How to Build a Redwood Deck
Warm weather always seems to bring out deck builders. So, we thought it would be an appropriate time to offer a few valuable tips on the subject.
As with all good construction, the quality of a wood deck begins with the integrity of its’ concrete foundation. Although there are only a few basic types of foundations it is always a good idea to check with an engineer just to make sure the type you intend to use is adequate. Deck foundations normally consist of a combination of pre-cast concrete pier caps supported by poured-in-place concrete footers. The footer is simply a hole in the ground filled with concrete. The size and depth of the footer depends primarily on prevailing soil conditions. Where footer dimensions will vary, the pre-case pier cap is a standard hardware item that is readily available. For best results carefully level each pier cap before the supporting footer concrete dries. Oh, and don’t use fence post concrete for the footer. It isn’t as strong as regular concrete mix. And don’t rule out mixing your own concrete from scratch. Concrete mixes: Strong, 6 Bags Cement, 14 c.f. Sand, 18 c.f. Stone 1:2 1/4:3 Moderate, 5 Bags Cement, 14 c.f. Sand, 20 c.f. Stone 1:2 3/4:4, Economy, 4 Bags Cement, 13 c.f. Sand, 22 c.f. Stone 1:3:5
If your deck will be constructed on a hillside be absolutely sure to consult an engineer.
The floor framing can consist of girders supported by piers or floor joist supported by girders and piers. Girders double as floor joist when there isn’t enough room between the earth and the decking for two layers of framing. The larger girders require fewer piers than floor joist but because of their larger size are not as cost effective as the smaller floor joist. Cost effective or not girder framing may be your only choice. Fortunately, girders can be used at less frequent increments than floor joist. That is, where floor joist are used at 16- or 24-inch centers the more expensive girders can be stretched out to as much as 4-feet apart. We like the girder joist combination — if you have the room (and the budget). Keep in mind that the deck frame will be exposed to the elements and should be assembled with fasteners that are coated to prevent rust and corrosion. Pressure treated fir or pine are both good choices for the floor framing.
We feel good about using pressure treated material for the framing parts. But, we prefer to use either Cedar or Redwood for naturally finished surfaces such as the decking and rails. However, pressure treated Southern Yellow Pine is OK if a painted finish is desired. Cedar and Redwood contain natural resins that resist insect attack and moisture damage and are provide a luxurious natural wood look. If you like the Knotty Pine look you may want to consider Alaskan Yellow Cedar. Yellow Cedar looks like Knotty Pine, but is weather resistant where Pine is not. For deck joist that are spaced 16-inches apart, 1×4 or 1×6 decking can be used. If the joist are 2-feet apart then 2×4 framing is needed. 2×6 decking will span up to 4-feet. By the way, if Redwood is the chosen material consider using Construction Heart Redwood. It’s desirability stems from the fact that is moderately priced and reasonably knot free.
Here is an important tip that will help to reduce wood rot. Remember: wood rots when it remains wet for long periods of time and wood-to-wood connections have a tendency to retain water – wet wood equals rotten wood. Eliminate wood-to-wood connections by insulating them with strips of 15- or 30-pound roofing felt. Staple a strip of felt to the top edge of each floor joist so that the felt insulates the joist from the deck covering. By preventing the two wood surfaces from coming into direct contact water retention – and accompanying wood rot – is minimized. Insulating material is not required when hidden deck fasteners are used. Hidden fasteners not only provide a clean look they also provide an space between the joist and the decking insuring a connection that will dry almost as quickly as fully exposed surfaces.
It may be interesting to note that when decking is installed at other than right angles to the joist there can be as much as 20% waste. We don’t recommend against installing decking at an angle, but we do want you to know that there is some additional labor and material cost involved.
Handrails are required for safety when a deck is 30” (or more) above ground. Conversely, handrails also can be used to divide (and define) areas within a deck or to separate the deck from other areas of the landscape — regardless of ground clearance. In any event, it is important to check the current building code when preparing to build handrails. The building code defines how much weight a handrail must resist to qualify as a safe rail. The code also specifies the maximum space allowed between rail surfaces (horizontal or vertical).
If you need help constructing a deck there are a couple of great resources that offer inexpensive planning tools. The California Redwood Association has created a deck building kit that includes everything needed to design a deck including instructions, deck and furniture templates, graph paper, and even construction details drawn to scale. Contact the CRA by dialing 1-888-CAL-REDWOOD.