An overview of concrete forming technology | Hacker News Reader

An overview of concrete forming technology

constructionphysics.substack.com

89 pointsjseliger34 comments

I’ve recently started research construction costs due to a desire to build a custom house. Not sure what it’s like in other areas of the country, but in California, everything is negligible compared to labor costs. You would figure that means we get to use all sorts of cool materials and techniques here because the costs of materials are marginal, but no, in fact it’s the other way around. Unless you’re willing to put up with the cheapest and lowest common denominator combination of materials and techniques, people look at you funny and assume you’re okay with your costs blowing up by 10x because now the labor involved is not standard. With the million dollar (and easily higher) house construction costs, instead of the best, we get the absolute worst. That includes using the bare minimum amount of concrete in our shallow foundations that would be a laughing stock anywhere else in the world.

It would be like if every programmer only does 90s style PHP because software developers are expensive enough already and you asking for the latest Python or JavaScript is a desire to pay space rocket numbers.

I'm a custom builder in SoCal and I can say a lot about what you are talking about. There are a few main issues with construction of a house that pop up all the time:

1) Most people just want the cheapest possible. So most contractors are used to dealing with that. Even if it's not really the cheapest long term, and makes no sense.

2) Perspective and incentive. Does your framer know, or care how much money/time engineered lumber can save when it comes time to drywall/tile/etc? Not really, because his material cost in the bid will go up, and he doesn't want to be noncompetitive.

3) Most people think the code is very rigid. There is a section of code that is prescriptive, but there's also a section that is engineered/calculated which is what makes the code very flexible. You can do pretty much whatever you want if you can show it will perform.

4) Guys are afraid of callbacks/lawsuits. So they tend to want to do the same thing, the same way. Keep doing what has been working. There is a lot of resistance to trying new materials, methods, etc. Even if they aren't new, they may be new to that contractor. And they are (rightfully) wary of the training time, and increased likelihood of making a mistake doing something for the first time. So they will send bids with the "fuck you" price.

5) If you want to use some material/method that is not super common, sometimes you are best off asking for references at the suppliers. That way you can try and get a competitive bid instead of asking a guy to do something he doesn't want to do.

6) IDK what you are talking about regarding the foundation. Usually a contractor is just going to follow the plan, and do what the structural engineer says to do, as the structural engineer has to sign off and do inspections. So it makes bidding and executing quite simple. I've spoken to engineers about different foundation strategies. If you want a big, thick, mat foundation I don't see why the engineer wouldn't be open to that. They are very simple...no contractor will care or bat an eye.

> there's also a section that is engineered/calculated which is what makes the code very flexible

That section of the code requires a PE stamp.

PEs don't work on residential houses unless it's a mansion or a cookie-cutter subdivision.

In certain markets/jurisdictions it's standard/common to have multiple PEs stamp multiple different parts of the plans. For single family homes. Probably the lowest hanging fruit is energy calcs. For instance getting a PE to do title 24 calcs and stamp a plan is a couple hundred bucks. For $200 you open up a LOT of flexibility in design, materials, etc. Everything from window/door sizes, styles and locations to HVAC duct type.

What’s a PE?

Professional Engineer: https://www.nspe.org/resources/licensure/what-pe

Are you open to new clients? I'm nearing the stage of building a custom home in LA and would love to work with a builder that frequents these boards.

Yes.

I have been doing quite a bit of building over the last decade at my house and will do more in the coming decade.

Definitely using as many prefabricated materials from Western Europe as I can.

There have been so many advances in manufacturing in the last two decades and so little sign of them on building sites.

I wish I could use locally manufacturers but where I live (Aotearoa) the building industry has become obsessed with using the lowest quality wood available, (tannalised pinus radiata) and plastic whatsits up the whazo and then supplying the parts unfinished. Meaning weeks of painting and finishing.

In Western Europe they have much better timber and an appreciation of quality we do not have.

Building sites should be places where things are assembled, not constructed. The construction should happen in a factory mostly automated with modern machinery.

Dumping the carbon to ship a panelized structure from western Europe is a huge use of resources, even if you aren't forced to actually shoulder the burden of externalities like carbon emission and irresponsible old growth harvest.

Building with pine actually works really, really well - pine is both cheap and plentiful, and depending on exact geography it's generally a reasonably small carbon footprint. We've spent a long time figuring out how to build well with less than ideal materials and the techniques to do so are well understood, if not always implemented properly. The difference between a well constructed pine framed structure and a poorly constructed one is in the details. Find someone who is paying the proper attention to those details and you'll have a superior product without the massive supply chain and all that entails.

That doesn’t change OPs point though. Pine is not a good wood and it requires a ton of work to finish it (plaster board, stopping and paint). It’s only attribute is that it grows fast.

Another issue is that building sites have massive wastage. It’s just so demoralising walking past their skips. If walls were prefabricated and shipped it would be hard to do worse than NZs current standard, even with shipping from a long distance.

I’ve seen over ordered materials just binned rather than collected and returned or sold.

> Dumping the carbon to ship a panelized structure from western Europe is a huge use of resources,

Containerised hipping is very efficient. My point is it is better to use those resources rather than the local building industry. Very odd.

I don't think your attempt to show a difference between that and software makes your point.

The bulk of software project costs is labor. And there are certainly a lot of business folks who say "ok, the bulk of the cost is labor, so labor is a commodity, so I should be able to hire any programmer to do any type of software" and hire cheap devs and see things go sideways if they don't stick to fairly simple, rote, lowest-common-denominator technologies that are much closer to 90s-style-PHP than they are to "the latest Python or Javascript."

If you've spent your whole career in coastal California startups or FANG you may never have seen these people at all, they don't really live in the same job posting/hiring/skill set universe. But it strikes me as very similar to "labor is the most expensive part, concrete vs lumber isn't gonna be that different in parts, so I should be able to pay the same for labor for the unusual things."

> I’ve recently started research construction costs due to a desire to build a custom house.

Worth examining pre-fabricated homes, where most of the work is done at a factory and the semi-finished wall panels are delivered by trucks, craned into position, and tied together like Lego® blocks:

* https://www.youtube.com/watch?v=r-RTlbv84T8

* https://www.youtube.com/watch?v=aeHkVeJO6PE

* https://www.youtube.com/watch?v=QX3QZVG-18E

* https://www.youtube.com/watch?v=FoBtE7Dd4aU

Being a firefighter, I am tangentially intimate[1] with construction methods for dwellings, be they commercial or private. I am fascinated with concrete and the myriad of ways it is formed. My nerdy side really wants to build a concrete 3D printer and print a compound for my family. My profession reminds me that building codes and laws are mostly written in blood and are codes/laws for a reason.

How could we speed up the process of adopting codes across the US? 1 hour to my south in Mexico, one can basically build anything they want in concrete and there really isn't a regulatory body that would stop them. The probabilities of earthquakes and hurricanes in that area are quite low, no really reason to build for snow loads, but definitely for wind. Yet, on the other side of that imaginary line, in the same desert with the same probabilities; Contractors must build houses that can withstand loads and forces that will likely not happen if the house was around for 200 years.

Todays homes are not generally built with concrete except for the slab on grade. They burn hotter and faster than anytime in the history of shelter.[2] This is mostly due to the contents we place inside, but a large part is the gluing of structural elements out of fractional lumber. We seal and insulate these newer houses up tight, because they have very little thermal mass, with petroleum based products that contribute to fire load as well.

Concrete would be a better choice for homes in the US, but its cost prohibitive due to labor and materials. I don't know for sure, but the price for building with concrete seems like it is mostly artificial. That is, using 8 x 8 blocks for walls seems excessive when compared to the layered 2 x 4 -> 1/2" OSB sheathing (only on corners) -> Foam/chickenwire -> Stucco sandwich. Why don't we see tilt-up concrete homes? Or columnar concrete homes? It all just moves so slowly...

[1] New phrase? I am not an architect or contractor, but I know my way around most building systems past and present to include mechanical, electrical and structural.

[2] https://www.nist.gov/fire

> Why don't we see tilt-up concrete homes?

When I was a kid, my dad was in commercial construction. During the 80s I was old enough to remember things my dad talked about work, but not really able to fully understand them. I have distinct memories of my dad always dissing prefab concrete constructions that became popular, but I don't remember why they made fun of them. My dad also taught building trades at a local high school for a time, and he had stories about how the houses the students built were of such better construction than modern houses because they were learning the proper ways of construction vs learning how to cut corners and speed up the process while saving money. There were definite comments about how home builders were interested in using prefab walls so that they were always the same vs variance between crews. He was not a fan.

The beauty of stick-build houses is that they are easily modifiable. Move a wall. Build an extension. Move the plumbing. Add new fiber runs. All very incremental, marginal-cost work.

I'm very curious about your statement about insulation leading to faster fires, though. Like you say, codes tend to move very conservatively - are these new insulative house wrap products and such not getting fire tested as part of their approval?

Stick built is also more flexibility in terms of timetable. The roofers, can be on site before the framers are done. The electricians and plumbers show up right as the framers wrap up their work and before the roofers are done. Or they can wait a week because as long as they gets done before drywall nobody cares. Insulation can happen concurrent with plumbing and electrical or after. When you consider that all these parties have N jobs that need doing this added flexibility to show up early or late in the process helps a lot. Concrete is somewhat flexible but isn't that flexible in terms of timetable of all the steps.

There are competing concerns ever since the 1970s energy crisis insulation has been required. The people doing that often didn't talk to the health and safety guys. Some insulation doesn't burn, but some burns fast. Some safe while others are toxic. We discover issues and adjust code to fix it. Them Someone discovers something new and it looks great until years later we discover something we didn't know and codes have to adjust to something we didn't know.

How to spot an HNer in a home construction conversation:

Add new fiber runs.

Some have worked around the barriers for non traditional building by getting an approved frame, then ensuring that the approval process is ok with any form of 'infill'. For concrete, the frame of wood or steel could be approved, then you pour/print the rest which is not officially 'structural'.

I don't think we should be moving in the direction of insulating our dwellings less at this point since we are actively trying to reduce energy/emissions and heating/cooling is a big factor in that.

But maybe concrete structures are more insulating than I realize?

It has an R value of less than .5 per inch. Which is pretty much terrible to the point that it's negligible. A typical wall may have an r-value of 20, and a roof is 30+.

Thermal mass is great to smooth diurnal variance

Thermal mass inside the conditioned envelope is.. less so on the exterior of the house. Especially if it thermally bridges from outside to inside.

Thermal mass is great for hot days and cold nights in areas near the equator. Most people live where sometimes they day doesn't get hot enough at least once in the year. Even when day of not enough balance and you either deal with the cold (frozen pipe is the big issues, humans can wear more clothes), and insulation is the only answer. Well you can just turn on the heat, heat but without insulation you need a lot. (Such areas tend to not have modern furnaces, burning tires is common for heat despite the toxic fumes)

In short, thermal mass is overrated.

I was curious about how the self-climbing forms work. Here is a video showing how one such system pushes/pulls itself (~45 seconds in): https://www.youtube.com/watch?v=sforIL7rU3Q.

JFYI, there are two kinds of climbing formworks, the one you posted the video and the other one that makes use of pistons to slide (used mostly for tall pillars in bridges), like these:

https://www.youtube.com/watch?v=rIMxXsyzzM8

We hear a lot of breakthrough-sounding news about novel methods of constructing concrete buildings - 3D printed, inflatable-formed, etc. - claiming to "solve housing" and "be able to give all of Humanity a house".

But I don't understand what problem exactly are these technologies trying to solve:

- Is there anyone in the World without (quality) housing, that can afford the concrete itself but not the labor and the cost of traditional methods to construct with it?

Curious to hear your views / insight from this field. Thanks!

A bit off-topic, but:

- Why is housing construction in the US so fragile?

We see all the time news footage of hurricanes making short work of US homes that are made of wood - and yet - after, they are reconstructed new again out of wood!

- Don't different types of construction have different insurance premiums? - Why isn't housing in the US built out of reinforced concrete & bricks, like in Europe?

Curious to hear your views / insight from this field. Thanks!

Isn't it ironic that we can give concrete "virtually any form", and yet most new buildings are boring cubes? Old brick houses used to have a lot more ornamentation.

And if you think about it, it makes sense. To ornament, simply use a differently colored brick, or turn it 45 degrees. Or give the wall a slight convex shape. You were just a lot more flexible.

this is pretty interesting, but i wonder why he omitted ferrocement

or paolo soleri's approach of building your form (for a building without vertical walls!) by piling up sand

I literally was reading this substack last week and almost posted. There’s some other good articles in there.

This is a better overview than any I saw in my undergrad studies in Civil Eng.

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