So, you think you know what a BBL is?

Understanding the Building Baseline: A Lesson from the Field

When I first started working on residential projects in South Florida, I thought I had a pretty good handle on site planning — property lines, setbacks, easements, all the usual suspects. Then one day, a survey landed on my desk with a bold dashed line labeled “Building Baseline Line.” I thought, “Great, another way of saying setback.”

Turns out, it wasn’t that simple.

That dashed line — the BBL — isn’t the same as the property line or even the zoning setback. It’s something that can quietly change your whole project if you overlook it.

So What Is a Building Baseline Line, Really?

Think of the property line as the legal edge of your land — the line that separates what’s yours from what isn’t.

Now, the BBL is something else entirely. It’s usually drawn about five feet in from the property line and establishes the starting point for measuring the setback. In other words, it’s the line from which all building placement is calculated — a reference for the minimum distance your structure must sit from the edge of the property.

In many South Florida neighborhoods, that BBL is drawn directly on the recorded plat, often decades before your project even comes into play. It quietly dictates the building envelope for every home on the street, long before any zoning or design discussions happen.

The Surprise Factor

Here’s where the lesson comes in.

A few years back, I was helping a homeowner in Little Haiti with a renovation and small addition to an older single-family house. The zoning code allowed a 20-foot front setback, so it seemed straightforward. But when I reviewed the property plat, I noticed a BBL about five feet in from the property line — meaning the setback had to be measured from that line, not the property line itself.

That small detail changed the placement of the addition and the way the front yard interacted with the street. Because the BBL is part of the recorded plat, it wasn’t something the city could easily waive.

It was one of those moments that reminds you: in architecture, the smallest line on paper can have the biggest impact in the field.

Where You’ll Find It

BBLs are especially common in:

• Miami-Dade County, particularly in older neighborhoods like Little Haiti, Buena Vista, and The Roads, where plats often included building control lines.

• Broward County, in master-planned communities such as Weston and Parkland.

• Palm Beach County, in newer developments where consistent building placement is part of the design intent.

You’ll usually find the BBL on the property survey or the recorded plat, drawn as a dashed line parallel to the property line and labeled with a dimension (for example, “5’ BBL”).

Why It Matters

Here’s the takeaway:

Even if zoning says one thing, the plat may be stricter, and the plat always wins.

So before sketching that first concept or promising a client how much they can expand, take a minute to look for that BBL. It might just save you a lot of rework — and a few uncomfortable conversations later.

A Small Line with a Big Lesson

To this day, every time I review a new property survey, my eyes go straight to the fine print and dashed lines. Understanding where you can’t build is just as important as understanding where you can.

And that’s the kind of detail that quietly shapes good design — a lesson you only need to learn once.