Deck Post Footing Size Calculator

Footing Size Formula:

\[ Size = \frac{Load}{Bearing\ Capacity} \]

Footing Size (sq ft):

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1. What is Deck Post Footing Size Calculation?

Deck post footing size calculation determines the appropriate foundation area needed to support a deck's structural load based on the soil's bearing capacity. Proper sizing ensures deck stability and prevents settling or structural failure.

2. How Does the Calculator Work?

The calculator uses the simple formula:

\[ Size = \frac{Load}{Bearing\ Capacity} \]

Where:

\( Load \) — Total weight the footing must support (pounds)
\( Bearing\ Capacity \) — Soil's ability to support weight (pounds per square foot)
\( Size \) — Required footing area (square feet)

Explanation: This formula ensures the soil pressure does not exceed the soil's capacity to support the load.

3. Importance of Proper Footing Sizing

Details: Correct footing sizing is critical for deck safety, preventing settling, ensuring structural integrity, and meeting building code requirements. Undersized footings can lead to deck collapse or damage.

4. Using the Calculator

Tips: Enter the total load in pounds and the soil bearing capacity in pounds per square foot (psf). Typical soil bearing capacities range from 1,500-4,000 psf depending on soil type.

5. Frequently Asked Questions (FAQ)

Q1: How do I determine the total load on my deck post?
A: The total load includes the dead load (weight of structure itself) and live load (people, furniture, snow). Consult building codes for specific requirements in your area.

Q2: What are typical soil bearing capacities?
A: Soft clay: 1,000-2,000 psf; Sandy soil: 2,000-3,000 psf; Compact gravel: 3,000-4,000 psf; Bedrock: 4,000+ psf.

Q3: Should I add a safety factor to the calculation?
A: Yes, most building codes require a safety factor of 1.5-2.0. Multiply your calculated size by this factor for the final design.

Q4: How deep should deck footings be?
A: Footings should extend below the frost line in your region to prevent frost heave, typically 12-48 inches deep depending on climate.

Q5: Do I need professional help for deck footing design?
A: For small decks, this calculator may suffice, but for larger structures or uncertain soil conditions, consult a structural engineer or local building department.