Comment by bane | Hacker News Reader

Comment by bane | Hacker News Reader

I think it's very interesting how prefab construction seems to pop up from time to time in the media. I grew up in a prefab house, trucked to the property in two halves and bolted together on a poured concrete foundation -- it's incredibly common.

Apartment blocks however, they seem to be locked in a perpetual demonstrator state. One, maybe two prefab buildings will go up, and then no more, eliminating the point of the effort. All kinds of stats will be provided, "built in 30 days", "providing housing for 100 families" and so on. Decades later they'll lay forgotten, or in disrepair, or make for interesting background scenery in dystopian cinema. https://en.wikipedia.org/wiki/Nakagin_Capsule_Tower

It seems that when populations have to have lots of housing, now and fast, they go more with some kind of semi-prefabbed mobile factory approaches and stamp the buildings out on site. https://www.japantimes.co.jp/wp-content/uploads/2013/09/wn20...

My guess is that it's a logistics thing. You can more efficiently move 10,000 tons of concrete and rebar to a site packed in sacks and bound in sets, on fewer trucks and in less space, than you can move the same in prefabbed boxes full of mostly empty air. Converting that raw material into the same boxes of air isn't particularly complicated or difficult and can be done at high quality on site anyways, and now you also don't have to pay to have a factory and factory workers.

I was thinking the same thing: logsitics-wise, it seems more efficient to stack all the material flat in the trailers rather than have a premade box with a lot of unused space (the room's interior).

On the other hand, having the ability to construct everything at the factory helps overcoming issues such as waste of material and lost time due to conatruction error, not to mention the health of construction workers not depending on weather conditions as much.

Its not just a logistics thing. Prefab components are mostly used for faster RoI by building quicker.

A good example of a real estate holdings company using prefab construction is mcdonalds, wawa, etc. These establishments have the same churn and burn formula. From start to finish, some of these stores can be completed in a little under a month from start of construction to open time. It makes sense for them to spend more money on prefab components. Opening sooner means faster revenue streams. Not only that, if you open in a popular area, rent/land is very high. Where I live the average rent for a store is maybe $3000 a month for a 1500 square foot area but a new chipotle in my town opened up an area with a rent of about $8000.

Your traditional real estate development takes much longer than this though. They pay for cheaper raw materials instead, as its easier to work with for each houses need. They dont have a streamlined sysyem setup for needing prefab components.

  Prefab components are mostly used for faster RoI by building quicker

... or by displacing work to places where labor and materials are cheaper (even if mainly due to poor QC and/or compromised worker safety).

A classic example of this was the imported prefab segments of the New Bay Bridge, which costs tens (hundreds?) of millions in rework costs and who-knows-how-many remaining unfixed defects.

I overstated myself here. What I meant is that for residential / small - midsized commercial buildings only, QC/defects are not as large as a concern.

Prefab components I was thinking about was prefab wall / roof / floor trusses like these http://www.buildwithbmc.com/bmc/Products/Trusses%2C-I-Joists...

Bridges are a different story all together.

Interesting points.

I doubt the logistics would make the task of prefabrication not worth doing, though.

The analogy in software that first came to mind was server vs. client-side rendering of websites. (I think much of it holds true for physical construction, too.) This topic seem to reappear every few years (2010 -> everything on the server; 2014 -> everything on the client; 2018 -> everything BACK on the server.) It will likely cycle for at least an iteration more (especially if someone finds a way to advance CPU's vertically, once again), but I believe in future, the consensus will settle to: if you can afford it -> do it on the server. (maybe it already has?)

In the web world, the "builder" would be paying a larger bill, if they would "prefabricate" what they serve to the world, but customers will be happier to get their product/service faster. On the other side - the builder will be able to get to a larger audience with smaller investment into infrastructure, if much of that computation is off-loaded to the clients.

But if we look at the overall cost of those computations - the servers should execute the same amount of computation cheaper (being a dedicated infrastructure for this specific purpose), (generally) it should be in everyone's best interest that computation happens on the server, because overall it costs less for everybody.

Which means that all that it comes down to, would be the question - how critical is this decision, in growing the service/product's customer/user-base and does the RoI make sense (i.e. would that company make more profit getting larger portion of the computation along with a larger userbase, or does it only make sense with lesser server bill)?

So while it would be cheaper, logistically, for facebook to serve their content in a completely raw format (to be fully rendered on the client), would they've still been able to grow their product to what it is right now, if they never made the switch. (I'm speculating about facebook, but I thought it was a safe bet that they do much of the rendering on the server, without confirming that first elsewhere)

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