How to Build a Floating Deck

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A floating deck can add visual interest to an otherwise mundane yard and provide a smooth surface above grass-dwelling insects that's ideal for entertaining. They look expensive and custom, but a two-person team could easily build a floating deck over the course of a few weekends – given the right tools, materials and plenty of patience. To make the process easier, plug in your desired dimensions into any deck designer website and receive a custom report on everything you'll need to complete your floating deck.

How to Build a Floating Deck
Image Credit: irina88w/iStock/GettyImages

Gather Your Tools and Materials

To start the project, you will need a shovel or auger, a level, a drill and rill bits, grass-safe spray paint and a gravel. You also should have 10 concrete deck blocks, 10 6-by-6 pressure-treated posts that are 2 feet long, three 2-by-10 pressure-treated beams that are 16 feet long, 15 2-by-8 long pressure-treated joists that are 16 feet long, 34 1-by-6 deck boards that are 16 feet long, 20 steel post caps, 22 2-by-12 joist hangers, 35 3-inch countersinking deck screws and 350 3-inch flathead stainless steel deck screws.

Prep the Ground

First, figure out your deck size. Factor in any furniture or outdoor appliances you want to keep on the deck and keep their dimensions in mind. For example, the materials listed above are sized for a square, 16-foot-by-16-foot floating deck. Once you've determined the area it will cover, mark off the outline in your yard using grass-safe spray paint.

Install the Posts

Use spray paint to mark an "X" where the concrete blocks and posts will go. A 16-foot square deck, for instance, would require 10 posts arranged in three rows: Three posts spaced approximately 7 feet, 3 inches apart on the right, four posts spaced approximately 4 feet, 9 inches apart in the middle, and another row of three posts spaced 7 feet, 3 inches apart on the left. The three rows of posts should be evenly spaced 7 feet, 3 inches apart, with the first and last posts in each row parallel. Depending on the deck height you want, dig holes 2 to 3 feet deep using a shovel or an auger, which you can rent from a home improvement store.

Pour a layer of gravel into the holes before placing concrete blocks to allow for water drainage when it rains. Next, add the concrete deck blocks. Make sure they're a size that will hold your posts snugly. Place posts into the blocks vertically.

Alternately, you could pour concrete into the holes and set the posts that way. Once posts are secure, place a flat board over one row and use a level to ensure posts are of equal height. Repeat this process for each row of posts.

Add Support Beams

Drill metal post caps, which will hold the support beams, onto the tops of each post. Standing the 2-by-10 beams so that they are 10 inches tall, place one on each row of posts from left to right. Once you've laid the first beam, use a level to make sure it's parallel to the ground, then secure it to the post cap using a drill. Repeat these steps for the next two beams.

Layer on Joists

Next, attach the 2-by-8 boards, or joists, on top of the support beams. Place them so they're 8 inches tall and perpendicular to the beams. Start with the outermost joists first using post caps, a drill and decking screws to attach them to the support beams. Then, frame out the area by attaching two more 2-by-8 boards to the right and left sides. Use a drill and decking screws to do this.

Fill in the middle space with the remaining 11 joists, spaced approximately 14.25 inches apart. Use joist hangers, screws and a drill to attach them to the framework on each end.

Build the Floor with Deck Boards

Now it's time to add the 1-by-6 deck boards. Place them so that they're 1 inch tall and 6 inches wide with only enough space in between to fit a nail. This allows the wood to breathe and allows for water drainage when it rains. Use a drill and decking screws to attach the boards to the joists below.

From here, optional steps include treating the deck with exterior weatherproof stain and sealant, adding stairs depending on the height of your deck and adding a railing.


Maria Carter

Maria Carter

Maria is a seasoned writer with 10+ years in magazine publishing. She has written for House Beautiful, HGTV Gardens, Interior Design, R Home and Country Living, among other publications.