Lower labor costs - The lighter 3' wide frame is easier to handle and plank handling costs are substantially reduce on every job. Scaffold heights - 3' wide scaffolds can be built to high elevations because of reduced plank load. Side brackets can be placed at these intervals. Every other bay must be fully crossed when scaffolding for full loads and height. Such bracing averages one horizontal to each cross, exclusive of guard rails.
Obstructions are the main problem indoors.
If the obstructions are extremely wide, putlogs may be used to bridge them like this. Sometimes, using straddle braces will solve the problem. In rare cases, tubes and clamps may be the only solution to clearing obstructions. Stationary scaffolds are the most common and usually the easiest to figure and erect. When being put up out of doors, about the only problem encountered is uneven ground conditions.