Once you have determined the basic design of your deck, the next step is to choose your materials. The most common choices are pressure-treated (P/T) lumber (usually Southern pine), redwood, or cedar. As a rule, pressure-treated lumber is the best choice for the substructure; the species you use for the visible parts of the deck will depend on your budget and the look you want.

The span tables in this document will help you determine how much material you need, based on the species you choose. Although there is no such thing as an "average" deck, these instructions assume that your deck is attached to the house, is no more than 6" off the ground, and has no special load requirements. All design recommendations below are suggestions only, for estimating purposes. Always check local building codes before determining the final design.

Inside this document you will find information about:

• Choosing Materials
• Preparation and Layout
• Building the Substructure
• Decking and Railings

CHOOSING MATERIALS

• Decking–If you choose pressure-treated lumber, you'll have a choice between 5/4 x 6 decking (1x5-1/2 actual size) or 2" material (typically 2x4 through 2x8, all 1-1/2" thick). The size and species of the decking you choose will determine the spacing between your joists. Recommended spacing for common decking boards is as follows:
  
  

  Decking	Joist Spacing
  5/4x6 P/T Southern pine	16" maximum
  2 inch thick redwood, western red cedar, S-P-F, Hem-fir, Northern white cedar	24" maximum, 16" preferred
  2-inch Southern pine	24" maximum

  
  
  
• Determining Joist Size–2x6s through 2x10s are the most common sizes used for joists. The beams that carry them are typically 4x6 through 4x10, often "built up" from doubled 2-inch lumber. Pressure-treated lumber is generally less expensive than redwood or cedar, and can be used for the substructure even when the decking and railing will be other species.
  
  
• In most cases, you'll want to determine the spacing between beams first, then use a joist size appropriate to that spacing. If the deck will be no more than 6' off the ground, a common recommendation is to space the support beams no more than 12' apart. As a rule, you'll only need one beam along the outer edge of the deck (a ledger bolted to the house supports the other end of the deck).
  
  

  Beam Spacing	Joist Size (joists 16" o.c.)
  Up to 8 feet	2x6 (Southern pine, Douglas fir, Western red cedar, S-P-F, or Hem-Fir) 2x8 (redwood, Northern white cedar)
  8 to 10 feet	2x8 (all species listed above)
  10 to 12 feet	2x8 (Southern pine, Douglas fir, Western red cedar, S-P-F, or Hem-fir) 2 x 10 (redwood, Northern white cedar)
  Beam Spacing	Joist Size (joists 24" o.c.)
  Up to 8 feet	2x6 (Southern pine, or Douglas fir) 2x8 (Western red cedar, S-P-F, Hem-Fir, redwood, or Northern white cedar)
  8 to 10 feet	2x8 (all species listed above)
  10 to 12 feet	2x8 (Southern pine, or Douglas fir) 2x10 (Western red cedar, S-P-F, or Hem-Fir, redwood, or Northern white cedar)

  
  
  
• Determining Beam Size–Since support posts are often run through the decking to serve as railing posts, the specifications below are given for posts that will be spaced no more than 6' apart, with beams that are no more than 12' apart. With these spacing specifications, 4x4 posts are adequate for any deck less than 6' off the ground.
  
  

  Beam Spacing (round down to nearest foot)	Miniumum Beam Size (doubled 2" material may be used in place of 4" thickness)
  Up to 6 feet	4x6 (Southern pine or Douglas fir) 4x8 (Western red cedar, S-P-F, Hem-Fir, redwood, or Northern white cedar)
  Up to 7 feet	4x8 (all species listed above)
  Up to 9 feet	4x8 (Southern pine, Douglas fir, Western red cedar, S-P-F, or Hem-Fir) 4x10 (redwood, Northern white cedar)
  Up to 11 feet	4x8 (Southern pine or Douglas fir) 4x10 (Western red cedar, S-P-F, Hem-Fir, redwood or Northern white cedar)
  Up to 12 feet	4x10 (all species listed above)

  
  

FIG. 1 - Ledger and joist connections.

FIG. 2 - Use the equal diagonals method to square your layout.

FIG. 3 - Post, pier, and footing detail. The footing must extend below maximum frost depth.

PREPARATION AND LAYOUT

• Preparation–First, prepare the ground under the deck by removing the sod. Slope the ground away from the house a minimum of 1" every 15' to provide drainage. Once the deck is finished, the ground should be covered with 6 mil. black polyethylene to keep weeds from growing.
  
  
• Measure and mark the position of the ledger along the wall. The height of the ledger should be 1" below the bottom of the door plus the thickness of the decking, plus the depth of the joists if you plan to set the joists on the ledger and beams rather than using joist hangers. It makes no difference which way you set the joists, as long as your layout is consistent.
  
  
• Mount a 2x6 ledger to the wall with 1/2" lag screws. The ledger must be level, and the lag screws should be long enough to penetrate the studs at least 3". Use two lag screws at each end, and one at each wall stud (typically 16" on center) in between. Install a "Z"-shaped flashing above the ledger to shed water, or space the ledger away from the wall with washers (Fig. 1).
  
  
• Layout–To establish the outside perimeter of the deck, measure out from each end of the ledger about 18" beyond the outside edge of the deck. Set up batterboards (Fig. 2) as shown, then run taut strings from each end of the ledger to the batterboards to establish the sides of the deck.
  
  
• Run a third string between the batterboards to establish the outside edge of the deck. Square the layout by measuring the opposite diagonals, then adjusting the ledger-to-batterboard strings until both measurements are equal. Take care to maintain the correct distance between the strings.

FIG. 5 - A sample joist assembly.

FIG. 6 - To splice joists, lap them at least 12" and nail them together with galvanized nails.

FIG. 7 - Use blocking between joists over beams and wherever required by local building code.

BUILDING THE SUBSTRUCTURE

• Footing and Piers (Fig. 3)–Use a plumb bob from the string to establish the location of the footings. The holes for the footings must be deeper than the maximum frost penetration in your area, and deep enough to rest on undisturbed soil. It's a good idea to dig 6" deeper and fill the bottom of the hole with gravel to allow drainage.
  
  
• Mix concrete and pour the footings. To find the number of 90# bags of ready-mixed concrete you'll need for each 12x12 footing, measure the depth of the footing in inches and divide by 8. As you finish each pour, set a precast pier on the footing so it extends about 6" above the ground level. Use a thin cement mix to bond the piers to the footings.
  
  
• Posts–After the concrete has set, stand the posts on the piers. Use temporary braces and a level to plumb the posts. Once the posts are set, run a mason's line from the top of the ledger to each post and use a line level to mark it for cutting. The height of the post should be equal to the height of the ledger minus the depth of the beam that will be set on it.
  
  
• Beams–Fasten post-to-beam connectors on top of the posts with nails and 1/2"x5-1/2" hex bolts, then set the beams into the connector. Plumb and square the assembly, then secure the beams as you did the posts. If local building codes require it, install 2x6 diagonal cross braces and secure them with 1/2"x4-1/2" lag screws (Fig. 4).
  
  
• Joists (Fig. 5)–Mark the joist locations on both the beams and ledger, either 16" or 24" o.c., as per your design. Set the joists in place with the crowns up. If the deck is wide enough that you need two sets of joists (and if you set the joists over the beams rather than hanging them from joist hangers), splice the connections by overlapping each pair of joists at least 1' and nailing them together with 8d galvanized nails (fig. 6). Install blocking between the joists wherever required (Fig. 7). Blocking requirements are determined by your local building codes. Finally, nail the rim joist across the ends of the joists.
  
  
• Stairs–Build any stairs you will need. Instructions for building outdoor stairs are covered in an accompanying brochure.

FIG. 8 - When you lay the decking, keep the bark side of the deck boards up, make sure all joints are supported, and stagger the joints for a cleaner appearance. If you use nails, angle them toward the center to keep the board from twisting.

FIG. 9 - You can use nails, screws, or clips to fasten deck boards. All fasteners must be either galvanized, stainless steel, or aluminum to prevent rust and staining.

DECKING AND RAILINGS

• Decking–Deck boards should be laid with the bark side up (fig. 5), and with both ends centered over a joist. Stagger the joints of side-by-side deck boards so they don't line up. Notch the boards around posts or other obstructions, leaving 1/8" space for drainage.
  
  
• 2"-thick deck boards should be spaced approximately 1/8"; most builders set a 16d nail between the boards as they fasten them. 5/4"'x6" pressure-treated decking may be placed with each board flush against the next; natural shrinkage will provide the proper spacing.
  
  
• Fasten the deck boards at each joist (Fig. 8). Use two fasteners per support point for decking up to 6" wide, or three fasteners for wider boards. Deck screws or clips are generally better than nails, but all fasteners must be hot-dipped galvanized, aluminum, or stainless steel (Fig. 9). If you use nails, blunt the points by tapping them with your hammer, to avoid splitting the decking.
  
  
• Let the decking run over the edge of the structure, then saw the ends off after all boards are laid.
  
  
• Railings–Secure the railing posts at each corner of the deck, and on each side of the stairs. Then secure the field posts, spaced equally between the corners but no farther apart than allowed by local building codes (typically 6'). Nail the sub-railings and cap rail in place, then add the balusters.

Ask for Other "Show-How" Instruction Sheets
Additional easy-to-use instruction sheets for home do-it-yourself projects are available from your local supplier of materials. Come in and ask for "Show-How" instructions when you get ready for that next handyman project!