Calculate footings and concrete needed
Deck footings provide the foundation that supports your entire deck structure. Proper footing design prevents settling, shifting, and structural failure.
Key Components:
• Footings: Concrete piers below frost line
• Posts: Vertical supports (4x4 or 6x6)
• Beams: Horizontal supports on posts
• Joists: Smaller beams supporting decking
| Climate Zone | Frost Depth | Minimum Footing Depth |
|---|---|---|
| Southern States | 0-12" | 18" below grade |
| Mid-Atlantic | 24-36" | 42" below grade |
| Northern States | 48-60" | 66" below grade |
Frost Heave: Water in soil freezes, expands, and lifts footings. Footings must extend 6" below frost line to prevent movement.
Post Spacing Guidelines:
• 4-6 feet: Heavy loads, large spans, hot tubs
• 6-8 feet: Standard residential decks
• Maximum 8 feet: Never exceed without engineer
approval
Footing Size Selection:
• 8" diameter: Small, low decks (under 2' high)
• 10" diameter: Standard residential decks
• 12" diameter: Large decks, 2nd story
• 16" diameter: Heavy loads, poor soil
Load Calculations:
• Dead load: 10 PSF (deck structure weight)
• Live load: 40-50 PSF (people, furniture)
• Hot tub: 100 PSF (water weight + people)
• Snow load: Varies by region (add 20-50 PSF)
Code Requirements:
• Footings must reach below frost line
• Minimum 6" below frost depth
• Posts must be anchored to footings
• Ledger board must be properly flashed
• Check local building codes (vary by region)
Concrete Tips:
• Use 3000 PSI concrete minimum
• One 80-lb bag = 0.6 cubic feet
• Add 10% waste for spillage
• Mix bags or order ready-mix for 1+ yards
• Set post brackets while concrete is wet
How to use: Enter deck dimensions, select post spacing and frost depth for your area. Calculator determines number of footings, hole dimensions, and concrete needed. Always check local building codes before starting.