Building (houses) is not an industry, it is essentially artisan work, some (few) of the inefficiencies could (and are) already reduced in large size projects, b

Building (houses) is not an industry, it is essentially artisan work, some (few) of the inefficiencies could (and are) already reduced in large size projects, but such projects are rare, normally each house is different from the one built before and from the one that will be built later. Even on relatively large projects (let's say 4 buildings with 50 apartments) you will have scale savings on costs but not great overall savings in time (time passing), that is a constant, parallelizing of course helps, so if you can build just one of them in 18-24 months, you can as well build four of them in the same 18-24 months employing a little less than 4 time the hours and equipment, so at the end you can say that it took 6 months to build one of the blocks on average, but it actually took 24 months from the beginning to the end.