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What happens when you put hemp into a structural brick?

Will Stewart, director and co-owner of Natural Brick, joins us to unpack how his team is rethinking one of the most familiar building products around, from what goes into the mix to how it performs once it hits the wall.

Natural Brick’s current brick uses hemp grown in NSW, making up around 45–50% of the mix by volume. Rather than being kiln-fired, the bricks are naturally cured using solar heat over an eight-week process. The result is a load-bearing single-skin brick that has achieved an unconfined compressive strength of more than 11 MPa, with recent testing closer to 15 MPa, and an impressive 180/180/180 fire resistance result.

Will gets into the practical details builders and architects actually want to know: how the brick handles moisture, salt attack and weathering, why it needs to be laid dry, what the long curing time means for project planning, and where the current carbon assessments fall short.

We also get into the more experimental side of Natural Brick, from algae-based bricks and bricks made from construction waste to furniture made from recycled stone and even a bone terrazzo table.

And then there’s the custom work. Natural Brick has developed an in-house mould-making process that can bring a custom curved brick mould down from a typical five-figure setup to around $1,200, while allowing moulds to be reused across projects.

It’s a conversation about what happens when you take a conventional building product, question how it’s made, and start looking at waste, materials, manufacturing and performance differently.

EPISODE HIGHLIGHTS

• How Natural Brick makes a structural brick using around 45–50% hemp by volume
• Why Natural Brick uses solar curing instead of kiln firing or mechanical curing
• The testing behind the product, including 11+ MPa compressive strength and a 180/180/180 fire resistance result
• What builders need to know about moisture, durability, weathering and laying the bricks
• How custom curved brick moulds can be made for around $1,200 rather than a typical five-figure setup
• The reality of measuring embodied carbon, including the limitations of current assessment processes
• What Natural Brick is experimenting with next, including algae and construction-waste bricks
• Inside the furniture studio, where recycled stone, industrial by-products and even animal bone become new materials

CHAPTERS

0:00 - Meet Will Stewart and how Natural Brick began
1:58 - Building schools in Kenya, and what it taught him
6:10 - Back to bricks: why mud bricks didn't work
7:36 - The Lutyens brick and its long format
9:50 - How the brick is actually made
12:14 - Switching to hemp, and why it works better
13:49 - Solar curing instead of a kiln
14:29 - Inside the mix: hemp, sand, cement, fly ash, pigment
17:27 - The carbon numbers and the Think Brick study
20:10 - Where carbon assessment falls short
21:32 - Compressive strength and the 180/180/180 fire result
23:01 - Vapour permeability, moisture and laying dry
24:54 - Thermal performance and R-value
27:06 - R&D: the algae brick and construction-waste bricks
36:59 - A curved apartment project, and reusing moulds
42:19 - Weathering, sealing and cleaning without acid
46:38 - What's next, and the furniture side
54:39 - The biggest constraint, and getting to low carbon
56:05 - Quickfire

ABOUT THE GUEST

Will Stewart is director and co-owner of Natural Brick, a New South Wales maker of handmade, hemp-based masonry. He came to bricks after around six years building schools in Kenya and Uganda, then a stint in beverage sales, and now runs the business with two co-owners out of a solar-powered factory in Warragamba, at the foot of the Blue Mountains.

LEARN MORE
Natural Brick: https://naturalbrick.com.au
Sustainable Builders Alliance (SBA): https://www.thesba.com.au

BROUGHT TO YOU BY
Sustainable Builders Alliance (SBA): https://www.thesba.com.au