You Need 1 Deck Block per Post (4-12+ for Most Decks)

Deck blocks (precast footings) support each post of a freestanding deck. A small deck (8'x10') typically needs 4-6 blocks, while larger decks (16'x20') require 12-16+. Calculate by counting posts: 1 block per post, spaced 6-8 feet apart. Always check local building codes for load requirements.

How to Calculate Deck Blocks Needed

1. Sketch your deck layout: Draw the frame, marking corner, rim, and interior posts.
2. Count all posts: Include:
   • Corners (4 for a rectangle, more for complex shapes).
   • Rim joist posts (every 6-8 feet).
   • Interior posts (for beams or large spans).
3. Add 10% extra: Account for uneven terrain or adjustments.

Deck Size Examples & Block Estimates

Key Factors Affecting Block Count

• Post spacing: Closer spacing (e.g., 6' vs. 8') = more blocks.
• Deck height: Taller decks (>3' off ground) may need extra bracing.
• Load requirements:
  • Hot tubs/spas: Double blocks or larger footings.
  • Heavy furniture: Reduce post spacing to 4-6'.
• Soil type: Soft or uneven ground may require wider block distribution.

Common Mistakes to Avoid

1. Underestimating posts: Forgetting mid-span or beam supports leads to sagging.
2. Ignoring weight distribution: Concentrated loads (e.g., grills) need extra blocks.
3. Skipping leveling: Uneven blocks cause deck instability-use a laser level.
4. Using wrong block size: Standard blocks support 1,500-3,000 lbs; verify for your deck's total weight.

Alternatives to Deck Blocks