5 ms·

An overview of concrete forming technology

89 points by jseliger 4y ago

monkmartinez 4y ago
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 https://www.nist.gov/fire
- evilos 4y ago
  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?
  - psd1 4y ago
    Thermal mass is great to smooth diurnal variance
    - mikeyouse 4y ago
      Thermal mass inside the conditioned envelope is.. less so on the exterior of the house. Especially if it thermally bridges from outside to inside.
    - bluGill 4y ago
      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.
  - l1tany11 4y ago
    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+.
- majormajor 4y ago
  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?
  - dylan604 4y ago
    How to spot an HNer in a home construction conversation: Add new fiber runs.
  - bluGill 4y ago
    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.
  - dsfyu404ed 4y ago
    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.
- dylan604 4y ago
  > 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.
- shrubble 4y ago
  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'.
prpl 4y ago
I literally was reading this substack last week and almost posted. There’s some other good articles in there.
- paulhart 4y ago
  It’s very popular here: https://news.ycombinator.com/from?site=constructionphysics.substack.com https://news.ycombinator.com/from?site=constructionphysics.s...
eo3x0 4y ago
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.
- majormajor 4y ago
  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."
- worik 4y ago
  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.
snake_plissken 4y ago
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 https://www.youtube.com/watch?v=sforIL7rU3Q.
- jaclaz 4y ago
  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 https://www.youtube.com/watch?v=rIMxXsyzzM8
deleted 4y ago
[deleted]
kragen 4y ago
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
joeman1000 4y ago
This is a better overview than any I saw in my undergrad studies in Civil Eng.
ThouYS 4y ago
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.
DrNosferatu 4y ago
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!
DrNosferatu 4y ago
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!

89 points by jseliger 4y ago

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 https://www.nist.gov/fire

evilos 4y ago
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?
- psd1 4y ago
  Thermal mass is great to smooth diurnal variance
  - mikeyouse 4y ago
    Thermal mass inside the conditioned envelope is.. less so on the exterior of the house. Especially if it thermally bridges from outside to inside.
  - bluGill 4y ago
    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.
- l1tany11 4y ago
  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+.
majormajor 4y ago
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?
- dylan604 4y ago
  How to spot an HNer in a home construction conversation: Add new fiber runs.
- bluGill 4y ago
  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.
- dsfyu404ed 4y ago
  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.
dylan604 4y ago
> 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.
shrubble 4y ago
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'.

prpl 4y ago

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

paulhart 4y ago
It’s very popular here: https://news.ycombinator.com/from?site=constructionphysics.substack.com https://news.ycombinator.com/from?site=constructionphysics.s...

eo3x0 4y ago

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.

majormajor 4y ago
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."
worik 4y ago
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.

snake_plissken 4y ago

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 https://www.youtube.com/watch?v=sforIL7rU3Q.

jaclaz 4y ago
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 https://www.youtube.com/watch?v=rIMxXsyzzM8

deleted 4y ago

[deleted]

kragen 4y ago

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

joeman1000 4y ago

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

ThouYS 4y ago

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.

DrNosferatu 4y ago

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!

DrNosferatu 4y ago

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!