 February 6, 2023

# RAMP CALCULATION

February 6, 2023

The ramp calculation is one of the most important steps to determine the success of its functionality, a fact that usually causes concerns among several professionals.

In addition to a good aesthetic, the ramp is an architectural element that must be able to overcome a certain gap, in a functional and safe way.

Its calculation is relatively simple, but according to its application it is necessary to meet some standards, such as NBR 9050 (Accessibility in buildings, furniture, spaces and urban equipment).

But don't worry, in this post you will find all the information and also a step by step to calculate your ramp ensuring comfort, safety and also some important tips, check it out!

## WHAT CHARACTERIZES A RAMP?

A ramp is a circulation element that aims to connect two floors with different levels, allowing the traffic of people, cargo or even vehicles.

Observing its different usages, we realized that the ramp calculation can vary according to the needs of the project and the type of user, therefore we need to observe some important aspects, such as:

• Available space and possible obstacles to execution;
• Appropriate slope, length and width;
• Distance between the different levels;
• Probable users;
• Surface material;
• Execution cost;
• Approach area and ramp access;
• Position of handrails and guardrails;
• Compliance with technical and safety standards;
• Alternative means of access.

With this basic information it is already possible to do the correct dimensioning, so let's learn how to do the ramp calculation.

## HOW TO CALCULATE RAMP?

Regardless of the needs that a ramp will meet we have some common aspects for any type of ramp which are its inclination, height and length.

The ramp slope value is expressed as a percentage (%), which is obtained by the ratio of the exceeded height  (h) multiplied by 100 and divided by the length (c).

However, in construction work it is common to find different situations, for example, you have a predefined inclination and need to find the height or length.

At first it may seem complicated but it is actually quite simple, as we can solve it with a simple rule of three. Let´s see.

## RAMP CALCULATION EXAMPLE

To do the ramp calculation we need as much information as possible, because based on the result obtained, we need to check if the dimensions meet the needs of the project and the corresponding technical standards.

Of course, the first step is precisely to identify the basic information that is height, length and slope, so let's learn how to use the formula below and obtain these values.

### CALCULATE RAMP SLOPE

To identify the necessary slope for the ramp, it is necessary to have the information on the height to be exceeded  and the length of the ramp.

This type of ramp calculation is most used in situations where the ramp already exists and we need to identify the percentage of the slope.

Let's imagine a ramp where we have a length of 4 meters and the ramp has a height of 1.20 meters.

We then have the value of 1.20 multiplied by 100 (which results in 120) and by dividing the result by 4 we get the value of 30. Remember that the result must be expressed as a percentage, in this case we have 30%.

The value of 30% means that every 30cm, we gain 1 meter in height, so in 4 meters we win 1.20 meters.

With the result obtained, it is necessary to identify the function of the respective ramp and whether the dimensions meet the needs and the corresponding technical standards.

### CALCULATE LENGTH

In order to define the length for the ramp we need to know the inclination and height.

This type of ramp calculation is used when we need to identify which length is necessary for the construction of a ramp.

Let's imagine a vehicle ramp where we need a 15% slope and the ramp needs to reach a height of 1.60 meters.

We then have the value of 1.6 multiplied by 100 (which results in 160) and by dividing this value by 15 we have 10.66, which is the total length of the ramp.

The total length for this ramp is 10.66 meters, where it is also necessary to check if this dimension meets the applicable technical requirements and standards.

CALCULATE HEIGHT - To define the height required for the ramp, you must have length and inclination information.

This type of ramp calculation is used when we have the length and percentage of inclination information, allowing us to identify the height that the ramp will reach.

Let's imagine a ramp where we need to be 7 meters long and have a 10% slope, so we need to find out the height.

We then have the value of 7.00 multiplied by 10 (which results in 70) and by dividing the result by 100 we obtain the value of 0.70m.

In this case, we need to check if the result of 0.70 is sufficient for the ramp to meet the needs of the project.

If this is not enough, it will be necessary to change the length or percentage of inclination and redo the ramp calculation.

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### HOW TO CALCULATE A CURVE RAMP?

Curved ramps adopt the same calculation used in linear ramps, and the real concern is due to the radius that the curve will affect.

Ramps for pedestrians and wheelchair users, according to NBR 9050, must have a central radius of at least 3 meters.

For vehicles, we can use the AASTHO (American Association on State Highway and Transportation Officials) template, which is used by CET (Traffic Engineering Company).

In this template, the design is aimed at public roads, but it already offers us an overview of minimum dimensions that can be used in the design of a curved ramp.

### HOW TO MEASURE THE HEIGHT OF A RAMP?

A very common question is how to measure an existing ramp, especially when we need to check the slope percentage.

The measurement can be performed in a very simple way, you will only need a level, a nylon line and a measuring tape.

Attach the nylon line at the top of the ramp, so that it is stretched and with the aid of the level, check that it is straight.

Then you must measure the distance of 1 meter from the beginning of the ramp and finally make a vertical measurement, from the distance of 1 meter until it touches the ramp.

With that you will be able to obtain the slope percentage. For example, if the value is 12 cm, it means that for every 1 meter, 12 centimeters are overcome, that is, the ramp has a 12% inclination.

This process also makes it possible to measure the length, but it will be necessary to stretch the nylon line all the way along the ramp.

After making the measurement, it will be possible to analyze whether the ramp meets the needs of the work and the corresponding technical standardization.

## HOW TO CALCULATE A NBR 9050 RAMP?

The NBR 9050 is a regulatory standard, created by ABNT (Brazilian Association of Technical Standards) that defines all the technical aspects that must be observed to guarantee accessibility in buildings.

Degree 5.296 regulates the promotion of accessibility in buildings, where non-compliance is the responsibility of the professional who developed the project, implying a fine.

Check below what is the impact of the NBR 9050 in relation to the ramp calculation.

### HOW TO CALCULATE AN AFFORDABLE RAMP?

A ramp that meets the accessibility standard uses the same calculations that were presented here, however it must obey the slope limits and a maximum number of ramp segments, according to the reference table.

The slope percentage of the ramp should be between 5% and 8.33%, in addition to the need for intermediate levels for rest or change of direction.

In exceptional cases, when the possibilities that meet the ramp design table have been exhausted, it is possible to adopt another table, which has a greater limitation on the number of ramp segments.

In general, the impact we have on the design of an accessible ramp is that the percentage of inclination is small, which consequently significantly increases the length of the ramp, occupying a considerable space in your work.

## CONCLUSION

A ramp is an architectural element that must guarantee the safety of use, meeting technical requirements and also the corresponding legislation, so it is essential that it is correctly calculated.

Every architectural professional must know not only how to calculate but also how to adapt the ramp to the space available within the project, defining the most efficient route, whether linear or curved.

And a good project in addition to a correctly sized ramp needs to use quality blocks, so get ahead using the Block Revit family library, which has a huge catalog with weekly updates!

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### The author of the article

Luis André
Master of architecture, product designer and professor. Sharing professional content from leading architectural software for 10 years. # Revit Families

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