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Footing Size Formula:
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Deck footing size calculation determines the required area of concrete footings needed to properly support a deck structure based on the total load and soil bearing capacity.
The calculator uses the simple formula:
Where:
Explanation: This formula ensures that the pressure exerted on the soil does not exceed its bearing capacity, preventing settlement or structural failure.
Details: Properly sized footings are essential for deck safety and longevity. Undersized footings can lead to settling, tilting, or collapse, while oversized footings increase construction costs unnecessarily.
Tips: Enter the total load in pounds and the soil bearing capacity in pounds per square foot. Both values must be positive numbers. Consult local building codes for specific requirements in your area.
Q1: How do I determine the total load on my deck?
A: The total load includes dead load (weight of the structure itself) and live load (people, furniture, snow). Typical residential deck live load is 40-60 psf.
Q2: What is typical soil bearing capacity?
A: Soil capacity varies widely: 1500-3000 psf for clay, 2000-4000 psf for sandy soil, and 3000-6000 psf for gravel. A soil test is recommended for accurate values.
Q3: How deep should deck footings be?
A: Footings should extend below the frost line to prevent frost heave. Depth requirements vary by climate region.
Q4: Are there building code requirements for deck footings?
A: Yes, most jurisdictions have specific requirements for deck construction. Always check local building codes before construction.
Q5: Should I add a safety factor to my calculations?
A: Most building codes require a safety factor of 1.5-2.0. Multiply your calculated size by this factor for the final design.