Structural safety is a huge concern for homeowners when the time comes time for their once-in-a-lifetime purchase. It directly affects durability and strength and is a good metric to analyze the lifespan of a house.
3D printed houses make use of unconventional construction techniques that can raise concerns regarding structural safety. It is perfectly fine to be skeptical as the technology is new and is yet to stand the test of time. However, the early adopters have shown very promising results!
So, is a 3D printed home structurally safe? Yes, a 3D-printed house is structurally safe. 3D printed houses are structurally sound and strong, as much as (or in some cases, even more than) their conventionally built counterparts. These houses incorporate a variety of technologies into their construction process that makes them durable and long-lasting.
These claims are supported by extensive peer-reviewed research that has been carried out in recent years. Scientists and engineers have been hard at work trying to test the strength of 3D printed houses.
Their results indicate that 3D printed houses match (and in certain cases outperform) their conventionally built steel or timber counterparts (source). Rest assured, if your house in the future is a 3D printed one, you would not need to worry about its structural rigidity.
You may also get informed about the fire safety of printed houses in Are 3D printed houses fireproof? and Are 3D Printed Houses Hurricane Proof? and about costs in How much does a 3D printed house cost?
Not only are they safe, the 3D print market is also growing, check out our analysis in Is the 3D printed housing market stable?
What makes a 3D printed house structurally safe?
Let’s talk about what technologies do 3D printed houses use that make them durable. Several factors contribute to the structural strength of a 3D printed house.
The material used for construction perhaps plays the greatest role in determining the viability of a 3D printed house. It can range from concrete, wood, and even clay (For more on this, we recommend that you check out our post “Can You Make a 3D Printed House out Of Clay!”).
The most common material being utilized right now is concrete. It has high flowability and short setting times, which makes it perfect for 3D printing applications.
Concrete also gains the majority of its strength within a short time after it sets, which helps improve the rigidity of the structure that is printed with it. For more on 3d printed houses, check out our post Will 3d Printed Houses Stand the Test of Time? Durability/ Strength/ Sustainability !
Another important factor is the design (and by extension, the construction process) of the house. 3D printing works on the principle of extrusion, by which material is layered continuously to erect a 3-dimensional structure.
This layering process is heavily influenced by the design of the house. It can be a dome shape, which for the most part, is free-standing and can support its own weight.
Or it can be a straight-walled house with a roof. In that case, reinforcements may be needed to strengthen the individual structural members of the house (we’ll talk more about that later).
Quite often, a hybrid of conventional construction techniques and 3D printing is used to build. This accounts for cost savings and takes care of specialized operations that the printhead might not be able to execute.
Also check out “Do 3D Printed Houses Have a Foundation? Materials and Methods“
This human input also acts as an additional layer of accountability (pun intended) and allows the workers to ensure that the structural requirements of the house are up to par.
If you are still unconvinced about the durability of a 3D printed house, go check this article, covering different aspects of their durability and life span.
Also, for more on Earthquakes and 3d printed structures, check out our post titled “Can 3D Printed House Withstand Earthquakes? Design and Foundation Limitations“
How does the layering process affect the strength of 3D printed houses?
The extrusion process works such that the printhead of the 3D printer moves across the perimeter and lays down a stream of concrete onto the surface.
The concrete used in the process needs to have many qualities to be effective. Most importantly, it needs to dry and strengthen quickly so that it can support the weight of the layers on top of it.
This is achieved by adding accelerators and superplasticizers into the concrete. Both additives help the concrete set quicker and gain the required strength before the next layer is put on top of it.
Other additives may also be added to increase the resistance of the concrete to corrosion and humidity changes. In addition and for other applications, the effects of layering can be mitigated in specific applications such as swimming pools, as explained here.
Apart from that, the process of layering is constantly adjusted to account for the gap between layers. This ensures that the wall (or the structural member) has enough strength to carry its weight and the weight of structures being built on top of it.
It may seem counter-intuitive, but concrete (despite its layered form) is extremely resilient and early adoptions of additive manufacturing (the technology behind 3D printing) have shown to be strong and durable.
These structures have been rigorously tested and have proven to be up to safety standards in many building codes across the world. (You can find more details about that at the end of the article)
Another concern is cracking in the layers of the concrete because of uneven drying. Rebar can help mitigate that problem. Its use and benefits will be discussed in the following paragraphs.
How does rebar help strengthen a 3D printed house?
Reinforcement (or rebar) plays a significant role in structurally strengthening a house. It pairs up with concrete and gives it the required tensile strength to make it (reinforced concrete) one of the most durable building materials.
The issue lies in incorporating conventional rebar into the 3D construction process. Since it is a layering process, there cannot be any obstructions in the pathway of the printhead, and that makes incorporating conventional rebar a challenge.
There have been several innovations in the 3D printing industry to overcome that challenge and several new techniques have been developed that allow the integration of rebar into 3D construction.
Smart Dynamic Casting (developed by researchers at ETH, Zurich) is one such innovation that has allowed rebar to be used in the 3D construction process.
Substitutes for conventional rebar have also surfaced, and although they have not been widely implemented, they carry great potential. Examples of these rebar alternatives include fiberglass, meshes, and basalt rebar among others. (source)
Most of these reinforcements are made part of the mixture unlike conventional steel bars and they act like micro reinforcers, providing strength on a localized scale in the structural members.
You can find more detail about the use of rebar in 3D printed houses in Do 3D Printed Houses Use Rebar? where we go into much greater detail on the topic and also on height issues in How Tall Can You Build a 3 D Printed House?
Do 3D printed houses comply with the building codes?
One of the best ways of ensuring that a house is structurally sound is by looking up if it follows and passes the building codes of the local construction authority.
Developers must undergo testing to get their housing projects approved and this ensures that a certain standard of safety is reached without cutting corners.
The same metric applies to 3D printed houses and slowly developers have been getting approvals from local building authorities.
In the US, developers like ICON and Apis Cor have been getting steady approvals for their construction projects by local building authorities. This implies that they comply with all the necessary safety standards. (source)
However, there is a lot of work still to be done, as regulators need to keep up with the rapid innovations in the construction industry. This will act as a layer of accountability, which will minimize the risks associated with unsafe construction practices. Other progressions are also related to Mechanical and Plumbing components which are covered in Could A House Be 3D Print To Include Plumbing and Electrical Components?
Similarly, Underwriters Laboratories (a global safety certification company) published an investigation outline that was referenced in the IRC. This document underlines the procedures through which standards of safety and strength must be analyzed for 3D printed houses. (source)
Local building authorities (like the ones in the US) are already adopting these findings and making use of them in their testing and compliance ratings.
This is a positive trend for the industry as it not only ensures safety but also helps bring 3D construction out of a legal grey area.
Extensive cross-disciplinary research has shown 3D printed houses to be viable in many conditions and environments. This goes to show that 3D printed houses are a suitable alternative for future construction of households.
Developers all over the world have built 3D printed houses in different conditions, with various materials and multiple designs. This goes to show how resilient technology is.
You can find an extensive list of 3D printed houses (of various shapes and sizes) in Are 3D Printed Houses Affordable?.
There is still a lot to be done for 3D printed houses to gain market-wide acceptability. However, if innovation keeps happening at the current pace, it won’t be long before 3D construction finds its place in the next generation of houses.