Deck Components and Design Considerations

A deck can be any shape you want, and in fact, simple changes like an angled corner or a 45-degree decking pattern can dress up a house with a long, plain wall. Of course, a more complicated deck is more difficult to build, and may require more materials. You can also add visual interest by wrapping the deck around a corner, adding built-in benches, integrating a fence or screen on one side, or even adding an overhead screen or roof.

Height:

On sloped ground, you may want to build your deck in multiple levels to follow the slope. Typically, wherever the deck is more than 48" off the ground, codes require that the posts be braced to prevent swaying and racking. Usually, the decking should not come closer the to within 3 " of the bottom of the access door from the house so that snow and rain does not enter the house. 

Cutouts:

A spa or hot tub can be set on the deck if the structure is reinforced to carry the weight of the water, or it can be set directly on a concrete slab on the ground, with the deck built around it. Existing trees and rocks can also be integrated into the deck by framing around them; then either cap the ends of the decking or contour the decking to the shape of the obstacle. If going around a tree, leave at least 3" on all sides to allow for growth. Around a stationary object such as a boulder, leave about 1/4" so the decking can expand and contract with temperature and moisture changes.

Railings:

Railings are the most prominent visual element in a deck, and offer great opportunity to use your imagination and creativity. They may be fastened to posts that run all the way to the ground, along the sides of the rim joists, or attached to the decking itself. They may include wood, metal, vinyl or composite

Steps and Stairs:

Step and stair construction is closely regulated by building codes. As a rule, steps and stairs should be at least 36" wide–60" if you want two people to be able to pass each other comfortably. The rise (vertical distance between steps) should be no more than 7-1/2" and the width of a tread at least 10". The slope should not be too steep–a 7" riser with a 10-1/2" tread is a common combination. Building codes will also govern how the stair is supported and attached, and whether or not you need a railing. 

Structural Components:

There are five basic components of a typical deck:

  1. Vertical posts are set in concrete or on piers set on a concrete footing. They are typically spaced 4' to 8' apart.
  2. Horizontal beams are set on the posts parallel to the decking to carry the weight of the deck.
  3. Joists are run between the beams, typically 16" apart. They distribute the weight of the deck and allow you to use decking boards that wouldn't be strong enough to span the distance between the beams.
  4. Decking is laid over the joists to form the "floor" of the deck.
  5. Railings are usually 36" to 42" high, designed so no spaces between balusters are greater than 4".

The materials used, and the size and spacing of these components, are specified by local building codes.

Materials:

Deck materials must not only be resistant to decay and insect damage, but also withstand the effects of water and sun. Standard construction lumber such as fir, pine or spruce may be treated to protect it from rot, but it won't hold up under extreme weather conditions or the ultraviolet rays in sunlight. 

You'll get much better durability by using pressure-treated pine, redwood, or cedar or IPE. Pressure-treated material is the least expensive, and can be stained to nearly any color you want. Redwood and cedar offer an added advantage in that they are soft, fine-grained woods that will resist splintering. If you use redwood or cedar, remember that only the heartwood–the reddish-colored portion of redwood or the dark brownish-orange part of a cedar board–is decay-resistant. The lighter-colored sapwood will deteriorate just as quickly as pine or spruce. IPE is the most expensive. It is a hardwood and takes longer to install, but looks beautiful.

There are also many other decking material choices including Thermally modified wood, Vinyl and Composite decking.