Pergolas are among the oldest known gardening structures. Dating back to ancient Egypt, these lovely climbers were used to cover walkways from one area of a house to the next. Structurally, a pergola is a series of posts with a flat roof. Unlike an arbor, pergolas are meant for transitional purposes such as connecting buildings and leading to gardens. Pergolas must be structurally sound enough to support the desired climbing plants such as grapes, pomegranates, roses or ivy.
Verify the overall height requirements from the homeowner's association, and obtain approval for the project if necessary.
Pick the area the pergola will cover. Measure the area and verify its overall stability. If necessary, determine where proper foundations such as pavement or stones will be placed to ensure the structure holds and maintains its shape.
On a piece of graph paper, plot out the overall design, including details such as the number and thickness of support posts and how much of the structure will hang out from the posts. Consider obtaining some pictures of various pergolas to provide ideas for the overall shape and design. Websites such as gardenstructure.com provide visual pictures for the designs they sell, which can be very helpful when designing one's own. If desiring more detailed examples, go to flickr.com and enter "pergola" in the search field. Hundreds of pictures of garden pergolas from around the world are available for viewing.
Determine the desired building material for the pergola. Pergolas were traditionally made of wood; however, they are also available in plastic. If desiring to place fruit-producing climbers on the pergola, it is better to consider wood because its overall structure is stronger. On the other hand, remember that all the wood being used in the project must be treated to ensure it does not rot, and will need to be maintained annually, especially in areas of snowfall.