How to Build a Freestanding Deck

Updated: May 31

Decks are not always attached to a building. It's not unusual to have a deck that stands alone and is used as a place to look at the view or hide away to read a book or relax after a long day at work. You might not know how to build a freestanding deck, but it's not that much different from building a regular one. The key to building a deck that floats or stands on its own is to make sure the legs don't move around. Other than that, it's pretty simple.

What is a Freestanding Deck?

A freestanding deck is one that doesn't attach to a house wall ledger board and can stand on its own. Some decks stand on their own in an open area. This is a common way to build above-ground pool decks that stand alone.

Why Build a Freestanding Deck?

Because the house has a cantilever or a brick veneer, some decks can't be attached directly to the house with ledger boards. In other situations, like when a house is stuccoed, many builders prefer to build a freestanding deck instead of cutting and flashing stucco, which is messy and hard to do. Some older homes may not be able to support a deck addition because their walls may not be built well enough. With an extra beam and posts next to the house wall, these decks can be built to stand alone. To keep them from sinking, it's important to put these frost footings on top of compacted soil. Many new houses have backfilled soil around their foundations that hasn't settled down yet. You might have to put these footings down under the house foundation.

Read More: How to Brace a Deck from Swaying

How to Build a Freestanding or Detached Deck

Step 1: Layout & Prepare the Deck Site

First, remove weeds and debris from under the deck. If the ground is close to level, your job will be easier.

Build a box using 2 x 4s to match your deck's dimensions. Square a square or rectangular deck without math. When the box's diagonals are equal, it's square. Add 8-foot diagonal braces at each corner to keep the box square.

Place this box where the deck will be. Use 2 x 4s, bricks, or anything to level it. You can now find the footing holes your engineer or architect drew.

Spray paint the footings' outer diameter. Move the box gently so it stays square. You'll now use the box to lay anchor bolts on damp footings.

Step 2: Dig Concrete Footing Holes

Dig the right diameter holes to the needed depth as laid forth on the structural engineer's or architect's blueprints. Cut rebar before mixing concrete. It's smart to widen the hole's bottom. This spreads the deck's weight over more soil and prevents footing frost heave.

Each footing should be 4 inches above the soil or completed grade. This keeps wood or steel deck posts above puddles or overland water flow. It helps detect potential pest infestations. To make a nice-looking concrete footing, you may need to build little forms. You can buy cardboard tubes and plastic footing shapes.

Once the holes are excavated to the desired depth and loose soil is compacted, install the 2 x 4 box where the deck will be. Find footing forms here. You must know the middle of your deck's support posts. This is where you'll insert an anchor bolt in wet concrete.

Step 3: Pour the Concrete Footings

You can order concrete from a ready-mix facility or buy bagged concrete to mix yourself. Doing the calculations, bagged concrete usually makes more sense.

Read the bagged concrete directions before adding water. Overwatering weakens concrete. Mixing concrete should resemble thick applesauce.

Pour and mix concrete until it fills each hole in the shape. Smooth the protruding footing using a wood or magnesium float. Insert anchor bolts in the centre of each deck post.

Step 4: Install the Posts

Deck posts are crucial. They convey the deck's weight to the footings. No weak posts! Engineers and architects may request 6 × 6 wood posts for this purpose.

The posts are attached to the concrete footings using the anchor bolt you inserted. This hardware raises the wood post an inch off the concrete. This keeps wood posts dry.

Install the post bases on the concrete footings and brace them with stacked 2 x 4s. Each post should be horizontal and vertical. Once the posts are in place, cut or notch them to the precise height for the beam. Check the braces so the posts don't fall. The deck's two longest legs will likely contain beams. Create an L-shaped notch with a circular and reciprocating saw for these beams. If you don't want to construct an L-shaped notch, you can buy steel frame connections. Never nail beams directly to posts. Unacceptable.

Once you have the beam's height, you can compute post height. Use an optical level or laser level to level the post tops. Before trimming each post, triple-check your measurements. You have one shot.

Step 5: Build the Beam

Engineers or architects sized your beam (s). Beams and joists should be #1 grade. Stronger wood with fewer knots. Follow the plan for building the beam (s). Two pieces of lumber must be nailed or bolted together virtually often.

Copper is a preservative in modern treated lumber. Copper in water can corrode iron and steel. Use exposed-rated nails, bolts, and hardware. Simpson Strong-Tie helps you choose the optimum fasteners and structural hardware. Engineers and architects can recommend safe fasteners.

Step 6: Set the Beam

This beam will be heavy. If you want to stand on a platform that is more than 5 feet off the ground, it is best to use pipe scaffolding. Get enough help to lift and hold the beams in place while they're being fixed to the posts. Again, follow the instructions on the plan made by the engineer or architect. Don't guess how the beam should be connected to the posts. Your life and the lives of your loved ones depend on you building this freestanding deck so it won't fall down. Once the beam is in place, make sure it's level and that it's at the right height.

Step 7: Install the Floor Joists

Your layout specifies floor joist size and spacing. Use straight, minimally-crowned joists. Crown is a joist hump. All joists should be topped so the hump points skyward. Crowned joists should be cut. Chalk a line across the crown and cut it off, or trace a good joist's crown on a defective one. All joists must be flat or have nearly the same crown for smooth decking.

Installing composite decking requires following instructions. Attach a treated 2 x 4 along any joists with butt seams. Many composite decking systems require the decking ends to rest on 1.5 inches of solid wood, not 34-inch as with a butt joint on a single joist. Attach joists to beams with the right nails or screws. If necessary, drill pilot holes to avoid splitting a joist's beam base.

Step 8: Lay the Deck Boards