Two-bedroom house printed in 18 hours | Hacker News Reader

Two-bedroom house printed in 18 hours

cobod.com

31 pointsbelter74 comments

I curious how good the infrastructure -- the plumbing/electrical/network/appliance hookups -- are in this sort of thing, and how repairable the fixtures are. If I have to sledgehammer a wall out to replace a bad outlet, I think that would get pretty old pretty quick. Having built some boats, and having lived in an old abandoned boat through college (somehow getting the thing shipshape on undergrad money, although I took shortcuts that would curl my hair now) I can testify that the hull is the cheapest part of the boat. All the other stuff is the hard part. Houses are sort of like that, but a lot less critical than a boat hull at sea. The walls and roof are just chunks of stuff.

This is a good video about a real housing development (ie. not just a single demo house) that explains a lot of those infrastructure details: https://youtu.be/Y-4S7cdo3tY

The thing is a conventional framed walls go up just as fast, all the other finishing in both styles of building is where all the time is spent. In that video they still are using conventional trusses as well. If you have ever driven by a building site after the foundation is poured and dried. Then drive by in the next day or two often you see pretty much all the walls are framed and standing sometimes even have all their sheathing on the walls. It's the finish work and all the small details where all the time is spent.

When I look at robotics transformers like RT-1 I'm left scratching my head why nobody has tried to build a robot to apply grout/plaster. At some point robotics transformers will be so good that they could learn directly from human demonstrations.

I can imagine it wouldn't be to everyone's tastes, but I actually find the end results, especially the interior shots, quite pretty. A little like being wrapped in burlap or sisal twine. I almost expect it to be fibrous to the touch.

I like that the layers remain as evidence of its construction technique, much like the exposed beam ends on the outside of adobe houses, or the 2x4 board impressions left on the outside of some concrete facades.

If they can really get stuff done in 18 hours and the cost is as competitive as the article claims, then adding standard interior drywall and exterior cladding to make it look like a regular stick house shouldn't inflate the cost of the house too much. The time savings on labor, equipment rental, and other fixed costs might pay for it.

Building the walls of a concrete block house doesn't take much over 18 hours of labour either. You can't go up more than ~6 feet in a day because you need the bottom layers to gain strength before adding more on top, so you end up doing ~3 6 hour days.

This could be optimized further with things like block feeders/lifts to bring the blocks to the worker.

Yea honestly this is very similar to a building built from CMU and not adding siding or interior furring strips for drywall on a CMU build. Honestly, walls are one the faster things in building anyways. It's all the other finishing work where all the time is spent.

As usual for "3d printed house" stories, there's no mention of reinforcement. Is this just unreinforced concrete?

Or, you know, foundation.

Doesn't reinforced concrete have a lot of longevity problems? If the printing is limited to the walls, i.e no large suspended horizontal section, it seems better to stick to pure concrete from my non-expert understanding.

The climate may require using corrosion resistant rebar; most non-corrosion failure modes would happen with unreinforced OPC.

> Doesn't reinforced concrete have a lot of longevity problems?

Mostly near sources of (salt) water: put a roof on a house, and make sure you have slopes away from the structure, and it's not a large problem.

Or, instead of metal/steal rebar, you can use composite rebar:

* https://www.jlconline.com/how-to/foundations/composite-vs-st...

There's also fiber-reinforced concrete (which may not always be a replacement for rebar):

* https://en.wikipedia.org/wiki/Fiber-reinforced_concrete

I'd guess maybe fiber reinforcing?

It always strikes me as odd that we have housing crisis everywhere but these cheap 3D printed houses or ready-to-assemble houses from Amazon never took off. Does people find it off-putting to live in these? Or is it more of a regulation issue? Or land acquisition issue?

Land is the issue. And more specifically, land in a desirable location.

You're going to be surprised, but the solution to the housing crisis isn't 1-2 bedroom single family houses.

But just imagine... sprawling suburbs as far as the eye can see, all of them printed out by robots. The American Dream.

Now all we need is some robots to clear-cut all the useless vegetation that's occupying the land that these future wonder-developments will sit on.

It's a land acquisition issue due to zoning laws and stuff. For example, in the Bay Area, where houses are super expensive, it's just that there are limited numbers of houses and you essentially aren't allowed to build more (without having to jump through insane hoops). Meanwhile, there are huge tracts of land being wasted on low value things like empty parking lots.

Right next to my $1.85M San Jose single family house (1300 sq ft, built in 1959, very unremarkable), there's a plaza with a Dollar Tree that is almost always empty.

In comparison, a "Mobile Home" in the same area would only be $400k [1] , with similar house size and build quality. It's a lot cheaper because you don't own the land.

[1] https://www.zillow.com/san-jose-ca/mobile/

For more on zoning challenges, I'd suggest the book Arbirary Lines[1] by M. Nolan Grey; excellent overview of the history and problems.

[1]: https://islandpress.org/books/arbitrary-lines#desc

It is very often a zoning issue. "Manufactured" housing, which I'll use as a blanket term for anything not completely built on-site, is often equated with "mobile home" or trailers. In the U. S., at least, mobile homes have a stigma that carries over to manufactured housing. IOW, mobile homes are for poor people, and you're not poor, are you?

Consequentially, manufactured homes often have to be built in unincorporated areas which don't have zoning restrictions.

I don't think there's any of these 'solutions' beyond the demonstration phase yet. Also, these 3d printed homes are only 'printing' a relatively small fraction of the work required to create a home.

There are cheap housing options that already exist but they typically have a stigma. This 3d printed home is quoted as 3x more expensive by area than this existing option: https://www.claytonhomes.com/homes/21TRU28563RH/

This house is 80 square meters and cost 150,000€ to build. You can build a regular house of the same size in the US for the same, or less.

This is also true for a lot of the "kits": they're not particularly inexpensive for the floorspace (especially considering the labor needed), and often require a lot of finish work to be livable. If you have the land, manufactured / modular can end up being more cost effective and considerably quicker.

These strike me as schemes to mark up materials moreso than honest efforts to provide affordable housing.

I never understood it either. The 3D printed houses look like unfinished throwaway housing. The type you would build as a homeless shelter or refugee camp. When it is time to tear it down, you somehow reuse the concrete in the next house. That is the kind of impression or "vibe" these houses give me.

This is more a regulation issue, of course. But it's not the kind of regulation which one can call stupid, and repeal. There are objective conflict between people who already stored their savings in houses (directly, or indirectly) with many of those who want to get a house. Combined with the fact that those who already live within few desirable economic centers often want others to stay away.

The housing crisis is not universal. The last few decades saw a trend towards re-urbanization and re-centralization after the prior several decades favored flight from urban centers into sprawling suburbs.

That's culminated in excessive demand for housing in areas that are already heavily developed with existing structures and land-use, and pressure for demolition/reconstruction and rezoning for higher density, which is not easy to achieve.

Modular, manufactured, and kit homes are almost universally single family structures which don't do much for that problem. They have a place in ADU (accessory dwelling units) construction that marginally increases density in some neighborhoods or certain kinds of creative urban developments, but mostly just make it easier and cheaper to build out new land in those places that many currently don't see as desirable.

That said, in the big picture, continued innovation in that sector helps ready for the inevitable pendulum reversal as people recognize their urban centers as inaccessible and/or blighted and adopt a new vision of their own future. But that's not a "today" solution or really something that can be controlled very well at all.

It's a tech demo for its own sake. We've had cheap pre-fabricated homes for 70+ years in the US and they haven't solved the housing shortage either.

Housing shortages are always a city planning issue and the planning problem doesn't exist for every city independently either. If one city does something, then other cities may do the opposite and ruin the effort.

[deleted]

I've an idea for making this machine much cheaper.

Instead of a very expensive looking X-Y-Z gantry which looks like it needs a crane to erect and a pre-made concrete foundation, instead use 3 posts in a triangle.

Each post wouldn't be need to be set into the ground - it could be just placed on dirt. Each post is held out with guy-wires to weights (rather like a circus tent is held up), and inwards with cables to the top of the other posts. The whole lot could be light enough to put up by hand. The "weights" could be water bags which can be filled with a hose when put in place.

Then, from the top of each post you have a cable inwards to your 'print head'. The print head uses three winches to pull on these cables to get to anywhere in the x-y-z space.

Obviously, such a system will have flex and wobble - which isn't great if you need perfect alignment for building your house. Thats solved by using laser angle/distance sensors to surveyed markers around the base of the house, and a continuous feedback system, allowing any flex/wobble of the structure to be compensated for.

As a bonus, with 3 additional cables from the head to the towers and 3 extra motors (which can be cheap), you can get a 5 axis machine allowing the printing of non-flat layers, allowing overhangs, arches, sculptures, etc.

A plotter, basically!

As much as I can see why the company making these homes would not want to cover up the unique texture of the walls, I feel it somewhat hurts the appeal. If they put the extra effort into adding some drywall and making it virtually indistinguishable from other homes, everyone would likely focus on the time and cost savings.

All I can think of looking at those pictures is how ugly it looks.

If you screw some furring strips on the interior walls you could just run drywall over the top of those.

Or just plaster it.

Looking at the picture on that article. I have seen people conventional frame a house that size in 2 days. So basically as fast. The thing with these 3d printed houses is it does nothing about the finishing work. That is where most the time is spent in construction. Those floors, doors, trim, electrical, plumbing, the painted ceiling, the roof, flashing windows and doors, the landscaping ect... in that 3d printed house took much longer than 18 hours. Framing is one the fastest stages in building a house. So you just make walls slightly faster it's not going to really speed up building a house overall.

Like sure in these in pictures they forgo siding and drywall. But I will tell you inside the texture of that wall is going to collect dirt and dust overtime, and not everyone is gonna want a bumpy wall like that in every room. So avoiding some interior finish work like dry walling is not a given. Overall this does not speed up construction that much.

"With €150,000, it's possible for a young couple to have the home they've always dreamed of, in an area with good access and services"

Ahm ... is there a housing crisis in Europe as well? Because that price tag doesn't sound remarkably cheap to me.

This was posted recently (https://news.ycombinator.com/item?id=39980143), but didn't make the frontpage:

What Progress Has Icon Made on 3D-Printed Homes?

https://www.construction-physics.com/p/what-progress-has-ico...

As with all things related to home construction, there are thousands of different tradeoffs. Good to see some organizations are still exploring if 3D printing can make sense.

How long have we been hearing about 3-D printed homes? Years. Many years. None have ever gone beyond the demonstration phase into widespread adoption.

This sort of thing reminds of all the wild claims about a new revolutionary battery storage or revolutionary data storage solution on a new medium. None of those things have come to pass.

It is OK to keep trying. But, it is not newsworthy when the similar thing has been demonstrated 110 times before, in a controlled environment.

I'm a big fan of the oft-misunderstood[1] Brutalism. And this reminds me of that.

Extrudalism.

[1] https://www.iheart.com/podcast/105-stuff-you-should-know-269...

Nothing more beautiful than wet, dirty and spalling concrete.

https://en.m.wikipedia.org/wiki/Prentice_Women%27s_Hospital#...

But how long did the printer take to set up?

One of the implementations I’ve seen is just a pretty much regular truck with a crane like arm that contains the concrete hose and pump[0]. So not long, I take it.

[0] https://www.bft-international.com/imgs/1/5/3/0/5/1/2/11_1_Sc...

There aren’t many details but am I correct in understanding that the foundation and finishes still have to be done through traditional methods? Only the walls are printed? Does that really save much compared to pouring concrete?

Hit it with some surface treatment and some paint and you can start thinking Art Deco.

I have dust allergies and those inner walls would make my life miserable. I think the Cobod printer, which happens to be designed by a former colleague of mine, should be able to produce a better result given a little more time.

- But how many floors high is the system able to build?

(and at what price?)

Locations that would benefit from (more) affordable construction are high-density.

[deleted]

PC LOAD CEMENT?

What about the plumbing and electrical?

This is probably why the text of the article mentions that it actually took two months for the house to be finished. The 18 hours was just the framing, essentially.

That's still 1/14 the time. Production framers in the US can usually frame a 2-story 2500 square foot house in less than 2 weeks today.

The print time needs to be added to the printer setup time. Something that big will have non-trivial effort to get on site and set up and then tear down after the print.

If that takes six days and the print takes a day then the printed house takes half the time of traditional framing. An improvement but not a revolution.

Concrete has additional issues though with weight being significant. Soil that can support a wood framed house can't necessarily support the same size concrete house. At least not without additional compaction. That just adds to pre-construction time and permitting.

If it was 1 story house of that size less than week to get it framed from a decent crew. The pictured house here was a single story house. Also this 3d print for multi-story building would probably not be much faster since unless both the first and second floor shared the same interior wall layout they would have to stop and make a floor for the interior of the second floor. Plus the weight of concrete means those second floor interior walls would be conventional framed anyways. Unless you want to make the floor extremely expensive to carry that kind of load...

As someone who isn't in the industry, that raises the question - is framing usually the choke-point? They say it took half the time, so is that other half the time all framing? Or is there other factors at play here?

After some recent experiences with house renovation, I suspect that it removes a lot of waiting for people and materials to show up. If you can lay the concrete in 18 hours without any other external dependencies then it is a great savings timewise.

The total time of 2 months seems very optimistic to me.

The 18 hours doesn't include waiting for the people and materials to show up here, either. Or the time to build the printer.

> I suspect that it removes a lot of waiting for people and materials to show up.

Wouldn't you wait for the 3d printer, the operators of the 3d printer and the material to be printed out just the same?

In an organized place yes but here in Portugal the construction business is littered with one man bands that fail at every corner and have a lot of issues managing their employees and sourcing materials on time. We use bricks and concrete, not wood, and the structure and walls take a few months to complete. Hopefully, a machine that does that work in a couple of days will be less problematic. They have to fix the wall surface though, flat and smooth walls are the norm around here.

> Hopefully, a machine that does that work in a couple of days will be less problematic.

But you won’t own the machine for the same reason you don’t own a cement truck. It would be not economical to do so. And even if you would own it you have no clue how to operate it and it would not be economical for you to learn.

Just think about the consistency of the material it is extruding. If it is too runny the walls will sag. If it is too solid the material will jam the pump. Or think about the work of cleaning the pipes after work so the concrete doesn’t set in them. These are all solved problems of course, but if you are not a contractor specialising on this equipment you will just make a mess and likely ruin both the printer and the house being built.

So what will you do? You will contract the job to a specialist. Someone who knows how to operate the printer and has one to work with. What are the forces that will make that contractor any better than the ones already existing? This machine will also require employees and materials be on time. Won’t the same problems of “one man bands that fail at every corner” show up with this type of contractor too?

This basically just doing the walls in 18 hours. A framing crew could frame a conventional wall in about the same amount of time. This does nothing about the rest of finishing work.

An efficient crew of 4 people in favorable conditions (work experience, good weather, materials delivered on time) can frame a single-story, 3 bedroom house in 3 days.

I'd say the choke point are the various trades (electrical, drywall, plumbing, siding, painting, roofing, irrigation, windows, inspections, etc.) doing their thing, which can take months.

The size of that house in the pictures a good framing crew could frame that house in about 2 days. Framing is one the fastest parts in construction. Finishing is where all the other time is spent. Even a small crew would not take too long to frame a house that size.

So it really doesn't buy that much? Maybe in cost?

Concrete is pretty cheap. Lumber for framing is cheap. However, sheathing is not super cheap, but not that expensive. Siding though is not cheap even vinyl which I am not a fan of is not exactly cheap either. So not needing sheathing or siding for the exterior of the wall probably make it cheaper. So it probably would be somewhat cheaper than a conventionally framed wall. I don't know how much, but where I live 1 cubic yard of concrete is $145 dollars.

The quoted cost is half that of a traditional build, but I think it would be fairer if they compared it against a similarly finished traditional build - ie without any finish on the interior walls (plaster or similar) and so on.

I'm wondering what the thermal performance is like as well - certainly here in the UK the internal leaf of a cavity wall is usually made of aerated concrete blocks which have very good thermal performance compared to solid concrete ones.

In a cavity wall, it is the insulated cavity that provides 99% of the insulation. The inner and outer bricks, of whatever type, are so conductive that they can pretty much be ignored.

The reason aerated bricks are used is because they are lighter, and therefore cost less to produce and transport, and are therefore used wherever the structural engineer can get away with it.

That is simply untrue. I've just self built an extension and it would not pass building regs if the inner leaf was made of heavy concrete block or standard brickwork (both of which were desired for stylistic reasons).

The specific blocks used were 1.21 W/mK externally and 0.06 W/mK for the internal aircrete blocks. That's an enormous difference. UK government research indicated a 100mm cavity may be 0.6, so the inner leaf is still doing most of the work. Adding insulation to this cavity massively increases its performance, but the materials are better insulators than the air, and the concrete blocks are the worst part of the system.

[1] - https://assets.publishing.service.gov.uk/government/uploads/...

The Levittown houses (about 70m^2) could be built in a single day with a team of 36.

Do we know if these houses are built to any standards?

Does it have plumbing and wiring?

A nightmare for dust. And if you need to repair a wall good luck getting the pattern to match again. Do these people even own homes?

STL?

It would be pretty cool if you could get a 1:100 3d printed model of your house before it's actually built.

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