What happens if the input is incomplete

The three possible routes

1. We ask back

The base case. We ask, and we wait for the answer.

2. We work to a recorded assumption

If the answer does not arrive in time but the work cannot stop, we continue to a written, recorded assumption and mark on the drawings what it was.

That works — but only as long as the assumption stays visible. If somebody later removes the note from the drawing, the assumption becomes invisible, and that is where the trouble starts.

3. The work stops

If the gap cannot be bridged even by assumption — no ground investigation for a foundation, say — we say that it has stopped.

What we do not do

Assume silently. Design rests on assumptions: actions, restraint conditions, build-up weights. If an assumption is not stated, nobody can check it — and the fault surfaces during construction, when it is expensive. What structural software is for.

The commonest gaps

The weight of the build-up

“We’ll decide later.” Meanwhile the size of the floor joist depends on it.

The weight and position of plant

A plant unit on a roof is a concentrated load. If it emerges later, a transfer member is needed.

The opening layout

If an opening changes during detailed design, it affects everything from the lintel to the anchorage. Openings and lintels.

The sensitivity of the finish

A rigid finish calls for a stricter deflection limit. If that emerges later the structure does not comply — even though the strength is fine. Deflection limits.

What we ask of you

If you do not know something, say that you do not know. That is far better than an uncertain figure we take to be certain.

The point

A missing figure is manageable. An unstated assumption is not. So we write them all down, and we do not remove them from the drawings.