How to Lay Out a Deck

The first step in building a deck is to lay it out. We'll show you how to do so accurately.

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Accuracy is crucial when laying out a new deck. You wouldn't want all of your hard work to be thrown off by a few wrong measurements. That's why it's important to lay out the deck before you start building. You'll have the chance to check—and double check—all of your measurements before you begin. 

To make the process even simpler, we've designed a deck with several fail-safe features. The beams, for instance, may be off by an inch or so without weakening the structure.

Before you begin, 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.

You'll also need to plan out 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. 

Expect to spend four to five hours building batterboards, figuring out the layout, stretching lines, and determining footing locations. To lay out the deck, you need to be able to measure and check for square, fasten screws, and pound stakes. It's also a good idea to double-check your drawings for accuracy once they've been approved, and to study the way the deck will be assembled.

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What You Need

  • Drill
  • Sledgehammer
  • Tape measure
  • Mason's line
  • Carpenter's square
  • Shovel
  • 1x4 or 1x2 for stakes
  • 1-5/8 inch screws
  • Masking tape

Step 1: Construct Batterboards

Construct batterboards using 1x2s or 2x4s and a 1x4 crosspiece. Stakes can be 16 to 36 inches long. If the ground is hard, make them shorter; if soft, make them longer. Cut the crosspieces about 30 inches long. Assemble the pieces with a single screw at each joint.

Step 2: Mark the House

Mark the house wall for the positions of the posts. First mark the outside of the framing (the decking will overhang it by 1-1/2 inches). Then measure over and mark where the post will be located. Make sure you identify the center of the post.

Then drive a batterboard into the ground near the house, more or less centered over the post location. Pound the stakes until the crosspiece is 6 inches or so above the ground and stable. For soft, wet soil, use long stakes; shorter stakes are fine for hard ground.

Step 3: Install Batterboards

Then drive a batterboard into the ground near the house, more or less centered over the post location. Pound the stakes until the crosspiece is 6 inches or so above the ground and stable. For soft, wet soil, use long stakes; shorter stakes are fine for hard ground.

Step 4: Position Batterboards

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.

Step 5: Plan Post Locations

Estimate the location of the other posts. Place additional batterboards 2 to 3 feet beyond the post locations. You can approximate the footing locations by driving temporary stakes into the ground.

Step 6: Form a Grid

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.

Step 7: Adjust and Anchor Line

Adjust the line that runs parallel to the house until it is equally distant from the house along its entire length and lined up with the center of the footings. Anchor this line firmly to its batterboards so you won't bump it out of position.

Step 8: Check for Square

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.

Step 9: Mark Position

Once you have found the correct position for the line, mark its position on a batterboard with a pencil. You can remove the screw and drive it under the line or leave the screw in place. Just make sure you wrap the line tightly on the mark and tie it to the screw.

How to Locate Piers

Batterboards support strings that help pinpoint the center of each post and pier. In this case, the piers are positioned 3 feet from the house to avoid the backfill next to the foundation of this new house.

How to Locate Posts

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.

How to Lay Out a Two-Level Deck

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.

How to Lay Out a Large Deck

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.

After you mark the location of the corner posts, lay out and mark the line posts. Use a template to keep them spaced properly, driving stakes or landscape spikes to mark them.

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