(01:16) Spoken Plainly
(02:51) When Is Concrete Used?
(04:15) 3D Printing vs. Ready-Mix?
(05:15) So It's The Automation?
(06:22) Who Can Tell Me Why To Print Homes With Concrete?
I've been chewing on 3D concrete printing (3DCP) technology and the Constru-Tech startups that want to commercialize it since before we started Foundamental in 2019, particularly 3DCP's role in residential construction. It's not that I have a strong thesis for it – the opposite. I'm genuinely confused about why it would have a category-leading role in low-rise or even mid-rise homes.
Spoken plainly
Picture your average single-family home. Whether it's in the US, Europe, or anywhere else, the basic structure is familiar. Traditionally, these are built using stick framing or large cinder blocks. Now, 3DCP aims to replicate this exact same design by promising to build the walls with solid concrete. But here's where I scratch my head – why?
Personal note: I am not advocating against building your home with concrete. My custom German home has two opposing exterior walls of solid 20cm concrete at 15m long and 12m tall ready-mix poured. The remaining walls are wood-framed. I get the benefits of concrete. Which is exactly why I am confused by 3DCP and concrete for volume residential applications. Which brings me to ...
When is concrete used ?
Concrete is the most used material on Earth after water. It's everywhere, for very good reasons. We cannot re-create the real world without concrete. Get that out of your head.
But every solution needs to fit a problem. A hammer looking for a nail is rarely a good thing.
And concrete's strengths really shine in two scenarios:
- Large surface and high-volume areas, and/or
- High structural integrity needs
Think massive projects like tunnels, highways, bridges, airports, stadiums, high-rise buildings (even road surfaces in many countries are built with concrete over asphalt for the reason of large surface area/volume).
Concrete is rarely the go-to for small surface areas with low structural requirements – exactly what 50%+ of homes are, and where 3DCP is being applied by almost anyone over the world right now. This is confusing me.
3D printing vs. ready-mix ?
Ready-mix concrete is a well-oiled machine in the construction world. It's mixed off-site, delivered by truck, and poured using gravity. While it's labor-intensive (formwork plus placement), it's hard to beat for large-scale applications. I'm struggling to see how 3DCP could outperform this method in those scenarios.
So it's the automation ?
Maybe this is the argument made by proponents of 3DCP technology for residential: Building a 1,500 sq ft home takes 50-100 person-days just to put up the walls. 3DCP could eliminate large portions of that wall-build labor.
But so are on-site robots for stick framing or brick laying, which are already there by promising ConTech startups. So even when making this argument, I will have to make the case why the wall-building method of solid concrete walls for residential makes more sense than automating stick-built or stones with robot technology. Who can make that case for me?
Anyone claiming sustainability ?
Here's a big sticking point: Ask the experts, and they will confirm that 3DCP today requires 20% to 50% more cement than traditional ready-mix concrete. Yes, it might get incrementally better as recipes and printer heads improve further (a big promise made by 3DCP pioneers), but there are mechanical reasons why you need more binder in this method. Using some common numbers, we're talking about using ±400-500 kg of cement per cubic meter of 3DCP, compared to 350-400 kg in commonly used ready-mix. That's a significant increase, and it seems worse for sustainability in an industry already grappling with its environmental impact. Unless I am missing something here?
Help: Who can tell me why to print homes with concrete ?
I'm genuinely asking. I want to hear from the concrete-printing experts (I am not one of them). Why should 3DCP for residential be a thing? What am I missing on a first-principles basis? Grateful for anyone help me see the potential that's attracting so much funding (though concentrated to a few players) to this space. Is there a fundamental breakthrough lingering that could change the factors I am breaking down here?
I'm all ears (for the experts).