How do you calculate formwork for a concrete slab?

22 Jul.,2024

 

How to Calculate Formwork?

Formwork is an essential component of any construction project, as it provides support and shape to the concrete structure. However, it can be difficult to calculate the amount of formwork required for each component of the project. In this article, we will provide you with a guide on how to calculate formwork for footing, slab, beam, columns, and wall. 

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How to calculate formwork for footing?


The first step in calculating formwork for footing is to measure the dimensions of the footing. The width and length of the footing are multiplied to determine the area in square feet. Then the depth of the footing is measured and added to the height of the side forms to determine the total height of the form. Finally, the total height is multiplied by the perimeter of the footing to determine the total formwork needed in square feet.


How to calculate formwork for slab?


To calculate formwork for a slab, you need to measure the length and width of the slab in feet. Then, multiply these dimensions together to calculate the area of the slab. Add the thickness of the slab to the height of the side forms to calculate the total form height. Finally, multiply the total form height by the perimeter of the slab to determine the total formwork required.


How to calculate formwork for beam?


To calculate formwork for a beam, you need to measure the length and width of the beam in feet. Then, multiply these dimensions together to calculate the area of the beam. Add the height of the side forms to the height of the beam to calculate the total form height. Finally, multiply the total form height by the perimeter of the beam to determine the total formwork needed. And the concrete beam formwork has many types.


How to calculate formwork for columns?


Calculating formwork for a column requires measuring the diameter and height of the column in feet. Next, multiply the diameter squared by pi (3.14) to obtain the area of the column. Add the height of the side forms to the height of the column to determine the total form height. Finally, multiply the total form height by the perimeter of the column to determine the total formwork required.


How to calculate formwork for wall?


To calculate formwork for a wall, you need to measure the length and height of the wall in feet. Then, multiply the length and height to obtain the area of the wall. Finally, add the thickness of the wall to the height of the side forms to calculate the total form height. Multiply the total form height by the perimeter of the wall to determine the total formwork needed.


Calculating formwork for each part of the construction project is essential in determining the materials and costs required for a successful project. By following the guidelines provided for footing, slab, beam, column, and wall, construction professionals can calculate the exact formwork required for each component. With the right calculations and materials, construction projects can be completed safely, accurately, and on time. At TECON, one of the leading specialists in formwork and scaffolding engineering, we provide high-quality formwork solutions to help construction professionals achieve these goals.

How To Calculate & Measure Formwork

How to calculate formwork for columns

Formwork is needed to support vertical concrete forms such as columns, pillars, posts, shafts, struts and walls.

For square or rectangular forms, calculate the perimeter of the base and multiply it by the height.

For round or elliptical columns, calculate the area by multiplying the circumference (2πr) by the height.

If you're making any home improvements involving concrete, you're going to need formwork to hold it in place while it hardens. Knowing how to calculate formwork will make sure you order enough materials and can budget your project more accurately.

Follow this guide to find out how to measure formwork you need. If you don't want to calculate formwork yourself, you can hire a professional formwork estimator to take care of it.

Find out more: What Is Formwork?

How to measure formwork

While you'll be ordering concrete by volume, formwork is measured by area. Specifically, the area that will actually be in contact with the concrete. This means calculations will be in square meters (or square millimetres if more accuracy is needed).

To measure the area of formwork needed to support your concrete installation, multiply the perimeter or circumference by the length/height of the structure. Each side of concrete will need its own formwork calculation and more complex or irregular shapes will have more complex calculations.

How to calculate formwork for slabs

If you're laying a concrete path, driveway, foundations or other base or flat surface, you only need to know how to calculate formwork area.

· For simple square and rectangular forms, simply multiply length x width to know how much formwork you need.

· For a circular base, multiply the square of the radius by pi (πr²).

· For irregular shapes, break these down into simpler squares and rectangles and add up the total surface area.

How to calculate formwork for columns, walls and posts

Formwork is needed to support vertical concrete forms such as columns, pillars, posts, shafts, struts and walls.

· For square or rectangular forms, calculate the perimeter of the base and multiply it by the height.

· For round or elliptical columns, calculate the area by multiplying the circumference (2πr) by the height.

If you're making formwork yourself, plywood supported by a lumber frame is the most economical option, but this won't be an option for round or irregularly shaped columns. These require metal formwork, which may need to be installed by a professional.

How to calculate formwork for beams and girders

Formwork for concrete beams, girders and other horizontal forms should only be fitted on three sides, with shuttering supporting the two vertical sides and the bottom face. The top face should be left exposed.

Add the lengths of the three sides, then multiply by the span of the beam to calculate the formwork area needed.

Square and rectangular beams and girders may be made from plywood supported by lumber or metal. Round formwork should be made from metal.

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Formwork calculation example

For an example of how to calculate formwork for columns, let's say you need to estimate formwork for square concrete posts measuring 0.2m in length, 0.2m in width and 3.0m in height. The formwork uses plywood shuttering measuring 1.2m x 2.4m supported by a lumber frame.

To estimate how much plywood formwork you need to buy, you need to multiply the perimeter by the height to get the surface area needed for one column, then multiply this by the number of columns you need. Finally, you need to estimate how much plywood this would take.

Step 1: Calculate the concrete perimeter

Calculate the perimeter by adding the lengths of the four sides (a, b, c, d) and adding an extra 0.2m for overlapping of joints.

In this example, the calculation is:

 

Perimeter = a + b + c + d + 0.20

Perimeter = 0.2 + 0.2 + 0.2 + 0.2 + 0.2

Perimeter = 1.0m

 

Step 2: Calculate the concrete surface area

Multiply the perimeter by the height of the column to get the surface area of the plywood shuttering.

 

Area = Perimeter x height

Area = 1.0 x 3.0

Area = 3.0m²

 

Step 3: Multiply by the number of columns

Let's say you're building 8 columns. The total area of all the concrete columns will be:

 

Total area = Area x number of columns

Total area = 3.0 x 8

Total area = 24m²

 

Step 4: Calculate the plywood surface area

Calculate the surface area of the size of plywood you're using. This example uses 1.2m x 2.4m plywood.

 

Plywood area = length x width

Plywood area = 1.2 x 2.4

Plywood area = 2.88m²

 

Step 5: Calculate how much plywood is needed

Divide the total concrete surface area by the surface area of one piece of plywood. This tells you how much plywood you need to buy.

 

Plywood needed = Total area / Plywood area

Plywood needed = 24 / 2.88

Plywood needed = 8.333

 

This means you'll need to buy 9 pieces of 1.2m x 2.4m plywood along with suitable falsework for support.

 

Common issues with formwork measurements

The difficulty of how to calculate formwork largely depends on the shape of the concrete form you're supporting. While a square or rectangular form will be straightforward to calculate and suitable for modular formwork, round or irregular forms may be more challenging and needs to be custom made.

If formwork can be reused on the same project or on future projects, this will lower the overall cost. However, the measurements need to be precisely the same each time. Metal formwork can be reused multiple times, but wooden formwork may not stand up to reuse, especially over long periods.


Find out more: How to Remove Formwork

For more concrete slab formworkinformation, please contact us. We will provide professional answers.