Understand the Cantilever Beam Formula & Its Calculation Ste

The cantilever beam formula is often mentioned in the world of building construction, but for laypeople, this term remains unfamiliar.

In fact, examples of cantilever beam applications are easy to find in everyday life, especially in houses and shop houses, where the structure appears to protrude and is supported on only one side.

If you want to understand how it works as well as the calculation steps, read the full explanation in this article.

What Is a Cantilever Beam?

A cantilever is a beam construction that is supported only at one end, while the other end is free without support. Since it is supported at only one point, the reaction occurs only at that point.

A cantilever beam bears loads at the free end or along the unsupported section, with the top of the beam experiencing tensile stress and the bottom undergoing compressive stress.

Once you understand the concept, you can learn about the advantages and disadvantages of cantilevers in residential construction.

Minimum Height of a Cantilever Beam

According to Table 9.5(a) of SNI 2847-2013, the minimum height of a cantilever beam without deflection calculation is l/8, with l being the span of the beam. The span is measured from the face of the column to the end of the beam, so for a 3-meter span, the beam height is 375 mm.

This means that the height of a cantilever beam can be less than l/8, but deflection must still be considered. It is recommended to follow this regulation, unless there are special requirements from the architect that necessitate a lower beam.

Cantilever Beam Formula

Determining a safe cantilever length is important for use in buildings. Each beam has its own dimensions and load capacity, so the length cannot be arbitrarily specified.

If the planning is incorrect, the beam can experience twisting or excessive deflection. Here is a quick guide to determine the cantilever length according to the type of load to ensure it remains safe and comfortable to use:

1. Formula for Not Too Heavy Loads

Cantilever length = 1/3 × (Span length + Cantilever field length)

Span length is the distance between two columns, while L is the sum of the span length and the cantilever field length.

For example, if the distance between columns is 2 meters and the cantilever field length is 1 meter, then the cantilever beam length is calculated as:

1/3 × (2 m + 1 m) = 1 meter.

This calculation is an assumption to facilitate initial planning and should not be used as an official reference. Due to its structural characteristics, a cantilever beam is not designed to bear very heavy loads.

Therefore, the covering above it should preferably be light, and heavy loads should not be placed on the free end of the beam. This approach helps maintain the stability and safety of your home's construction.

2. Formula for Brick Walls on Top of Free Ends

If the free end of a cantilever beam has to support a brick wall, there are two options; increase the cross-sectional area of the beam or shorten the cantilever length to:

1/5 × L (Span length + Cantilever length).

The span length is the distance between two columns, while L is the sum of the span length and the cantilever length.

For example, if the total L = 3 meters (2 m span + 1 m cantilever), the allowed cantilever length is only 0.6 meters or 60 cm.

Cantilever beams are very useful for expanding a space without adding columns. Proper planning of size and dimensions makes the structure safer, more comfortable, and cost-effective.

On the other hand, if planning is poor, a cantilever beam may require repairs due to safety concerns, and excessive deflection will reduce occupant comfort.

Advantages of Cantilever Beams

Cantilever beams offer many advantages, ranging from enhancing aesthetic appeal to adding space without additional foundations to saving construction materials.

Additionally, cantilevers are suitable for steep locations, allowing the house to remain functional and appear dramatic. Here are some of the main advantages of using cantilevers:

1. Suitable for Steep Locations

Cantilever construction is ideal for houses built on steep sites, such as hills, mountains, or coastal areas. Besides being safe, the building also looks dramatic and visually striking.

2. More Aesthetic House Design

Cantilever structures make the house design more unique and attractive, both in the interior and exterior. Their application creates a sense of more spacious and functional rooms.

In addition to enhancing aesthetics, cantilevers maximize the use of space. That way, the house looks modern and comfortable while remaining efficient in its layout.

3. Adding Space Without Additional Foundation

Cantilevers allow the addition of new areas without requiring a foundation, for example, for a balcony or an extra room. This way, you can maximize the limited space in the house.

4. Saving Construction Materials

A cantilever requires only one side as a support, making material use more efficient. Compared with structures with two supports, material costs can be lower.

This design helps reduce the use of concrete and steel without compromising structural integrity. Thus, cantilevers become a practical and economical structural solution.

Disadvantages of Cantilever Beams

On the other hand, cantilevers also have some drawbacks. Therefore, before deciding to use a cantilever, it is also important to understand its disadvantages.

In addition to requiring precise calculations by experts, cantilevers require a strong foundation and incur higher construction costs. Here are some things you should consider before implementing it:

1. Relatively Higher Costs

Although cantilevers can be more economical in terms of materials since part of the structure is suspended and does not require 100% foundation, costs can increase because you have to pay experts to design and execute it.

2. Strong Foundation Required

To support a cantilever, a strong foundation is essential. The type and size of the foundation must be adjusted to the site's soil conditions, at a minimum, by using a chicken claw foundation for a cantilever span of about 1–1.5 meters.

3. Must Be Designed by an Expert

Cantilever beams must be designed by a professional so that their size and strength match the calculations. Accurate calculations ensure that the beam can safely support the load.

If miscalculated, the cantilever is at risk of failing to support the load and sustaining damage. Therefore, expert input is crucial to the planning of this structure.

That is the explanation regarding the formula and steps for calculating cantilever beams for buildings. In its execution, precision is very important to ensure the structure remains safe and functions as intended.

In addition to accurate calculations, material selection is critical, especially for cement, the primary material in many construction projects. For a more reliable quality, you can rely on Semen Merah Putih.

One of its flagship products is Semen Merah Putih Watershield, a super premium multipurpose cement with water-repellent technology that provides optimal protection against seepage from the outside, inside, and from the ground or capillary water.

This product is suitable for a variety of structural and non-structural needs, including beam work and other concrete elements, due to its high adhesion and durability.

So, to support strong and long-lasting construction, trust your project to Semen Merah Putih Watershield.

If you need more information, do not hesitate to contact us and consult your construction needs today!

Understand the Cantilever Beam Formula & Its Calculation Steps