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Where are the economies of scale in homebuilding?

construction-physics.com

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Re: Where are the economies of scale in homebuilding?

#131

Post by trollbridge »

dlcarrier wrote: post #101
taneq wrote: post #15

Earlier quoted context omitted.

3D printing isn’t going to make houses hugely much cheaper. The lion’s share of the cost of a house is fit-out. Doors, windows, lighting, plumbing, cabinets, tiling, painting. What needs to happen is modular designs where the house is made out of standardised ready-made components that are mass produced in a factory and plug together to form a finished house.

I've never understood why we go through so much work, to coat the interior of our houses with easily damaged and difficult to repair materials. Who thought it was a good idea to compress dust between sheets of paper, nail it to the framing, then spray a texture onto it with more dust, and color that with a film of plastic that's cured in place, so it needs multiple coats to be thick enough to provide a consistent col…

The people who write the fire protection codes thought it was a good idea, because drywall gives you enough time to get out in a fire.

Manufactured homes (i.e. trailers) will have wallpaper integrated into the paper of the drywall so that the painting step can be skipped. Most people don't want this and would rather pay more to have a painted wall.

Re: Where are the economies of scale in homebuilding?

#132

Post by dilyevsky »

Animats wrote: post #98
pfdietz wrote: post #63

Earlier quoted context omitted.

It suggests we need to find cheaper materials from which to build homes.

Most of the world builds low-end homes from reinforced concrete. Most US buyers don't like that. (I live in a house built from cinder blocks filled with concrete and rebar, like a commercial building. It was built by a commercial builder as his own house. It looks industrial from the outside, and nice inside. I'm fine with that, but most people are not.)

Most of the world doesnt have access to good/cheap canadian lumber and we do. It would make sfhs and even small multihome projects more expensive not less if you start building them from concrete and steel. Also at the risk of stating the obvious - frame is on the order of 10-20% of the total construction cost so wouldn’t really make much of difference anyway

Re: Where are the economies of scale in homebuilding?

#133

Post by trollbridge »

hedora wrote: post #31

I think standardized codes would help a lot. Another major issue is labor mobility: Here in California, there's a big labor shortage for all blue collar trades, and even if they do live in the area, they have to spend a lot of time going to/from the job site. I think this can be largely solved by technology, but with a change of regulations, code, and division of labor in the trades. 1) Put all the power conduit, plu…

Most homes built don't use conduit for electric anymore. A few jurisdictions like Chicago require it. In any case, doing it new construction is quite easy and usually the job given to the newest apprentice electrician.

Plumbing (including HVAC lines and gas lines) already come in standard sizes and can be cut with a saw; connecting them is trivially easy. (HVAC lines might be slightly harder but everything else is easy.)

Hanging drywall and mudding it is not particularly expensive and is necessary for good fire resistance. There are cheaper techniques like pre-printing wallpaper on drywall, but most people would rather pay more to have a conventionally painted wall.

Metal roofs are already fabbed at the factory. You simply order what you want and install it. Obviously a simpler roofline is less work to install.

Solar panels can't be the roof because few want to engineer a solar panel which also is capable of being a watertight, weather-resistant roof tile that can hhandle things like snow load, driving rainstorms, and has the ability to do simple repairs. There have been attempts at this, but then it costs more than just a conventional roof plus conventional solar panels.

"3D print" a wall doesn't make sense - where is the 3D printer going to come from and where it will be set up? 3D printing stuff requires having a base, rigidity, and so on; it's just not well suited for putting up walls which is a pretty trivial task to do.

Hope this didn't sound dismissive, but the problems in homebuilding that could be solved by manufacturing techniques and automation already have been solved by the people who are in the business of making singlewides, doublewides, and modular homes; it saves a little money but doesn't save that much, and the resulting product is often quite a bit less desirable and less durable than a conventionally built house.

Re: Where are the economies of scale in homebuilding?

#134

Post by trollbridge »

fragmede wrote: post #40
peab wrote: post #35

Earlier quoted context omitted.

Exactly. The incentive isn't there.

It will, once children start being unable to afford to move out and end up having to live with their parents forever.

Not much of an incentive, is it? If people are having kids in their 40s, they probably won't even mind having an able-bodied adult around when they're in their 70s/80s.

Re: Where are the economies of scale in homebuilding?

#135

Post by trollbridge »

r-bryan wrote: post #13

Why does a carpenter cut the end off a 10-foot board to get a required 9ft-2in, thereby wasting 8% of the input and incurring dumpster charges? Suppose the architect's design specified the cutlist, to be transmitted to the board "factory", which would cut boards to the required lengths, tagging them with RFID serial numbers indexed to the design, stacking them so the first ones to be used are on the top, and truck to…

Lumber is transported from sawmills via rail cars to some depot where it will then get trucked to places like Home Depot.

There are some large-scale lumberyards that still have a railroad siding and will get lumber by the carload.

A delivery of lumber for a typical house is a full load (or more than one) via truck, and obviously a train isn't going to come to a construction jobsite. So the llumber at the construction site is already hand picked...

It's no big deal at all to cut off ends to make it fit exactly, but when framing most of the 2x4s, etc. are already the exact size you need. You just trim off the top and bottom plates at the edges of the rooms.

Re: Where are the economies of scale in homebuilding?

#136

Post by anamax »

akst wrote: post #11

A question about prefab construction came up at a talk this year in Sydney with Lucy Turnbull (Former Sydney Mayor) and Alain Bertaud (planner and author order without design), Lucy mentioned someone tried this in Sydney and went under and they never heard from them again despite promising the world. Alain mentioned that tastes (think in terms of from finishes to floor plans) change often enough where prefabricating…

One problem with prefab is that it isn't less expensive.

https://www.construction-physics.com/p/the-elusive-cost-savi...

Re: Where are the economies of scale in homebuilding?

#137

Post by AngryData »

Animats wrote: post #50

Key statement: "The fact that the ratio between costs of constructing a home and the costs of the various materials is already so low is fundamentally what makes achieving substantial economies of scale difficult." That's striking. Building houses looks labor-intensive, but, if that's correct, labor cost isn't that large a fraction of the final cost.

For a large part of residential construction if everything is new it only takes a few days to assemble for each step, the rest is just the logistics of choosing and buying the materials and getting delivery. Like even a large house can be entirely framed in a few days, a week at most, with two or three if all the materials are available and the frame design is finalized. With dimensional lumber construction there is a pretty simple way to stack and nail the floors then walls then ceilings then next floor if there is, then rafters. Work goes as fast as you can toss lumber and shoot nails. Everything so with simple blueprints of where the walls are, the height of the walls, and window and door placements. For a framer its like constructing with legos. Then a roof can be put on in half a day, siding 2-3 days, electrical and plumbing a day or two, drywall a day or two to hang and a day or two to mud and sand, painting can be done in a day or two. Getting decent trim might take longer, but it is also a more skilled and detail orientated work. With framing you can ignore 1/16th gaps and everything will settle and flex into a solid foundation. With pieces of trim a 1/16th gap could be a visible problem.

You could potentially go from nothing to an entire nearly finished house in 2 weeks worth of labor, however because the framers, electrocutions, plumbers, siding, flooring, drywall guys are often all separate contractors and the shipping for all those materials are all on different schedules it takes longer. Or if a few guys are doing it all, they will lose a bit of speed by not being specialists for each task, but can make up that time having a more centrally coordinated plan of attack.

Even then the permits and design planning and choosing the windows and siding and flooring and all that is often still the biggest speed bottleneck.

Re: Where are the economies of scale in homebuilding?

#138

Post by AngryData »

There isn't a lot of room for scaled improvements because labor speed is almost never the bottleneck in residential construction. It is the logistics of all the supplies, of all the subcontractors, the permitting, which all take considerable time and wait. And if people are building their own custom home, getting them to actually choose what windows, floors, doors, siding, roofing materials, or even just finalize the layout for framing can take a lot of time. The windows could all be installed in a few hours, but getting somebody to choose what windows they want could take days or longer, days for delivery, days for the contractors schedule to align while they are juggling a bunch of different jobs because rarely do they get to just sit on one jobsite for multiple days having everything they need ready to go.

I think people overestimate the labor requirement/cost for building new construction because so much of their experience is dealing with repairs and maintenance and adapting old construction. While it might take a day or two to fix one already existent bathroom because of tearing old stuff out, not making a massive mess, fishing tools and materials through little access holes, you can plumb an entire new framed house with multiple bathrooms that doesn't have drywall in the way or people living in it in the same time or less. In the time it takes to fix your old existent leaking tub, in new construction a plumber could install 3 tubs, 5 toilets, 7 sinks, and hot water heater with all new pipe. And it will be a much easier task with far less struggle and both physical and mental anguish. Construction guys absolutely love new construction because it is literally 10x easier and without having to hack together old standards into new standards.

Material costs are at minimum atleast 50% of the cost of new construction, some contractors will just automatically bid everything at double the base material cost and make decent money off that. And potentially even higher total cost will be just material if everything is decided beforehand and all the materials are ready to go on site, because half of your labor cost is paying for all these contractors and subcontractors to travel around to different sites at different times. If they can put in a solid 20-30 hours on a single project without leaving the job site, they are going to be happy and be making bank and able to put in low bids. If they gotta return to a single job site 20 separate times from repeatably going to stores, waiting for supply deliveries, waiting for decisions, they are going to want some compensation for it and it gets rolled into the labor cost.

Re: Where are the economies of scale in homebuilding?

#139

Post by pfdietz »

dilyevsky wrote: post #132
Animats wrote: post #98

Earlier quoted context omitted.

Most of the world builds low-end homes from reinforced concrete. Most US buyers don't like that. (I live in a house built from cinder blocks filled with concrete and rebar, like a commercial building. It was built by a commercial builder as his own house. It looks industrial from the outside, and nice inside. I'm fine with that, but most people are not.)

Most of the world doesnt have access to good/cheap canadian lumber and we do. It would make sfhs and even small multihome projects more expensive not less if you start building them from concrete and steel. Also at the risk of stating the obvious - frame is on the order of 10-20% of the total construction cost so wouldn’t really make much of difference anyway

I was noticing on my last trip to Europe that telephone/power poles were made of concrete, not wood. This was near Budapest.

Re: Where are the economies of scale in homebuilding?

#140

Post by [deleted] »

josh_s wrote: post #54

Lots of interest comments on the efficiency of building homes. The bigger issue is the cost of land. The differential for land to build is often 10:1. So even if the prefab shave 10-20% the price for a custom build, it's still not making much of a difference for the normal buyer. unless a develop or government was opening up mutiple parcels of land well below the costs to build a house, prefab is not really going to…

[deleted]
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