[HN Gopher] An overview of concrete forming technology
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An overview of concrete forming technology
Author : jseliger
Score : 28 points
Date : 2022-11-11 16:17 UTC (6 hours ago)
(HTM) web link (constructionphysics.substack.com)
(TXT) w3m dump (constructionphysics.substack.com)
| monkmartinez wrote:
| 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
| majormajor wrote:
| 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 wrote:
| How to spot an HNer in a home construction conversation:
|
| Add new fiber runs.
| dylan604 wrote:
| > 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 wrote:
| 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'.
| evilos wrote:
| 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 wrote:
| Thermal mass is great to smooth diurnal variance
| snake_plissken wrote:
| 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.
| hirundo wrote:
| I'm new to the 3D printing hobby with my first machine just a few
| weeks old, having loads of fun printing all the things, finding
| out what it can do.
|
| The workflow is basically, copy/design the part in a CAD, export
| it to an STL file. Open that in a "slicer" to generate the
| commands for the printer. Send those to the printer and it
| starts. Try something simple and it just works. Get ambitious and
| be prepared for starting over a lot.
|
| I love the idea of doing the same thing for a house, except the
| gcode gets delivered to a very large concrete printer on site.
| Better get an expert to check it carefully first, because a bad
| print is a financial disaster. Print lots of scaled down
| prototypes in plastic.
|
| But the amount of flexibility inherent is astounding, daunting
| even. If we still have rows of cookie cutter homes built by fused
| deposition modeling, it will because of regulations rather than
| cost constraints. It has the potential to generate a cambrian
| explosion in architecture.
| prpl wrote:
| I literally was reading this substack last week and almost
| posted. There's some other good articles in there.
| eo3x0 wrote:
| 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 wrote:
| 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 wrote:
| 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.
| idiotsecant wrote:
| 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.
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