Dear Friends
THE LAW REQUIRES THAT NO SCAFFOLD SHALL BE ERECTED, MOVED, DISMANTLED OR ALTERED EXCEPT UNDER THE DIRECT SUPERVISION OF A COMPETENT PERSON.
Scaffolding is a specialization.
There are more than 30 different types of scaffolds. Scaffold can be supported, under-hung , hanging or bracket supported.
Materials used are bamboo, aluminium, fiberglass and steel.
Common scaffold are tube and coupler, system and welded frame. Welded frame scaffold are only for light duty.
OSHA standards which are widely adopted give the load capacities which are already given by hseofficerjsk.
Details on ground preparation, sole boards, base plates, Post spacing, bracing requirements, guard rails and toe boards are all given in the standards for light duty and medium duty scaffolds.
With prescribed post spacing the scaffold height in this case can be up to 125 feet.
Only for independent, tower and mobile scaffolds the 1:4 (1 base width to 4 height) ratio is applicable. You can increase the height of scaffolds by using suitable ties, gay wires and rakers. However this is applicable for scaffold up to a height of 40 feet. Beyond this height the scaffold should be designed by a structural engineer.
Heavy duty scaffold should only be designed by a structural engineer. There can be dead load and live load on scaffold. Though the construction method is same, post spacing and bracing will differ depending up on loads.
Weight of all the scaffold components plus the intended load will have to be considered in assessing the load on a scaffold. A factor of safety of 4 is required for any scaffold.
Regards,
Kesava Pillai