The Most Important Terms to Know : Plot Ratio & Density

Today, I would like to talk about the plot ratio and density. These are key items that determine how packed a city can be. In many countries, the closer you are to the main center of the city, you can see building being higher and higher. This has a lot to do with how a city is planned using plot ratio and density.

Image by Izuddin Helmi Adnan via Unsplash.com

So what is plot ratio and density? When I was a student studying urban planning, truth be told – this is the hardest thing to explain. You easily get lost in all the technical jargons.

However, as a practitioner, as a professional, I’ve learned that plot ratio & density is very important. This is essentially where the money is for developers – and this is also essentially where local authorities will have the most control. Most importantly, for every public participation programs your local authority organizes, as a member of the public, this is where you should be most critical. To understand these two terms is to really understand development.

Why plot ratio and density? Why not one or the other? Actually, plot ratio and density are almost the same, in which they determine the size of developments, however, the usage for both is different.

Let’s start with density.

Density is only used for residential developments. Why? Because it is easier to estimate the number of population in a residential than in any other types of development.

How is density calculated? The method is pretty straightforward if you compare it with the calculation of plot ratio. You need to have two variables – number of residential units and estimated population per residential unit. Each local authority would have their assumed population per residential unit.

For instance, KL uses 4 persons per unit, while Selangor uses 5. In a development of 100 units, for KL – no matter the size and the actual number of people living inside it, it is automatically assumed that you have 400 persons (4 x 100 units) living in it, while in Selangor it is assumed that you have 500 persons (5 x 100 units).

However, in local plans, the unit used is ppa (population/persons per acre) – but you will not get the number if you don’t have the number of residential units.

So let’s say you have a development in KL which is on a land with the area of 2.5 acres, and with 100 residential units altogether. Your development density will be as per the calculation below:

Number of residential units : 100

Number of population (KL uses 4 per unit) : 100 x 4 = 400

Area : 2.5 acres

Ppa : 400/2.5 = 160ppa

This is especially important to note when you review your local authority’s plans for your locality. You would want to know whether your local authority has allowed for a sky-scraping tower be built opposite your home or school.

Now you know what density is, what is the density of your own residential area?

I started with density because it is easier to understand. So let’s move on to plot ratio. Plot ratio is used for developments other than residential. We use plot ratio because we can’t properly estimate the number of persons for each unit – and may include large plots such as factories and other commercial & industrial activities.

To make it easy to understand, let’s see what words that are included in the term.

Plot: Easily the area of the plot of land

Ratio : Ratio here refers to the ratio of development

In simple terms, plot ratio is the ratio of development to the area of the plot of land.

If we say the plot ratio is 1:2, it means,

1 : Area of the plot of land

2 : Size of development (gross floor area)

To make the “size” of development measurable, we use the gross floor area to calculate it. Gross floor area is the total of floor area for a development building, including corridors, facilities etc.

If we take it back to plot ratio of 1:2, we can put this as example:

A commercial development with the gross floor area of 4000 square feet on a plot of land of 2000 square feet is considered as a development with the plot ratio of 1:2.

Let’s break it down:

A - Area of the plot of land : 2000 square feet (2000/2000 = 1)

B - Gross floor area : 4000 square feet (4000/2000 = 2)

Hence A:B is 1:2.

Plot ratio has been used for so long. This is an example you can find in Plot Ratio, A Plan To Combat Congestion In London, London County Council, 1957:

You can see that although a plot ratio is set, there are many ways to develop it.

However, in Malaysia, generally, a development is built on only half of the land plot to make way for fire safety and green areas.

Your local authority, in their 5-year plans would have gazette the plot ratio and density allowable for a certain land. Developers may appeal to have more plot ratio / density and this may or may not be approved by your local authority. Usually, for approval, a huge sum of development charges are paid to the local authority. Your knowledge on what plot ratio and density entails will help you to understand the development direction, and will prepare you for the impacts that may come.

Please look at density and plot ratio when you see any public participation booths that require your feedback. Sometimes you think you’re so helpless when it comes to navigating the path of development in your area, but knowing this means you can comment – you can agree or disagree, you can voice out your concerns - all for the betterment of your locality.

I hope I have shed some light on (what I personally think are) two of the most important terms in development.

Now, what do you think is the highest plot ratio in KL?

Hint is in this article : https://www.theedgemarkets.com/article/plot-ratio-cap-could-impact-developments-kl