Metal and Wood Pergola
In general, arches and pergolas should look at home in their surroundings. Just as the size and scale of your construction should be in proportion to that of the house and garden, so their given style should be in keeping, too. The style of a structure owes much to the material from which it is made, although very different effects can be achieved using the same materials.
While rigid rules about the style of arches and pergolas are inappropriate, one main guideline can be followed: traditional constructions tend to be ideal in gardens of period homes, while more up-to-date structures are suited to modern dwellings.
That said, there is — as with sculpture — a wonderful sense of surprise in discovering a striking, contemporary work of art on the grounds of a country home. This planned juxtaposition of styles can apply to arches, pergolas, and arbors, too, although it is really practical to introduce mixes of style only into larger gardens.
The now truly cosmopolitan aspect of garden design allows you to link the style of a pergola to that of the garden. Books, television programs, and international garden shows have ensured a burgeoning of eclectic garden styles. Anything goes. In a Mediterranean-style garden, for example, a pergola might have clean, uncluttered lines of bright-colored wood; a country garden may have a rustic oak pergola or brick pillars with oak beams; and a modern, city roof garden, with the added influence of weight restrictions, may have overhead strained wires or a light plastic pergola.
Style is about individual choice. Have what you wish, but remember that the most successful constructions are always based on sound design principles rather than short-lived trends.
Wood — the most common medium for arches and pergolas — is available in many forms. Treated softwood is used widely for both posts and beams and is usually supplied as rough-sawn lumber. Planed lumber is smoother, ready to be painted with a choice of colored wood stains.
Hardwoods, particularly oak, are more durable and weather attractively to look especially good with older houses. Such woods tend to be more expensive. If they are your choice, make sure the wood has been sourced from sustainable, managed forests.