If you're building something as big as a house, as part of the "profit and Scarcity" thread has been going, you're probably *not* going to be assembling it atom by atom.
Drexler's covered several varieties of manufacturing:
Atom-by-atom: this takes place in a tank or "pond" where the assemblers organizae themselves into the shape of the final product, then grab feedstock out of the fluid to assemble the structures. This method let's you build, massively parallel, on a 3-d basis; building a house in the open would probably be as a series of 2-d layers (which would probably be hopelessly slow), or would use some sort of scaffolding (set up prefab wall-molds into which you pump the fluid?).
Module-by-module: this uses a pond, too, except the assemblers use prefab micromodules -- motors, struts, lights, etc -- that have been constructed elsewhere. These active modules would form an active structure on the microscopic scale; alternatively you could build a "dumb" object out of "dumb" modules: cubic-micron pieces of metal, etc. This prefab approach speeds assembly by about a factor of a thousand; in _Engines_ Drexler has a rocket engine grown atom-by-atom in about a day; in _Unbounding_ an emergency tent is slapped together in less than a minute.
Assembly line: rather than using general-purpose, mobile assemblers with robot arms, this approach uses specialized devices -- analogous to conveyor belts and hydraulic presses -- to move feedstock atoms/molecules around and break them apart/squish them together into a specific product.
So, if you're building a house, it's probably more efficient to have it constructed as a number of prefab (but by no means _standardized_) modules, which could be plugged together (by all those micron-sized mechanical devices) into a single unit. (I suppose you could actually have assemblers join then on the molecular level, if you wanted)
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= PHILLIP THORNE, <thornp2@rpi.edu> URL: http://www.rpi.edu/~thornp2 =
= RENSSELAER POLYTECHNIC INSTITUTE (Always under construction!) =
= TROY, NEW YORK, USA "It's the boundary conditions that get you." =
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