Begin the simple design of this freestanding basic deck by accurately laying it out.
The simple design of this deck includes several fail-safe features. (For instance, the beams may be off by an inch or so without weakening the structure.) Don't take the project lightly, however. Produce an accurate scale drawing and get it approved by your building department. Keep in mind that the decking will overhang the joists by 1-1/2 inches or so on all sides.
Planning the footings and beams
Because they extend 3 feet beyond the footings, massive beams made of three 2x10s are required. Large beams call for larger-than-average supports -- 4x6 posts and 12-inch-diameter footings.
Four to five hours to build batterboards, figure the layout, stretch lines, and determine footing locations
Drill, sledgehammer, tape measure, mason's line, carpenter's square, shovel
Measuring and checking for square, fastening with screws, pounding stakes
Get drawings approved and double-check them for accuracy, study the way the deck will be assembled
1x4 or 1x2 for stakes, 1-5/8 inch screws, masking tape
Measure out from the house for the position of a post and drive in another batterboard. Position all batterboards about 2 feet beyond the post locations. To keep your estimated post locations roughly perpendicular to the house, hold a carpenter's square against the house and run a tape measure along its side, as shown.
Drive a screw partway into the middle of each batterboard's crosspiece. Stretch mason's line to form a grid. Use the screws to anchor the string. The mason's lines should intersect at roughly the same height. Drive one of the batterboards deeper into the ground, if necessary, to align the lines.
Check the mason's lines for square. Measure 6 feet along one line and mark the spot with a piece of tape. Measure 8 feet along the perpendicular string line and mark it the same way. (Make sure you know which side of the tape indicates the exact spot.) Measure the distance between the two marks; if it is exactly 10 feet then the lines are square to each other. If not, adjust one line. With this method you can substitute 6, 8, and 10 with any multiples of 3, 4, and 5; for example 9, 12, and 15; or 12, 16, and 20. The larger the numbers, the greater the accuracy.
To make a two-level deck, you can build two decks as shown in this chapter. Another way to do it is to let the beam of one section serve as the rim joist or header for the other.
Set the posts, but build your beam from two 2x boards fastened to opposite sides of the posts. This gives you essentially two headers at the same level. (You could consider them rim joists, too, if you want to change the decking orientation.) Build frames on both headers and hang joists in the section that will be the lower deck. Don't hang joists in the other section; instead build a frame on top of it and hang the joists in this raised platform. Repeat for multiple levels.
This method requires you to lay out the sections with separate sets of batterboards.
Laying out a large deck calls for the same techniques as laying out a small one, but is slightly complicated by the length of the sides and by the necessity of keeping the line posts (those set between the corner posts) lined up.
Set your batterboards firmly in the ground and tie the mason's lines tightly onto the crosspieces so they don't sag or move around in the wind.
When you square the corners with a 3-4-5 triangle, use larger multiples of 3, 4, and 5, such as 6, 8, and 10 or 9, 12, and 15. When the sides of the deck are long, the larger numbers will keep your measurements more accurate. Measure the diagonals of the site as a final check, and adjust the lines if necessary.
To mark the center of a posthole, hold a plumb bob (a chalk line will work in a pinch) with its string barely touching each layout line. Drive a stake or landscape spike into the ground to mark the spot.
If the design calls for three or more posts supporting the same beam, the middle posts do not require intersecting string lines. Just measure along the line or use a spacing jig to mark the center of the footing.