How to Make Foam Concrete Blocks

Co-authored by Mike Holmes Jr.

Last Updated: October 2, 2025

Foam concrete, also known as foamed concrete, or 'foamcrete', is a versatile cement based and porous lightweight building material that can be used for a wide range of building applications around your home. Depending on the job, you can use foam concrete for applications such as partition walls, void filler, and thermal insulation for walls and roofs.^{[1]
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Expert Source

Mike Holmes Jr.
General Contractor and Carpenter

Expert Interview} By following these simple steps, you can make your own concrete blocks for whatever outdoor home projects you desire.

1

Prepare the materials.

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The needed supplies include sand, water, block molds, gloves, and safety glasses. Do not worry if you do not have a cement mixer, as it can be substituted by a wheelbarrow.

2

Calculate the amount of materials you'll need.

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Depending on the nature of your project, ensure you are not making too much or too little.

3

Assemble your mixer.

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If you do not have a cement mixer, you can use a power drill with an attached paint mixer to mix materials in your wheelbarrow.

4

Prepare the mixture.

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Add 5 gallons of water to your cement mixer or wheelbarrow. Then, add the cement mix. For best mixing results, add the first half of your 94lb bag of concrete mix to your mixer or wheelbarrow. Mix until the cement is even throughout the whole thing and then add the last half of the bag. Once thoroughly mixed, prepare to add sand.

5

Add sand to the mixture.

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Sand dictates the weight and firmness of your blocks. For a lightweight result, you can use 1 bucket of sand, or for a stronger result, you can use 2 buckets of sand. Once the sand has been thoroughly mixed, prepare to add your perlite.

6

Add perlite to the mixture.

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Add one 5 gallon bucket of perlite to your mix first. Perlite will absorb the water in the mixture and thicken your mix. Depending on how thick you want your mixture, add anywhere from 5 to 25 gallons of perlite. Once you’ve reached the desired thickness, prepare to fill your block molds.

7

Fill the block molds.

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Ensure that you are doing so on a leveled surface. Pour your foam cement mixture into the molds. If the molds are small, pour the cement mix into a wheelbarrow and fill the molds with your shovel. For best drying results, cover the molds with plastic wrap.

8

Allow the molds to dry.

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Foam concrete blocks take about 24 hours to dry before they are ready to be removed from the molds.^{[2]
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Expert Source

Mike Holmes Jr.
General Contractor and Carpenter

Expert Interview}

9

Remove the blocks from the molds.

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Be careful when doing so - they still need time to properly cure. Refer to your cement mix bag for expected cure times.^{[3]
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Expert Source

Mike Holmes Jr.
General Contractor and Carpenter

Expert Interview} Now all that's left to do is build your desired project.

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Question

Can I replace perlite with another material?

Community Answer

You can use beads of Styrofoam. Gather Styrofoam and use a cheese grater to break up the Styrofoam to have loose beads of Styrofoam.

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