Why Proper Deck Footings Matter

Incorrect footing size or depth is a leading cause of deck failures. Footings must extend below the frost line to prevent heaving during freeze-thaw cycles, and their diameter must be adequate to support the deck's load on your specific soil type.

Calculation Guide

Measure your deck's planned width and length
Research your local building code for frost depth requirements
Determine your soil type through a simple test (ribbon test for clay content)
Space footings at 6-8 foot intervals along the deck perimeter and beams

Reference Table: Soil Bearing Capacity

Soil Type	Bearing Capacity (psf)
Clay	2,000
Sand	3,000
Silt	1,500
Gravel	4,000

Important Tips

Always check with local building authorities for specific requirements
When in doubt, go deeper with footings - extra depth rarely hurts
For sloping sites, footings must be stepped to follow the grade
Use cardboard sonotube forms for clean, consistent footing holes

Frequently Asked Questions

How far below frost line should footings be?

Footings should extend at least 12 inches below the frost line to prevent frost heave. In areas with severe frost, local codes may require more.

Can deck footings be above ground?

No, deck footings must always be placed below ground level, extending below the frost line to ensure stability and prevent movement.

How many footings do I need for my deck?

The number depends on deck size and layout. Generally, place footings at each corner and every 6-8 feet along beams and ledger board.

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