Arches

Arch Construction ~ by the arrangement of the bricks or stones in an arch over an opening it will be self supporting once the jointing material has set and gained adequate strength. The arch must therefore be constructed over a temporary support until the arch becomes self supporting. The traditional method is to use a framed timber support called a centre. Permanent arch centres are also available for small spans and simple formats.

Typical Arch Formats ~

Arch Cavity Tray

The profile of an arch does not lend itself to simple positioning of a damp proof course. At best, it can be located horizontally at upper extrados level. This leaves the depth of the arch and masonry below the dpc vulnerable to dampness. Proprietary galvanised or stainless steel cavity trays resolve this problem by providing:

• Continuity of dpc around the extrados.

• Arch support/centring during construction.

• Arch and wall support after construction.

Standard profiles are made to the traditional outlines shown on the previous two pages, in spans up to 2 m. Other options may also be available from some manufacturers. Irregular shapes and spans can be made to order.

Note: Arches in semi-circular, segmental or parabolic form up to 2 m span can be proportioned empirically. For integrity of structure it is important to ensure sufficient provision of masonry over and around any arch, see BS 5628: Code of practice for use of masonry.

Alternative Arch Cavity Tray

The example in steel shown...