How to Build a Floating Deck？
A floating deck is a freestanding outdoor platform that sits on the ground without being attached to the house. It rests on concrete deck blocks instead of buried footings, which eliminates deep excavation and simplifies construction. A floating deck can be placed anywhere in the yard and moved or repositioned later if needed.
Two people can build a 10 x 12 ft floating deck in one weekend. Total material cost ranges from $500 to $1,400, depending on whether you choose pressure-treated lumber or composite decking. Hiring a contractor costs $20 to $60 per sq ft, or $2,400 to $7,200 for a 120 sq ft deck.
This guide covers everything from site preparation through finished decking for a standard 10 x 12 ft (120 sq ft) floating deck.
Table of Contents
What You Need: Tools and Materials
Tools
Circular saw, or miter saw, drill/driver with impact setting, 4 ft or 6 ft level, tape measure, speed square, chalk line, rake, hand tamper, string line, safety glasses, and hearing protection.
Materials for a 10 x 12 ft Floating Deck
| Item | Quantity | Estimated Cost |
| Concrete deck blocks | 9 (3 x 3 grid) | $63 to $90 ($7 to $10 each) |
| Pressure treated 2×8 joists (12 ft) | 6 boards, spaced 16 inches on center | $90 to $120 |
| Pressure treated 2×8 rim joists (10 ft) | 2 boards | $30 to $40 |
| Decking boards (12 ft composite or 5/4 x 6 lumber) | 20 boards | $240 to $700 |
| Joist hangers | 6 hangers | $24 |
| Deck screws (2.5 inch exterior rated) or hidden fastener clips | 5 lb box or 1 kit | $25 to $60 |
| Crushed gravel (3/4 inch) | 0.5 cubic yards | $25 to $35 |
| Landscape fabric (4 x 50 ft roll) | 1 roll | $15 to $20 |
| Joist tape (optional, extends joist lifespan) | 1 roll | $15 to $25 |
| Total (pressure treated decking) | $530 to $800 | |
| Total (composite decking) | $900 to $1,400 |
Surface Material Options
| Material | Cost per sq ft | Maintenance | Lifespan | Best For |
| Pressure treated lumber | $3 to $7 | Stain every 2 to 3 years | 15 to 20 years | Budget builds |
| Cedar | $5 to $10 | Oil annually | 15 to 25 years | Natural appearance |
| Capped composite | $6 to $12 | Wash only, no staining | 25 to 30 years | Low maintenance |
EVODEK capped composite decking uses a co-extruded polymer shell that resists moisture, UV fading, and stains without sealing. For a floating deck close to ground level, choose composite boards with solid profiles and capped construction for maximum moisture resistance.
Step-by-Step Instructions
Step 1: Check Local Codes and Call 811
In many U.S. jurisdictions, freestanding decks under 30 inches above grade and under 200 sq ft do not require a building permit. Rules vary by locality. Always check with your local building department before starting.
Step 2: Prepare the Site
Mark the deck footprint (10 x 12 ft) with string lines and stakes. Use the 3, 4, 5 method to confirm the corners are square: measure 3 ft along one side, 4 ft along the adjacent side, and check that the diagonal between those two points is exactly 5 ft. If it is, the corner is square.
Remove 2 to 4 inches of topsoil within the marked area. Lay landscape fabric over the exposed soil to suppress weed growth. Spread 2 to 4 inches of 3/4 inch crushed gravel over the fabric. Compact the gravel with a hand tamper to create a firm, level base. Grade the surface with a slight slope (1/4 inch per foot) away from any nearby structure for drainage.
Skipping the gravel base is the most common DIY mistake. Deck blocks placed directly on soil settle unevenly as the ground absorbs water and freezes.
Step 3: Place Deck Blocks
Arrange 9 concrete deck blocks in a 3 x 3 grid. Space the blocks approximately 5 ft apart in both directions. The outer rows support the rim joists. The middle row supports the interior joists at midspan, preventing sag. Each block should sit firmly on the compacted gravel with its top surface level. Deck blocks cost $7 to $10 each and are available at most home improvement stores.
Use a long, straight board and a level to check that all 9 blocks sit at the same height. Adjust individual blocks by adding or removing gravel beneath them. Work from the highest corner to the lowest. Accurate leveling at this stage saves significant time during framing because an unlevel foundation creates problems that compound with every subsequent step.
Step 4: Build the Frame
Cut two pressure-treated 2×8 boards to 12 ft for the long rim joists and two to 10 ft for the short rim joists. Assemble the rectangular outer frame by attaching the short boards between the ends of the long boards using 3-inch exterior screws.
Check that the frame is square by measuring diagonally from corner to corner. Both diagonals should be equal. If they differ, push the longer diagonal corner inward until the measurements match.
Set the completed frame on the deck blocks. The long sides rest on the three blocks in each outer row. Confirm the frame is level in both directions. Adjust block height as needed.
Step 5: Install Joists
Cut the remaining 2×8 boards to fit inside the frame as joists. Space the joists 16 inches on center (measure from the center of one joist to the center of the next). Attach each joist to the rim joists using joist hangers and the specified fasteners.
Optional: Apply joist tape to the top surface of all joists before installing decking. Joist tape creates a moisture barrier between the joists and decking boards, reducing rot and extending the frame’s lifespan by several years.
Step 6: Install Decking Boards
Start from the most visible edge and work outward. Overhang the decking 1 to 1.5 inches past the rim joist on the sides.
For pressure-treated lumber: leave a 1/8 inch gap between boards for drainage. Pre-drill near board ends to prevent splitting. Use 2.5-inch exterior-rated deck screws, two per joist.
For composite decking: follow the manufacturer’s expansion gap specifications. EVODEK boards require approximately 3/16 inch end to end gap and 5 to 8 mm side-to-side gap. Use the manufacturer’s hidden fastener system for a clean surface with no visible screws.
After all boards are installed, snap a chalk line along the overhanging ends and cut a straight line with a circular saw for a clean edge.
Step 7: Finish and Protect
Attach fascia boards to the rim joists to cover the exposed frame and create a finished appearance.
For wood decking, apply a weather-resistant stain or sealer to the entire surface and let it dry completely before use. Restain every 2 to 3 years. For composite decking, no staining or sealing is required. Wash with soap and water twice per year to keep the surface clean.
Conclusion
A floating deck is one of the most accessible DIY outdoor projects. A 10 x 12 ft deck takes one weekend for two people using the materials listed above. The key steps are proper ground preparation, correct block placement, level framing, and appropriate board gap sizing for your chosen material.
Composite decking eliminates ongoing staining and sealing costs while lasting 25 to 30 years. Inspect the gravel base and landscape fabric annually to confirm drainage and weed control remain effective. Sweep the deck surface weekly and wash with soap and water twice per year.
Order free EVODEK samples to compare colors and textures, or use the decking calculator to estimate material quantities for your project.
FAQ
How much does a floating deck cost?
A DIY 10 x 12 ft (120 sq ft) floating deck costs $500 to $800 with pressure-treated lumber or $900 to $1,400 with composite decking. Hiring a contractor costs $20 to $60 per sq ft, or $2,400 to $7,200 for a 120 sq ft deck. The decking boards account for roughly half of the total materials budget.
Do you need a permit for a floating deck?
In many jurisdictions, freestanding decks under 30 inches above grade and under 200 sq ft do not require a permit. However, rules vary by locality, and some homeowner associations have additional restrictions. Always check with your local building department before starting construction.
How long does it take to build a floating deck?
Two people can build a 10 x 12 ft floating deck in one weekend: Saturday for site preparation and framing, Sunday for decking and finishing. Working alone adds roughly half a day. Having all materials and tools on site before starting prevents delays.
Can you build a floating deck with composite decking?
Yes. Composite decking works well on floating decks. Use capped composite boards with solid profiles for maximum moisture resistance near ground level. Follow the manufacturer’s gap specifications for thermal expansion. Composite requires no staining or sealing, reducing long-term maintenance to periodic soap and water cleaning.
How long does a floating deck last?
A floating deck built with pressure-treated lumber lasts 15 to 20 years with regular staining. A floating deck built with capped composite decking lasts 25 to 30 years with minimal maintenance. The gravel base and landscape fabric should be inspected annually to confirm that drainage and weed control remain effective.
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