Not everyone knows that when buying land to build, you have to think about what kind of construction you want to do. This planning is necessary because each lot has its occupancy rate, soil permeability rate and utilization coefficient. Have you ever heard of these terms?
Well, all cities are divided into zones. Each of these zones has its soil permeability rate, occupancy rate and utilization coefficient, determined by the city’s urban planning team.
The purpose of these parameters is to manage each area of the city better. In other words, the government manages to control more efficiently the growth of a certain area of the city.
That’s why when buying your land you need to know these parameters, since each zone allows a type of construction. You can’t just build a building in an area where only houses can be built.
But this is a basic example. See below for more details on the parameters of occupancy rate, soil permeability rate and utilization coefficient.
What is occupancy rate?
The parameters of occupancy rate, soil permeability rate and utilization coefficient are percentages relative to the area of each land. Therefore, to be able to know what this percentage is for your land, you need to have the square footage of the land in hand.
But, specifically about the occupancy rate, it is calculated based on the area that your construction will occupy within the land. Only there is a detail. It is not only considered the footage of the ground part of the construction.
If by chance you intend to build a two-story house, and the second floor extends to an area beyond the one occupied by the ground floor, you have to consider this extra occupation also when calculating.
Information on soil permeability rate, occupancy rate and utilization coefficient are available on each city’s website or directly at the city hall. This is public information, but there is usually a fee for consultation, which is usually cheap.
Even though you have to pay, you need to consult about these fees before you buy your land and end up getting a bad deal. So, go to the city hall and ask for assistance in the urban planning zoning sector.
The calculation of the land occupation rate is done with the following formula:
Total area of the ground floor + total area exceeding the other floors / total area of the land
See the example considering a plot of 300m 2:
To build a one-story house: if your one-story house has 120m 2, you should calculate 120m²/300m² = 0.40. This means that the house will occupy 40% of the land.
To build a house with two floors: if your house has a ground floor with 70m 2 and the second floor has 120m 2 , you should calculate 70m² + 50m² (surplus area) / 300m² = 0.40. This means that the house will occupy 40% of the land.
However, who determines the occupancy rate of your land is the city hall. So, it’s no use designing your house before you know the maximum occupancy rate that your building will be able to occupy.
If the city has determined that, in its area of land, only houses with up to 70% occupancy rate can be built, it is mandatory to comply with this determination. That’s why it’s essential to do research at the city hall before doing anything else.
After the occupancy rate, there is also the soil permeability rate.
It is the ratio between the total area of the land and the area penetrated by rainwater. This is a very important rate to prevent flooding and flooding. So, it is mandatory to respect it even for the sake of public safety.
The rate determined by the city in this case varies greatly depending on the type of zone, whether it is an urban center or rural areas. And each city determines a fee.
But basically, the minimum rate in urban areas is 15%, while in rural areas it can exceed 70%, just to get an idea.
The calculation made to determine this rate is as follows: permeable area defined by the city hall x total land area.
What are considered permeable areas are the areas where rainwater can penetrate? Therefore, sidewalks, swimming pools, waterproof decks, sports courts and covered areas with marquises and eaves are excluded from the calculation.
See an example of calculation: with the land of 200m 2 and a permeability rate of 15%, the account is 200m² x 15% = 30m² which will be your minimum permeable area.
This means that if you are going to build an 80m 2 single story house with a sidewalk area of 20m 2 and a party area of 40m 2, the total non-permeable area will be 140m 2.
Thus, 60m 2 of permeable area remains in relation to the total of 200m 2 of your land, which is within the allowed for your land. Will be able to build.
But, if by chance you intend to build a 180m 2 house on the same land, there will only be 20m 2 of permeable area left. In this case, your architect will have to reformulate the project, making adaptations, as it will not be approved by the city.
Of course, architects already know this. So, generally, they themselves obtain the information on soil permeability rate, occupancy rate and utilization coefficient from the city hall.
Thus, they will already know what you can and cannot build on your land. Even so, it is important that the client is also aware of the importance of these fees so as not to make future mistakes in any renovation, for example.
Whenever you want to expand the house or do any type of new construction, you must again approve the project with the city.
Currently there are different technological solutions for you to be able to build more on your land, without disturbing the allowed permeability rate. These solutions are the permeable floors, which allow the penetration of rainwater in uncovered areas.
It is interesting that, when hiring an architect for a project, he knows not only what is mandatory, but also the occupancy rate and other calculations to be done. But yes, that you are also aware of these smart and sustainable solutions that help to optimize the project.
Well, the occupancy rate and the soil permeability rate are just two of the concerns you need to have before thinking about your construction project. The other calculation is the achievement coefficient.
It is the relationship between the land area and the total built-up area. In other words, it will determine the total area that can be built. After all, you might want to make a garage or a party area, for example.
So, see how the calculation works, considering, again, a plot of 200m 2:
To build a house with three floors: assuming each of the three floors is 120m 2, you should calculate (120m² x 3 floors) / 200m² = 1.8. This 1.8 is your achievement coefficient.
To build a house with 1st floor of 70m 2 + 2nd floor of 80m 2 + garage of 50m 2 , you must calculate (70m² + 80m² + 50m²) / 200m² = 1. This 1 is your utilization coefficient.
In the same way that it works for the occupancy rate, it is also the city hall that determines the coefficient of use of your land. Here are some important information to take into account when making this calculation: