Floating decks can be set directly on the ground or, preferably, a bed of gravel. But it's best to support the deck on concrete blocks. This keeps the wood off the ground and away from moisture so the wood stays drier and lasts longer. You can buy special blocks designed for deck support, or you can use standard solid concrete block (the type without holes), which are cheaper and give the deck a lower profile.
What Is a Floating Deck?
Floating decks are wood decks that rest on the ground and are not attached to any structure, including your house. Also called freestanding decks, they are much easier to build than standard attached decks and typically do not require a building permit provided they are not more than 30 inches above adjacent grade.
Watch Now: How to Build a Floating Deck
Codes and Regulations
You typically do not need a building permit for a floating ground-level deck, but confirm this with your city's building department before starting your project. In some cases, you may be subject to zoning rules, which govern the size and placement of all structures on a property; your city office will provide guidance.
A deck does not need a handrail or stairs if its walking surface is under 30 inches above the ground. However, it's best to keep a floating deck as low as possible. Even a fall from a height of 12 inches, or so, can easily twist an ankle or cause more serious injury.
If you need to remove more than a few inches of soil to prepare the site for your new deck, call 8-1-1, the national "Call Before You Dig" hotline, to have all underground utility lines marked on your property. This is a free service that may take a few days, so call well in advance of starting your project.
Equipment / Tools
- Tape measure
- Carpenter's level
- Circular saw
- Drill and drill bits
- Landscape fabric and gravel (optional)
- 9 4 x 8 x 16-inch concrete blocks
- 3 1/2-inch and 2-inch or 2 1/2-inch deck screws
- 10 Pressure-treated 2x8s (10 feet long)
- 2 Pressure-treated 2x8s (12 feet long)
- 22 Pressure-treated 5/4x6 or 2x6 decking boards (12 feet long)
Prepare the Deck Area
Clear the ground where the deck will be installed, removing grass and all other organic material, as needed. Rake the ground so it is flat and level, and tamp it well with your feet or with a hand tamp tool. If desired, lay down landscape fabric over the soil and add a layer of gravel to prevent weed growth under the deck.
Set the Concrete Blocks
Arrange four concrete blocks in a rectangle so they are 12 feet apart along the long sides of the rectangle and 10 feet apart along the shorts sides, measuring from the centers of the blocks.
Position a block between each pair of corner blocks so they are evenly spaced. If desired, add one or more blocks in the center of the rectangle. This can make the deck feel a bit more solid but isn't necessary for supporting the interior joists.
Use a 6-foot level or a standard (4-foot or 2-foot) level and a straight 12-foot-long board to make sure all of the blocks are level with one another. Add or remove gravel beneath blocks, as needed, to level the blocks.
Build the Outer Frame
Clear a flat area of lawn (or use a garage floor or driveway) for building the deck frame. If necessary, you can also build the deck on top of the concrete blocks. Cut 10 pressure-treated 2x8 boards to length at 117 inches, using a circular saw or power miter saw; these are the standard joists.
Measure the two 12-foot 2x8s; if they're anything over 12 feet, trim them to exactly 144 inches (lumber often runs a fraction of an inch longer than the nominal dimension; in this case, 12 feet). These long joists are the end joists. Place the two end joists over the ends of two of the standard joists to create a 120-inch-by-144-inch rectangle.
Drill pilot holes, and fasten the pieces together with three 3 1/2-inch deck screws at each corner, using a drill. Measure from the inside of one corner of the frame and make a pair of marks every 16 inches along one of the 12-foot end joists. Do the same to mark the other end joist.
Add two more standard joists inside the frame so each end is set between a pair of layout lines, making sure the tops of the joists are flush. Drill pilot holes, and fasten through the end joist and into the standard joist with three 3 1/2-inch screws at each end.
As an option, you can use metal framing connectors, such as Simpson Strong-Tie connectors, to make extra-strong joints. Use 90-degree corner connectors at the corners, and use joist hangers where the standard joists meet the end joists. Install the connectors using the manufacturer's approved screws.
Position and Square the Deck Frame
Place the deck frame onto the concrete blocks so the frame parts rest over the centers of the blocks. Measure diagonally between opposing corners. Square up the frame, as needed, by pushing diagonally from opposing corners (this takes two people). When the diagonal measurements are equal, the frame is square.
Check the Blocks
Confirm that the deck frame is level and makes solid contact with each concrete block. If necessary, add or remove soil or gravel beneath blocks to adjust their height.
Install the Remaining Joists
Install the six remaining standard joists, following the layout lines. Remember to keep the standard joists flush with the tops of the end joists. This ensures the deck boards will lie flat.
Install the Deck Boards
Measure all of the 12-foot-long deck boards, and trim any as needed so they are 144 inches each. Place one deck board along one long side of the deck frame so it is flush with the outside face of the end joist. Alternatively, you can place the first and last boards so they overhang the end joists by 1 inch, or so, for a finished look; just be aware that you won't have the same overhang at the sides of the frame.
Drill pairs of pilot holes aligned with each standard joist, with one hole going into the end joist and one into the standard joist. Position the holes slightly off-center so they won't interfere with the frame screws. Fasten the deck board to the joists with 2-inch deck screws (for 1-inch-thick lumber) or 2 1/2-inch screws (for 1 1/2-inch-thick lumber).
Install the next deck board with two screws in each standard joist, spacing the two deck boards by about 1/8 inch apart. Install the remaining deck boards using the same techniques, spacing them evenly.
Tips for Building a Floating Deck
Pressure-treated lumber is the least expensive and most durable option for the deck frame and decking boards. For a modest upgrade, you can opt for Southern yellow pine (SYP) for the decking material, which typically has fewer knots and a better appearance than standard pressure-treated decking. Going further up the scale, there is cedar, followed by redwood. Choose these for looks only; they're not as rot-resistant as treated lumber, despite their reputation for being naturally decay-resistant. Composite decking is also an option. It is made from recycled plastic and wood pulp, and it is essentially rot-proof and requires no protective finish.
You don't have to finish the frame (if you use pressure-treated wood), but according to experts any wood decking boards should be finished with a protective deck stain or similar sealer as soon as the wood is suitably dry. If the decking is left unfinished, it will turn gray and begin to splinter in a matter of months.