A 1:20 hand section takes about forty minutes. In that time you will discover the things a model would have quietly resolved for you: the cill that cannot drain, the insulation line that breaks at the parapet, the door that opens into a downpipe.

What the pencil catches

Drawing forces sequence. You cannot draw a junction without deciding what is installed first, and that decision is where most buildability problems live. Software will happily let two components occupy the same 30 mm.

Where the model wins

We are not romantics about this. Coordination across disciplines, clash detection, quantity take-off, the model does all of it better. The point is the order: draw to think, model to build.

Every project in this office starts with a hand section at 1:20 before anyone opens a modelling package. It has never once slowed us down.