Comment by iandanforth | Hacker News Reader

Comment by iandanforth | Hacker News Reader

I was onsite at a modular manufacturer today and I can tell you a lot of what is said here is just wrong. The cost estimate is not quality adjusted. If you look at cost per square foot and don't take into account the quality of work provided then you haven't calculated anything worth knowing. Also the article doesn't price out the value of speed. Modular can take half the time to move-in as stick build.

I agree there are plenty of points for improving efficiency. For example the builder I visited was not vertically integrated at all. They bought manufacturing time on a modular line for their box plans, worked with external designers and all kinds of subs they can't guarantee for onsite work. But having seen it up close I can tell you there is far more opportunity for process improvement on a assembly line (even if each build is custom) than there is in the field.

If you look to Japan, Toyota is getting into modular with steel framing that is way ahead of anything in the states. I look forward to that being available here.

Modular home manufacturing has been around for many decades. It certainly has a role to play, but if it were that much better it would have put the traditional contractors out of work long ago.

The main problem is transportation. You can make every box the size of a standard shipping container, and thus greatly reduce your home design options and size of rooms while still spending plenty on shipping. Or you can make bigger boxes, which gives you more design flexibility but still a lot less than stick building does. And with the bigger boxes you need special highway permits, escort vehicles, etc.

And then, when you have everything on site, there's still a lot to be done. Tree clearing, grading, excavation, concrete work, paving, utility lines, on-site assembly of the boxes (using an expensive crane)...

When you've added it all up, modular isn't the obvious improvement that it seems to be at first glance.

Site preparation is a fixed cost, certainly?

I suspect that transportation is not the issue, because any way you slice it, building materials come with large footprints. The footprint can be in the factory or on site, but you need big trucks moving stuff around in all cases, and every day the site has a crew on it is a day that generates vehicular traffic. Since the total time for the build goes down in modular, it can be surmised that less public space-over-time is used, even if more bandwidth is used at certain points.

As grandparent says, modular's biggest selling point is in quality control, which improves project risk profile. Factory assembly lends itself to systematic controls; one of the most common headlines in construction failures is "contractor used wrong parts or materials". That can quickly spiral into massive cost overruns when we're talking about something they assembled on site and realized they screwed up only after it's buried in the ground. If the whole subassembly arrives on site pre-checked, there's less that can go wrong. And "subassembly" is the way to think about it, not "box". It's certainly possible to devise a clever modular structure that ships packed but encapsulates more of the desired features with less sawing, nailing and bolting. Boxy shape language is not unique to modular, it appears all throughout industrial goods.

I have had some professional experience with pre-fabricated houses (typically multi-flat buildings) in the '90's, and of course it may well depend on the country, on local codes and availability and cost of site workers, but the overall lesson we learned at the time after n designing and manufacturing tests was that the only real difference was construction times (at the same level of quality), an old related post of mine:

https://news.ycombinator.com/item?id=24764117

I grew up in a "manufactured home" and have been shocked by the ambient draftiness in every site-built house I've inhabited since. Similarly rated materials end up with nowhere near as tightly sealed an end result. Now I'm in an extremely high-efficiency condo, and while there are certainly no drafts, air sensors confirm the windows don't open enough to get decent ventilation. Makes me miss the huge banks of properly openable windows on the manufactured home...

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