Tools and Materials

Note

Product costs, availability and item numbers may vary online or by market.

Before Beginning

A backyard lawn and a tree in front of a wood panel fence.

In the location we’re building this floating deck, because it’s not attached to the house and will be less than 200 square feet, we don’t have to go below the frost line — the level at which water in the soil typically freezes — for our foundation. Check with your local building department to see the requirements for your area and your deck. In addition to requirements for foundations and placement, you’ll find out about factors like any permits and inspections that are required, size limitations and more. In addition, find out if your homeowners association has any rules or guidelines that could impact your plans.

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Caution

Before beginning any excavation, call 811 to check for underground utilities.

Good to Know

Building a floating deck involves working with heavy, unwieldy materials. Enlist a helper.

Floating Deck Plan and Layout

A diagram of the foundation and frame of a floating deck with stairs built around a tree.

The plan for this deck is to use paver base and concrete deck blocks for the foundation. The 2-inch-by-6-inch joists will rest on top of the blocks. Cap blocks on paver base will support the step section. This deck will have composite decking with fascia boards around the perimeter to cover the frame and give it a finished look. The deck is going to be low-lying — it’ll be about 12 inches above the ground when complete.

Good to Know

If you already have your deck laid out, you can move to the next part of the How to Build a Floating Deck Series: Framing a Floating Deck.

Instructions

A man tying mason line onto a batter board to mark the layout of a deck.

Assemble batter boards from furring strips and landscape stakes. Drive them into the ground — two at each corner — just outside of the deck layout. Tie mason line between opposing batter boards, making sure the lines are tight. The intersections of the batter boards mark the corners of the deck frame.

Good to Know

This deck will have steps near a patio. To make sure the layout allows room for the steps, we measured in from the sidewalk the depth of the steps section and marked one of the batter boards for the line that'll represent the deck edge that runs parallel to the sidewalk.

A man marking a stake at the corner of a deck layout.

Once the batter boards and strings are in place to mark the layout and dimensions, make sure the layout is square. Using the 3-4-5 method is an easy way to do this. Starting from a corner, measure 3 feet along on one string and make a mark. From the same corner, measure 4 feet along the adjacent string and mark. Measure between the two marks and adjust the strings until the diagonal measurement equals 5 feet. Once it does, the corner is square. Repeat with the other corners and mark each squared corner with a small stake at the intersection of the lines.

Mark the lines for the deck blocks that'll support the beams. Drive stakes into the ground along the two opposite mason lines to mark the ends of each row (where the end of each beam will be located). For this deck, the deck blocks will be in three parallel rows. The first row will be about a foot from the front edge. There’ll be a row in the middle and a row near the back edge.

Caution

Make sure you’re using the right fastener for the hardware, materials and application. Some hardware, such as joist hangers and other structural pieces, require specific fasteners. Some materials, such as treated lumber, require specific fastener finishes or materials.

Creating the Deck Foundation

Now that the deck is laid out, you can begin clearing the deck area and setting your concrete deck blocks. For our deck, we’ll use blocks near the end of each joist and a few to hold up the center beam. You can also go without the center beam and use more blocks under each floor joist for additional support.

Concrete deck blocks are great alternatives to concrete foundations. They support the deck frame above the ground and can hold your framing members horizontally, or they can vertically support posts for a higher deck. Always check your local building codes for foundation requirements.

Instructions

A man using a Craftsman level and tape measure to determine the height of a board on a deck block.

Make sure the ground will support the deck at the correct height. Our deck will be about 12 inches above the ground, so we’re going to build the frame to that height. Set a scrap piece of the lumber you’ll use for the beams in place on a deck block resting on the ground. Place a 48-inch level on top of the lumber, extending out over flat ground, a nearby patio or sidewalk, and adjust until it reads level. Measure up from the ground to the level. This will give you an idea of how close you are to the correct height. You’ll adjust later to get the blocks at the right height.

A man using a level and a board to confirm a middle block is level with the front and back blocks.

With the four outside corner blocks set and level, place and check the middle perimeter blocks. Fit a board between the two 2-inch-by-6-inch boards at the front and back, and set it in place on the three blocks. If the center block is too high, remove the board and wiggle the block to set it deeper in the paver base. If the center block is too low, add paver base to raise it. Check for level. Repeat for the other side of the deck to set all of your perimeter blocks at the right level.

Next Steps: Building the Deck Frame

A man placing a flooring joist on a deck block and in a joist hanger.

With the layout complete, you're ready to begin constructing the frame for your floating deck. The frame will be constructed of 2-inch-by-6-inch pressure-treated lumber. See the next part of the How to Build a Floating Deck series: Framing a Floating Deck.

Planning a Floating Deck

Tools and Materials

Tools

Materials

Before Beginning

Floating Deck Plan and Layout

Instructions

Creating the Deck Foundation

Instructions

Next Steps: Building the Deck Frame

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