Fig. 37
Hollow towers are erected or repaired in the same manner as chimney shafts, except that climbing ladders are not often required. External or internal scaffolds may be erected. Towers being usually of larger area than chimney shafts, the putlogs for internal scaffolding are often of short poles from 6 to 8 inches diameter. Even these may require extra support. This is gained by carrying standards from the ground level or other solid foundation and tying to the putlogs. If of great height the standards may be unable to carry their own weight. For the cases where danger might be apprehended from this cause, [fig. 37] shows a system of framing, which, being supported by the set-back in the thickness of the wall, will carry the upper standards.
Steeples are generally built by the aid of external scaffolds, which, as in the case of chimney shafts, should be well braced. The lower portion may also be repaired in this way, the standards rising from the ground level, or, if so designed, from the top of the tower. A series of needles could be arranged for the higher portions.
Fig. 38
Domes and arches.—The scaffolding for domes and arches consists of a series of standards standing upon the area covered by the building, and connected by ledgers and braces in directions at right angles to each other. The platform is laid on the top ledgers.
When the building is of large span square timbers are often used, balks for standards and runners, and half timbers for struts and braces.
[Fig. 38] shows a design for repairing roofs and arches where a roadway has to be kept below.
Swinging scaffolds. Painters’ boats or cradles.—Painters’ boats are useful scaffolds for the repair of buildings, more especially where the work is light. [Fig. 39] shows the general construction. They are suspended from jibs, fixed usually on the roof for outside work, and by means of blocks and falls they can be moved in a vertical direction by the workmen when in the boat.
