The key to 3D printed construction is a materials problem.

Standard desktop plastic 3D printing is so powerful because you can create nearly any shape in a single go, with only small temporary supports where necessary. It has become a ubiquitous technology that is used in countless industries nowadays from making toys to car parts and rockets. And as such, people are now also trying to use it for the $10 Trillion housing market which has been plagued with high prices for many years now. There are many reasons for the price of houses and apartment buildings, but certainly if they were both cheaper and faster to build it would help alleviate several of the major issues. Which is exactly what 3D printed construction aims to accomplish.

So what’s the deal, why hasn’t it taken off yet?

Simple answer: It’s hard. But why is it so hard? We are able to 3D print all sorts of materials from plastics to metals to concrete and even some ceramics and other earth based materials. The computing side is also a solved problem as it can mostly be taken from other 3D printing technology. It also has plenty of funding and man power behind it.

Nearly all current 3D printed construction only uses 3D printing for walls and possibly the bottom floor, but intermediate floors and roofs are seldom printed. (Some roofs can be printed in a dome shape, but this really doesn’t work for intermediate floors). As a result they end up using some other technology for the floors often standard stick construction. Having to mix multiple different technologies like this ends up complicating the entire process and cancelling nearly all gains gotten from 3D printing.

So why don’t they just print intermediate floors too?

Seems like an obvious solution and it is. The issue is with the materials used for 3D printing houses. Standard desktop plastic 3D printers are able to print horizontally because the plastic cools really quickly and is able to hold its weight over moderately sized patches and each consecutive layer is able to still partially melt the previous layer and fuse to it. This however is very different from how most materials used for houses operate.

Most 3D printed houses use some form of concrete that comes out kind of like a really thick toothpaste and begins to set over the course of roughly half an hour and takes several hours to fully set. This is a great speed to create walls since it sets fast enough to hold the weight of layers above it without collapsing while also being slow enough fuse to the neighboring layers since the setting is time, not heat based.

The issue is that this doesn’t allow for much horizontal printing as it would simply fall before it is able to set. Or alternatively if it set fast enough to hold its own weight, then you wouldn’t be able to fuse the next layer to it.

Okay, so why not use a different material that does allow for horizontal printing?

Well our options are mostly plastics and metals as both set quickly and are temperature based which allows for fusing to the next layer. But obviously neither plastic nor metal is a great option for building a house out of.

A house has pretty important needs in terms material requirements, ideally it is:

  • Strong i.e. load bearing, rigid (to a certain degree)
  • Inflammable (doesn’t melt)
  • Insoluble (doesn’t dissolve it water)
  • Insulating. Both thermally and electrically
  • Affordable

Bricks, concrete and similar materials are certainly strong, inflammable, insoluble, electrically insulating, and affordable. While its not super insulating, it does work as a large thermal mass which effectively works as an insulator.

While it checks all the boxes for a house, because it’s slow to set it can’t be used for horizontal 3D printing. And materials that are able to be print horizontally don’t meet most of the criteria needed for a house.

Common metals like steel or aluminum, for example, are inflammable, insoluble, and can be strong enough with the right geometries, and importantly, they can be printed horizontally. However they aren’t thermally or electrically insulating, but those can be addressed with other materials easily. However, it is far from affordable and would be impractical to print an entire house out of metal

To really use 3D printing to revolutionize construction we need a material that fits most of the above that is also able to be printed horizontally.

So which materials might be promising?

This is where we enter the realm of speculation.

Personally, I believe that some sort of ceramic-like material is the most probable candidate. Ceramics are often very strong, are clay based and can be affordable, are thermally and electrically insulating, and can set quickly after being heated to a high temperature. I think the main issues would be making sure it’s not too brittle and ensuring that each layer fuses with the previous layer.

I think there are other possible materials possibly some sort of organic compound like wood, or a carbon foam, or even some sort of polymer. There’s lot of exciting materials research going on at the moment.

I think the key to making 3D printed construction something truly revolutionary is simply finding the right material, but I’d love to hear your thoughts.

A note on geometry:

I also think good strides could be made with current 3D printed concrete if we rethink house geometries. We should be able to print concrete spheres, so we could make houses out of room sized spheres packed together.

The bottom third or so of the sphere could be filled with appliances, storage, electrical, plumbing, etc… with an internal support system for a floor above. The top 2/3rds would be livable space. This way the entire structure of the house could be printed and would just need smaller components to be inserted afterwards, which would be much more efficient (cost wise) to produce, ship, and construct.

Other circle-based shapes also work, such as tubes and toruses. This could lead to some fascinating architectural styles that I’m sure some enterprising architect will take on eventually.