and Sold, has an extensive number of island properties listed For Sale.  Hence, systems like Zillow and Trulia are likewise not going to have much to show either - they're primarily reflections of the properties shown in the MLS.


The MLS that serves the Florida Keys can be searched for Islands for Sale but rarely are there more than a handful available. It is also not unusual for a property that is entirely on land to be incorrectly atrributed to be an island as some Realtors magically expand their search for a Buyer.


You can Google search "islands for sale" and pick your geographic area.  The resulting web pages will be a mishmash of individual islands formerly or currently for sale, real estate companies that might at one time have had an island for sale and the occasional island that actually is on the market for sale. Maybe you'll find an old out-of-date blog of mine!


Or, like me, you could find the data base of island owners in the Keys (510 individual island properties documented by Monroe County) and write a letter as I did to the 60 non-government owners whose island has a minimum of 5 acres, asking if they are interested in selling their offshore island property.


Caution - Be careful when reading the Real Estate (RE) Number of island property.  Often that real estate number includes underwater or "bay bottom" property.  The outline of the perimeter of the property that comprises the RE Number might contain 20 acres but 16 acres of that could be underwater bay bottom.

So What Are We Really Talking About


After weaving my way through the Monroe County Land Development Code (MuniCode) and its rules and regulations for developing an offshore island and talking with multiple County officials, it became pretty clear what are the basic criteria for development.  The two primary rules for developing an offshore island that has no previously existing house, hut or other "Dwelling Unit" (DU) are:


  1. An offshore island must have a minimum of 10 dry acres of land - upland as it is called. If the island does not have a minimum of 10 upland acres then the County is very unlikely to allow development. One Dwelling Unit (DU) is required to have 10 acres.
  2. Development of these 10 or more acres is limited to 5% of the total upland acreage; i.e. 95% of the upland area must remain Open Space.

Facts and Figures - Environment

Refering to the MuniCode - Any property to be developed must comply with multiple environmental considerations; namely,


Section 118 - 7. General Environmental Design Criteria.  This Section details the necessities of maintaining protected habitat for plants and animals, species of special concern and regionally important native plants. Subsection 7(f) (1) and (2) details the practice of "clustering" development in order to minimize impact on all species. Development is prioritized to occur on the least sensitive of habitat types (habitat types listed a. - j.).


Facts and Figures - Development


Section 130 - 42.  Purpose of the Offshore Island District (OS) is to establish areas that are not connected to US 1 as protected areas, while permitting low intensity residential uses and campground spaces in upland areas. US 1 is the sole highway in the Keys and travels from Homestead on the southern tip of "the mainland" to Key West.

Section 130 - 90. Offshore Island (OS) District. There are eight permitted uses in the OS District though only two apply here.  They are:


  1. Detached Dwellings
  2. Camping, for the personal use of the owner of the property on a temporary basis.
  3. The rest of the permitted use options vary from bee keeping to special tourist housing uses to satellite earth stations.

Residential Density and Open Space Requirements


Section 130 - 157.  Maximum permanent residential density and mimimum required open space shall be in accordance with the above table:


  1. Allocated Density for Offshore Island (OS) is .1.  That is, 1 Dwelling Unit (DU) divided by 10 acres equals .1.
  2. Minimum Open space Ratio is .95. That is, 95% of the upland area must remain Open.


Let's Get Going


Suppose you or your family own an island in the Florida Keys and you are interested in knowng about its saleability. The Monroe County Property Appraiser Office is a good place to start. Tell them the name of the owner of the property and if you have it though not required, a Property ID number. By measuring the dimensions of the island  they can give you a good idea on how much land mass is associated with the property. Not wet or dry land just approximately how much mass there is. Their number is 305.292.3521.


A good surveyor can eyeball the land mass through their software and professional experience and tell you if the land mass appears mostly wet or dry. A lot of islands in the Keys are merely dense clusters of mangroves and wet land trees, rooted into shallow water with little actual dry land as part of the island land mass.  I use Florida Keys Land Survey. They'll probably use a drone for an aerial survey. Call 305.360.3690.


If it looks like you have 10 upland acres you'll next need an Development Feasibility Analysis.  Two choices; one private company and one public:


  1. Terramar Environmental Services. Call 305.393.4200. 
  2. Monroe County Planning and Environmental Resources. Bruce Franck. 305.289.2561


If you are still in the game with 10 environmentally clean upland acres, its time to go to the Monroe County Planning and Development people. Call Brad Stein at 305.289.2507.  Planning and Development controls the approval process and provides the guidance for managing the development of the project.



Worst case is - you own an island but it does not have 10 acres of dry land.  Your Grandfather bought the island in the 50's or 60's and took your Dad and your Uncle there to camp and fish but never built anything. Cool, old timey B&W photos of your Dad and Uncle Bob when they were young men; but, ends up, there's only a couple upland acres of dry land - if that.  So it can't be developed.  And no one is going to buy it.  Now what?


Sell it to the government.


The Monroe County Land Authority occasionally purchases undeveloped land for conservation and recreation. Call Mark Rosch at 305.295.5180.  If not the County, then maybe the state or some federal agency will be happy to buy the island and preserve it's use for environmental purposes. I can help you with that.


Many thanks to the following people for helping me write this article:


  1. Dee Dee Harnish, Director, Valuation Services, Monroe County Property Appraiser
  2. Brad Stein, Planning and Development Review Manager, Monroe County Planning and Environmental Resources
  3. Tim Douma, Principle Biologist, Monroe County Planning nd Environmental Resources
  4. Bruce Franck, Senior Biologist - Supervisor, Monroe County Planning and Environmental Resources
  5. Mark Rosch, Senior Property Acquisition Specialist, Monroe County Land Authority


If you run aground in your efforts to find the information you are looking for, please contact me here or call me anytime 305.942.1040.


Good luck!


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