How a Building Gets Made Off-Site

The factory floor is the opposite of a building site in almost every way that matters for making things well. It is enclosed and climate-buffered, so monsoon, dust and heat do not stop work or spoil a finish; adhesives cure at a known temperature, timber stays dry, and paint goes on in clean air. It is lit evenly from above, so people see what they are doing without squinting into sun or shadow. It is level and hard, so trolleys roll, tables sit true, and measurements taken off the floor mean something. And it is permanent: the same power, extraction, compressed air, cranes and racking are there every day, instead of being dragged around a changing site.

The floor is usually arranged as a line (or a set of lines and cells), because the work is going to move through a fixed sequence of operations. Think of it as a street with workshops down each side. At one end raw material arrives - studs, sheet goods, insulation, windows, fittings. At the other end a finished panel or module rolls off. In between sit stations, each set up to do one slice of the work repeatedly: a framing station, a sheathing station, a services station, an insulation and lining station, a finishing station. The layout is deliberate, not accidental: stations are placed in the order the work needs them, with the material each one consumes stored right beside it, so nobody walks far and nothing travels more than it must.

Compare that with a site, where the 'workstation' is wherever the work happens to be - up a ladder, in a trench, on a slab open to the sky - and where each trade waits for the one before to clear the space. On a site, position is fixed and people move to it; on a factory line, the position moves and the people stay. That single difference is what lets a factory hold quality, run in any weather, keep tools and jigs permanently set up, and let less-experienced workers produce reliable results by repeating a bounded task. It is also why the factory is unforgiving of surprises: a line is tuned to make a known thing, and an unexpected, one-off variation jams it in a way a flexible site crew would simply absorb.

The humble hero of the factory floor is the jig - a purpose-built frame, table or fixture that holds the parts in exactly the right place while they are joined. A framing jig is a steel table with fixed stops and clamps: the studs and rails drop against the stops, so the frame that gets nailed or screwed together is square and the right size *without anyone measuring it again*. A welding jig holds steel members at the correct angle. A drilling fixture puts every hole in the same place. Alongside jigs sit fixtures and go/no-go gauges - simple tools that either accept a part or reject it, so correctness is checked by feel, not by reading a tape.

The principle behind all of them is profound and worth stating plainly: a jig builds accuracy into the process rather than relying on the skill and care of each individual worker each time. On a site, a square corner depends on someone measuring diagonals carefully, every corner, all day, while tired and rushed. In a factory, the jig makes the square corner a by-product of simply loading the parts and pressing go. This is how repetition turns into quality: the first unit's accuracy is engineered once, into the setup, and then every unit inherits it. It is also how a factory can use less-experienced labour to produce consistent work - the judgement is captured in the fixture, not demanded of the hand.

This connects straight back to the design discipline of the earlier modules. Jigs only pay off if the thing being made is standard and repeated - a jig for a one-off shape is just an expensive table. So the factory rewards designs with a disciplined grid, a limited kit of parts and consistent connections (Module 5), because those are what let a jig be built once and used thousands of times. It is the physical reason DfMA insists on standardisation: the jig, not the drawing, is where standardisation actually cashes out on the floor. And there is a sharp edge, picked up in lesson 6.3: because a jig stamps its geometry onto every unit, a jig that is set up wrong stamps the *same error* onto every unit - so how jigs are set and checked is a quality question, not just a productivity one.

Let us follow a single piece - say a wall panel, though a volumetric module runs the same way at larger scale - down the line, station by station, to make the flow concrete.

Station 1, framing. On the squaring jig, studs and rails are laid against the stops and fixed into a flat, square frame. The panel is now a skeleton with known dimensions. Station 2, sheathing and squaring check. A board is fixed to one face, which both stiffens the panel and locks its geometry; a quick diagonal or gauge check confirms it is still square before it moves on. Station 3, first-fix services. With the panel still open on one side and at bench height, electrical conduit, boxes and any pipework are run into the frame - far easier reaching into an open wall on a table than fishing cables through a built wall on site. Station 4, insulation and lining. Insulation is set into the cavity and the second face is lined, closing the panel. Station 5, finishing. Windows or doors are fitted into pre-formed openings, external cladding or internal finishes are applied, and the panel is cleaned, labelled and checked.

Two things about this sequence matter more than the specific stations (which vary by product and manufacturer). First, at each station the piece is presented to the worker in the best possible position - flat, open, at waist height, both hands free, the right tools and parts within reach. Work that would be awkward and error-prone on a finished building in place - running a cable, setting a window square, taping a joint overhead - becomes easy bench work. Second, the piece only moves on when its station's job is done and checked, so each stage hands a known-good piece to the next. A volumetric module simply does this in three dimensions and at room scale: floor cassette, then walls stood and fixed to it, then ceiling, then services, linings, finishes, fittings and even furniture, until a complete room rolls off - sometimes with the kettle in the cupboard. The logic is identical; only the size of the thing moving down the line changes.

Pull the threads together and the factory's advantages are really one advantage seen from several sides. Because the work comes to the worker in a controlled place, posture is good and fatigue and error fall; because the environment is stable, weather never stops work and finishes cure properly; because jigs and fixtures are permanently set up, accuracy is repeatable and labour can be less specialised; because the line is sequenced and material is positioned, people and parts barely travel and nothing waits in the mud; and - the big programme lever from Module 0 - because the factory runs while site groundwork proceeds in parallel, two things happen at once that a site would do one after the other. Add inspection at the bench (lesson 6.3) and you see why factory-made work tends to be more consistent than open-site work.

But the factory extracts a price, and naming it honestly is the point of this course. A line is tuned to make a known thing many times. It cannot improvise, negotiate or fix-in-place the way a skilled site crew absorbs surprises. A bespoke one-off jams the line; a late change means re-tooling, re-sequencing, and scrap. Everything the factory is good at depends on the design being settled, standardised and detailed for the line before production starts. The shop floor is where DfMA either pays off or bites: a design that respects the grid, repeats its parts, and details connections for assembly flows down the line; a design that ignored all that arrives at the factory door as a problem.

So the walk down the line is not just a tour - it is the clearest possible argument for designing the way the earlier modules insisted. When you draw a panel or a module from now on, picture it on the jig and moving down the stations: is every operation easy to do at a bench, is the piece standard enough to justify a jig, does it only fit one way, can each stage be checked before hand-off? Those are factory questions, and answering them at the drawing board is what 'designing for manufacture' actually means. The binding specifics - line design, cycle times, the real process for a given product - belong to the chosen manufacturer and their tested system; your job is to design so their factory can do what it does best.