Redwood Empire is proud to provide a few tips on how to properly design and create the perfect Redwood deck.
The quality of a wood deck begins with the integrity of its concrete foundation. Check with an engineer to make sure that the type of foundation you select is adequate. This is especially true for hillside projects. Deck foundations normally consist of a combination of pre-cast concrete pier caps supported by poured-in-place concrete footers. (Pier caps resting on dirt don’t last.) The footer is simply a hole in the ground filled with concrete, and its size and depth depends on soil conditions. Whereas footer dimensions will vary, the pre-cast pier cap is a standard item that is readily available at most home-improvement centers and hardware stores. For best results, carefully level each pier cap before the supporting footer concrete dries. Uniform pier height is not important. The wood posts that are between the pier caps and the floor frame are used to compensate for any differences.
Don’t use fence-post concrete for the footers; it isn’t as strong as regular concrete mix. And, don’t rule out mixing your own concrete from scratch. It is easy to do. Concrete consists of cement, stone (rocks) and sand. The ratio for a really strong mix: one part cement (we like portland), two parts rock and three parts sand (anything but sea sand will do concrete and salt don’t mix). This concoction is known as six-sack mix because, when the combined ingredients total one cubic yard (by volume), the mix contains exactly six sacks of cement.
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. Girders by themselves can be used as the primary floor frame, but to be cost-effective, they must be spaced farther apart than regular floor framing, resulting in a bouncy floor. Tightly spaced floor joist atop widely spaced girders produce a sturdier floor.
Typically, the floor joist used above girders are spaced at 16 or 24-inch centers. When girders are used in lieu of floor joist they are spaced at 32 or 48-inch centers. If closer than 32 inches, too many piers are needed and if farther apart than 48 inches, common 2x6 decking is over-spanned.
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 good choices for the floor framing.
We like pressure-treated material for the framing parts, but prefer to use either cedar or redwood for finished surfaces such as the decking and rails. Pressure-treated material is OK if a painted finish is desired. Cedar and redwood contain natural resins that resist insect attack and moisture damage, and provide a luxurious natural wood look. If you like the knotty-pine look, consider Alaskan yellow cedar. It looks like knotty pine, but is weather-resistant, whereas pine is not. For deck joist that are spaced 16 inches apart, 1x4 or 1x6 decking can be used. If the joist are 2 feet apart, 2x4 framing is needed. 2x6 decking will span up to 4 feet. If redwood is your choice, consider construction heart redwood. It is moderately priced and comparatively knot-free.
A tip that will reduce wood rot: Wood rots when it remains wet for long periods of time. Wood-to-wood connections have a tendency to retain water. Wet wood means rotten wood. Eliminate wood-to-wood connections by insulating them with strips of 15 or 30-pound roofing felt. We like to staple a strip of felt to the top edge of each floor joist to insulate 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. Another way to reduce rot is by using hidden deck fasteners. They provide a space between the joist and the decking that allows air flow at every connection. Hidden deck fasteners eliminate the need to drive nails through the top of the decking.
When decking is installed at other than right angles to the joist, there can be as much as 20 percent waste. We don’t recommend against installing decking at an angle, but we want you to know that there is some additional labor and material cost involved.
Use these tips to ensure a great build and even better results.