Setbacks and building ratio: how to know the area you can build on your plot

Setbacks and building ratio: the two terms that decide the size of your house

The first thing I do when an owner sends me a plot plan is not to draw. It is to read two numbers: the setbacks and the building ratio. Before any design idea, these two numbers decide how much you can build on your plot, where, and how high. Anyone who exceeds them on paper finds out at the zoning committee and starts again.

This article explains both terms in plain words, how to read them from the zoning site plan, how slope and corner plots change them, and the general rules for the roof level and basement. You will not find numbers here, because the values differ between areas and their only reference is the Greater Amman Municipality or the relevant municipality.

What is a setback in building

A setback is the distance you must leave free of building between your plot boundary and the outer wall of the house, on each side. There is a front setback (on the street side), a rear setback, and two side setbacks. Its purpose is to keep daylight, air and privacy between you, the neighbours and the street, and to leave a path for maintenance and emergencies.

The actual buildable footprint on one floor is the plot area after the setbacks are subtracted on all four sides. On a narrow plot, two side setbacks take a large share of the width, which is why some houses end up long and narrow.

What is the building ratio

The building ratio is the maximum area of one floor (or of all floors combined, depending on how the zoning defines it) as a share of the plot area. If your plot is 500 m2 and the recorded ratio gave you half the area, for example, the most you could build on one floor would be 250 m2. That is an illustration of the arithmetic only, not a real value.

Alongside the building ratio comes another figure, the floor area ratio or the total area allowed across all floors, and the permitted number of floors. The three together define the size of the building.

How to read setbacks and building ratio from the zoning site plan

The document you need is the zoning site plan, obtained from the municipality by plot number, basin and village. It shows:

• The zoning class: residential A, B, C or D, or another zoning. Each class has a different minimum plot size, building ratio and setbacks.
• The setbacks in metres on each side of the plot.
• The building ratio, the floor area ratio and the number of floors.
• The width of the street the plot faces, because it affects some conditions.
• The permitted use: residential, commercial or mixed.

The land plan on its own (the one showing the plot boundaries and area) is not enough. You need the zoning site plan because it carries the building conditions, not just the shape of the plot.

How the slope of the plot changes the calculation

In Amman most plots are not flat. Slope affects two things. First, the level of the ground floor, from which the permitted height and the number of floors are measured. Second, the basement, because a sloping plot may allow a basement that is exposed on one side and buried on the other, and the rules for counting the basement in the building ratio depend on how much of it shows above ground.

That is why I always ask for a levels survey (a topographic survey showing the height of every point on the plot) before I start. On a sloping plot you may gain a full extra floor in the basement that is not fully counted, or you may lose a floor if the datum level is calculated differently.

Corner plots: two front setbacks

A corner plot faces two streets, and in most zoning regulations a front setback applies on each street side. That reduces the buildable area compared with a plot of the same size on one street, but it gives two exposed facades, better daylight and more options for the entrance and the garage. Some regulations give corner plots specific exceptions, and the reference is the municipality.

Roof level and basement rules in general

The roof level is the top floor, and it usually requires an additional setback from the front facade and sometimes from the other facades, plus a limit on its area as a share of the floor below. What remains of the roof slab becomes an open terrace.

The basement is the floor below the ground floor level, and it may be fully or partly buried. How it is counted in the building ratio and what uses are allowed in it (garage, storage, living) depend on the zoning and on how much of it is exposed. These two floors are what make up for a small footprint on small plots, and understanding their conditions early changes the whole design.

Why the architect checks setbacks before the first line

A design drawn before the zoning is checked gets redrawn. This is what I see in drawings sent to me by owners who tried to sketch the house themselves or with someone unqualified: a good-looking house on paper, rejected by the committee because a wall sits inside the side setback, or the building ratio is exceeded, or the roof level is not set back enough.

In my work every villa design or residential building project starts with a small table: plot area, setbacks, net buildable area per floor, number of floors, and the roof and basement conditions. Only then do I draw. When I prepare the building permit drawings, compliance with the zoning is already settled, and the file is submitted in coordination with a licensed engineering office without surprises.

What to do if the plot does not allow what you want

If the permitted area turns out smaller than you need, there are options before changing the plot: using the basement and roof level fully, designing a compact plan with fewer corridors, or revisiting the need itself. In some cases an exception can be requested from the municipality for a specific circumstance, but that is a separate process with its own conditions and no guaranteed outcome.

Summary: read the zoning before you dream about the design

Setbacks decide where you build, the building ratio decides how much, and the number of floors, roof level and basement decide the height and the total area. All the values are on the zoning site plan, and the final reference is the municipality.

If you own a plot and want to know what can really be built on it before designing, send the zoning site plan and I will reply with a first consultation.