Prior to tech, I primary worked in construction during and right out of high school.

Cast-in-place concrete dwellings have never caught on despite it making a tremendous amount of economic sense. While it has a foothold in the market for specific applications (basements, retaining walls, commercial buildings, etc), a concrete house form in-a-box poses some logistical challenges and human ones.

First, the vision here was to be able to drop a form and creates a single pour/unibody structure (like injection molded plastic). That is very difficult to do and most concrete work is done in multiple stages for this reason. The main challenge is the creation a form that is sufficiently supported on the inside to create the “void” of the living space. You’re having, instead, to pour a slab, wait a sufficiently long time for it to cure enough to support weight, and do the walls and ceiling next.

The other logistical issue is internal reinforcement, which is what rebar is for. Concrete, as a building material, can really only resist compressive loads, which makes unaided concrete highly unsuitable for applications where there is a void underneath (in our home, for example, under a window frame, under a ceiling, or in infrastructure, as an overpass) However, by using iron-reinforced concrete, we can turn shear forces into compressive and by using pretensioned concrete (stretching of reinforcement cables prior to concrete pour), we turn tension into compression as those stretched steel wires want to return back to their original shape, it’s like an internal lasso keeping it together.

The last logistical challenge is installation of all utilities, which means in/under slab and wall piping (water supply lines, in floor heating, DWV, etc), electrical with conduit setup going to masonry boxes, outlets, switches, light fixtures.

The point here is, setting up for a concrete pour is not as simple as erecting forms. When the concrete pour is cured into a structure, it’s now a very inflexible material to work with and any wall penetration needs to be checked against blueprints, new electrical need to be run on the surface, leak repairs need to be done with very specialized equipment and a tunnel created under the dwelling, etc.

The other main problem is that people don’t want complete concrete homes. Without in-slab heating, it is a cold, hard, unforgiving material that allows for zero flexibility and repairs are a nightmare. Just like software, homes should be built with maintenance in mind because that’s the normal state in which it is worked on. Plus, it feels like a prison. At least it won’t burn down?

I have a lot of gripes with slab-on-grade construction[0] for this reason, and every dwelling I’ve built has had at least a crawl space, often a basement where everything is serviceable. The basement is usually CMU (concrete masonry units, aka cinder block), precast concrete (slabs trucked in), or, rarely, ICF (insulated concrete forms, basically in-place formwork with concrete in the middle of two pieces of foam insulation like an ice cream sandwich[1]).

I think there are some things we can learn from commercial buildings where you can have concrete skeletons[2][3] but large cut-outs where you can build walls. Inside the concrete pillars are PVC channels that let you thread wiring and plumbing, and other things through without having to do a concrete penetration. To built the house part, you effective put up wood frame walls in the voids or an aluminum-framed window installation (like a storefront assembly).

Side note: If you have ever wondered why you see basements in colder climates (and conversely more slab-on-grade in warmer ones) is because the bottom of your construction need to be situated under the frost line to prevent shifting caused by the ground freezing. So if you have to dig 4ft down anyway to reach that point, maybe just dig out a 5ft hole and install a basement instead, then your can have your home’s first/ground floor about 3-5 feet elevated. Slabs made to handle the shifting of ground due to freezing, liquefaction, or unstable building surfaces are called “rafts” and are not used very often compared to other methods.

[0]: https://anchorfoundationrepair.net/blog/slab-foundation-how-...

[1]: https://images.finehomebuilding.com/app/uploads/2017/10/3011...

[2]: https://en.m.wikipedia.org/wiki/Concrete_frame

[3]: https://www.understandconstruction.com/concrete-frame-struct...