What gets produced
Fabrication drawings. One per member type: overall length, every hole position, every cut and cope, weld details and sizes, and the mark that identifies it.
Assembly drawings. How sub-assemblies go together in the workshop before they leave.
Erection drawings. Where each marked member goes on site, and in what order.
Bills of material. Cut lists, plate lists and bolt schedules — the procurement basis for the whole package.
Why it is the cheapest place to get things right
The cost of an error scales with how late it is found:
- At detailing, a wrong connection is a drawing revision
- At fabrication, it is a member remade and material wasted
- At erection, it is a crane standing idle, a trade waiting, and a programme slipping
That is the whole argument for spending real time here rather than rushing to cutting. A workshop that starts cutting before detailing is complete is a workshop that will be remaking members.
Tolerances: accurate steel meeting an inaccurate building
Steel is fabricated to fine tolerances. Concrete, masonry and existing buildings are not.
So a large part of detailing is deciding where adjustment lives:
- slotted holes in the right direction and the right amount
- packing plates at base connections and at interfaces with concrete
- adjustable bases where the level of a slab cannot be relied on
- site-drilled holes deliberately left where a dimension cannot be established in advance
Get this wrong in the tight direction and nothing fits. Get it wrong in the loose direction and the connection slips or looks poor. See bolted fabrication for how those tolerances are actually used.
Sequence
Erection order is a detailing decision, not a site one. Each stage has to be stable enough to support the next, temporary bracing has to be planned, and the sequence has to match the crane’s reach and the site access.
On a constrained Mumbai site, this frequently drives the structural arrangement rather than following it.
Marking and traceability
Every piece carries a mark corresponding to the drawings, so the right member reaches the right position. On a structure of any size this is what prevents the slow, expensive confusion of similar-looking members being installed in the wrong place.
Design versus detailing
Worth being explicit. Detailing takes an engineer’s design and makes it buildable. It does not replace the design.
Where a project arrives without structural design behind it, we say so. Fabricating an undesigned structure is not something we will quietly do — see structural fabrication for how a job normally runs from drawings to erection.