Frame scaffolding is the usual choice for painting, siding, masonry or window work on a house. It is built from bays (the length between two frames) stacked in levels (the height of one frame). Knowing the number of bays and levels gives the frames, planks and rental cost.
How the calculation works
- Bays = wall length ÷ bay length, rounded up
- Levels = height of the working platform ÷ frame height, rounded up
- End frames = (bays + 1) × levels
- Planks = bays × levels × planks per bay, if every level is decked
- Rental = bays × levels × weekly rate × weeks
Standard frames in the United States are 5 ft wide and 5 ft or 6 ft 4 in tall (walk-through frames are about 6.5 ft), joined by cross braces that set bays of 7 ft (also 5, 8 or 10 ft).
Example
To work on a 40 ft wall from a platform at 18 ft, you need 6 bays of 7 ft and 3 levels of 6.5 ft frames. That is 21 end frames and 36 planks if every level is decked with two planks per bay. The top platform ends up at 19.5 ft. At $10 per bay and level per week, two weeks of rental cost about $360.
What else to order
- Cross braces: two per bay per level (one on each side).
- Base plates or screw jacks: one per leg, plus mudsills on soft ground.
- Guardrails, midrails and toeboards on every working platform, and on the ends.
- Ties to the building, as OSHA and the manufacturer specify: the first at a height of 4 times the base width, then at least every 26 ft vertically for frames wider than 3 ft and every 30 ft horizontally.
- Outriggers if the tower is narrow compared with its height.
- An access ladder or stair tower.
Safety rules
OSHA requires fall protection, usually guardrails, on scaffolds more than 10 ft above a lower level, and scaffolds must be erected, moved and dismantled under the supervision of a competent person. Platforms must be fully planked, and the scaffold must support its own weight plus four times the intended load. Keep at least 10 ft from overhead power lines.
For one-day jobs on a single story, a ladder or a mobile tower may be safer and cheaper.