Editor’s Note:  Original article updated to reflect the most recent changes to the calculations as per local Saint-Barthélemy government.

March 2021 Saint-Barthélemy — Good news, a helpful new feature has been added to xavierdavid.fr website as a tool for answering a frequently heard question on St Barts:  How much am I allowed to build on my property?  With that in mind, Bureau Xavier David has prepared this simple St Barts Real Estate Calculator* to assist anybody that is evaluating a piece of property.

Let’s walk through how to use it.  Here is a link to the calculator and what the page looks like:

It works in a few simple steps:

1. Enter a name or number for the property.  This is optional because the Calculator will work without it but it can be helpful to keep track of properties if comparing more than one.
2. Enter the size of the property in square meters.
3. Enter the approximate size of the green zone in square meters.  This can be estimated by consulting the zoning map as available on the website of the Collectivité.
4. If there is an Easement for right-of-way to a neighboring property, then enter the amount in square meters.
   
5. Choose one of four location categories:  Gustavia (Ug), Village (Uv), Residential (Ur) or Residential Special Zone (UrA).
6. Press Calculate and voila, the St Barts Real Estate Calculates automatically computes your Maximum Permissible Building Surface Area, Maximum Permissable Building Footprint, Minimum Permissible Permeable Surface Area, and Minimum Permissible Planted and/or Natural Vegetation Surface.

Now that we have had a look at the Real Estate Calculator, let’s try an example to see how it works.  Imagine that we have a property called Villa Example with hypothetical property number AB101.  For the sake of our example, this piece of land is 520 square meters and is approximately half in the green zone of the zoning map (i.e., 260 square meters) with an Easement of 50 square meters while located in a Residential (Ur) area.  These are the results:

1. Maximum Permissible Building Surface Area.  This is the maximum amount of surface area that can be submitted to the Collectivité on a Building Permit that will not be automatically rejected.  In our Villa Example test case, we are permitted to build up to 102 square meters.
2. Maximum Permissible Building Footprint.  In addition to total permissible surface area, the Collectivité also limits the size of the footprint of any single building.  This is the result of a communal preference for a series of smaller buildings in lieu of a single large construction. As per our Villa Example, 150 square meters would be the maximum size of a single building, however, as we are already limited to 102 square meters total then this restriction becomes a moot point in our example. 
3. Minimum Permissible Permeable Surface Area.  Additionally, as we pointed out recently in our article Introduction to St Barts Building Regulations, there are two more surface area factors that have direct impact on land development:  the first of which is Permeability.  Depending on the size of the of the parcel, 30–50% must remain permeable as per building regulations.  That means that it can not be paved or otherwise covered with a hard surface that interrupts the natural absorption of water into the terrain.  During rainfalls, hard surfaces create water runoff that often overwhelms the drainage of public roads and blocks traffic.  As per our Villa Example, at least 31.50 square meters of the property must remain unpaved, unbuilt and open to the absorption of rainfall.
4. Minimum Permissible Planted and/or Natural Vegetation Surface Area.  Lastly, depending on the size of the parcel, 40–60% must remain vegetation or Green space as per regulation.  Again, using our Villa Example the St Barts Real Estate Calculator informs us that at least 31.50 square meters must remain either natural vegetation or be planted as garden.

As a final feature of the St Barts Real Estate Calculator, please note that there is a button which will automatically generate a PDF version of the results that can easily be printed or saved for record keeping.  Feel free to try multiple properties for comparison sake.  Here’s the results of our test case :  Villa Example - AB101 :

We hope that this tool proves valuable to you but should you have any trouble with St Barts Real Estate Calculator or should you need further assistance in evaluating a piece of property on St Barts for a potential project then please feel free to contact us at Bureau Xavier David.

*The St Barts Real Estate Calculator is for estimation purposes only and is not a legally binding assessment of a project’s permissibility on St Barts.  Calculations are based on current regulation of the Collectivité of Saint-Barthélemy and remain subject to change.