How to Design a Deck Building Plan

Draw on paper your existing house plan to scale using a pencil, architectural scale, and T square. An architectural scale allows the designer to draw architectural elements at a ratio smaller than true scale to accurately represent an object or structure. The word "scale" refers to both the measuring instrument and the drawing's ratio to true scale. The scales used for drawing include 1/16 inch equals 1 foot, 1/8 inch equals 1 foot, and 1/4 inch equals 1 foot. Whatever scale you choose to work with, remember to use this scale throughout the drawing, so there are no inconsistencies with the drawn elements.

Determine the design of the proposed deck. Decks should be at least 8 feet deep to allow people to sit comfortably, however the optimal depth of a deck is 12 feet deep. Decks can have multiple levels, and the horizontal surfaces can be made with a number of different types of decking. For example, you can use tongue and groove decking, diagonal decking, cement board decking, as well as the traditional wood 5/4 board decking. Keep in mind tongue and groove decking must have a slope to drain rainwater. The other types of decking require 1/8 to 3/16 gaps for drainage.

Also, determine whether you would like to have any enclosure on the deck. Possible shading and enclosure devices include trellises or pergolas, latticework partitions and awnings. In addition, think about the furniture you would like to place on the deck.

Draw the proposed plan of the deck on the existing house drawing, and draw the furniture layout you plan to place on the deck. Use the same tools as those for the existing house drawing. Compare your existing house and proposed deck plan to the proposed space aside to your house where the deck will go. Note any of the ground's elevation changes and compare these to the height of the proposed deck.

Draw a handrail, on your plan, anywhere your deck surface is 30 inches or higher above the ground surface. If you would like to provide stairs to access the deck from your property, measure the distance between the ground surface and the proposed height of the deck. Then, determine the height of your proposed stair risers; stairs should be between 4 and 7 3/4 inches. Divide your deck height above the ground by your stair height--this is the total number of stairs you will need. For example, a deck 30 inches above the ground with 6 inch risers will require 5 risers. The stair treads are proportional to the riser height, so the height of two risers plus one tread equals 24 to 25 inches. In the example above, two risers equals 12 inches, so the tread should be 12 to 13 inches. Remember to draw handrails for the stairs if there are more than two stair risers to reach the deck surface.

Draw the location of the supporting deck posts. Posts are usually provided at the corners of the deck and in a grid across the deck surface with spans no greater than 12 feet. Longer spans are possible, but 12 feet is a safe distance to use.

Draw doubled 2-by-12 beams to connect the grid of deck posts, and draw 2-by-10 joists running in one direction, 16 inches on center, between the beams.