Home & People A ease for bridges, with water or without

Press, 26 December 1979, Page 9

Home & People A ease for bridges, with water or without

LANDSCAPING AT HOME

By

Gilbert Brakey

Bridges can be used in many different situations, over water or dry stream beds, to span depressions, gullies or anv other area where there are changes of levels. the design of a bridge should be based upon tne site it is to occupy. A bridge which has been sensitively designed and placed can create a sense of drama and provide a romantic element in the landscape. The style of bridge used can range from a single log spanning a small stream to an elaborate masterpiece built of stone. The four basic types of bridges commonly used are those built from concrete, quarried stone, steel and wood. A concrete bridge can be built by the average home handyman, but all the necessary formwork needs to be carefull', set up and well braced. The construction of a concrete bridge really requires a good tradesman's knowledge in order to avoid the possible pnfalls which may occur. The stone bridge is truly bandied bv a stone ma-

son. who is a craftsman in his own right. That is perhaps unless you propose using simple rectangular stone slabs similar to that used by the Japanese in their historical gardens. A steel bridge can be light-weight, open and airy, yet provide an extremely strong structure. Where possible all steel components should be galvanised or some form of rust-proof-ing undertaken. Timber is more commonly used and w'ould be the

least expensive, while reasonably easy to work with. Timber bridges always blend comfortably with their natural surroundings. Rough-sawn timbers such as railway sleepers or even power poles provide an ideal base for the timber bridge. In certain locations dressed timber is also quite

acceptable. All timber used however should be pressure treated chemically to prevent rot. then stained. It is important to make sure that the sizes of timber used will span the distances. without any future danger of sagging. Where the ground is wet or boggy, use sturdy piers or footings of either treated timber or concrete set down to firm load-bearing ground. The minimum width for any form of footbridge is 600 millimetres, but it is preferable to have a width

of at least 1 metre so that a person crossing the bridge will feel more secure. Normally a small bridge is best without a hand-rail or at the most it needs only a very simple single rail for support. However it is most desirable to include hand-rails on any large bridge. A bridge can be of a swing type and flexible; it may be of the more rigid materials which can be built level across a stream: or it may be an arched bridge. The arched bridge

is reasonably easy to build and has the benefits of being somewhat stronger, arches being self-reinforc-ing. Bridges can provide a practical means of getting from one level to another, from one side of a stream to another, or can be built purely for aesthetic reasons. Whatever the reason for choosing to use a bridge the important point is to ensure that materials and design are in harmony with the surrounding landscape.