A Deck Footing Calculator helps builders, contractors, and homeowners determine the number of footings required to support a deck safely and efficiently. Deck footings are essential structural components that distribute the weight of the deck, furniture, and occupants evenly to prevent sinking or instability.
By using this calculator, users can estimate the number of footings needed, calculate the load per footing, and ensure that the deck meets building code requirements for structural integrity and safety. Proper footing placement prevents deck sagging, uneven weight distribution, and potential failures over time.
Formula for Deck Footing Calculation
To determine the number of footings required, use the following formula:
Number of Footings
Number of Footings = (Deck Length / Spacing) + 1
Where:
Deck Length = Total length of the deck (feet)
Spacing = Distance between footings (feet)
+1 ensures footings are placed at both ends
Load Per Footing
To calculate the load each footing must support, use this formula:
Load per Footing = (Total Deck Load) / (Number of Footings)
Where:
Total Deck Load = (Deck Area × Load per Square Foot)
Common residential deck load: 50 lbs per square foot (psf)
This ensures that each footing is capable of handling the appropriate weight, preventing structural issues such as shifting, cracking, or sinking over time.
Deck Footing Reference Table
The following table provides estimated footing requirements for common deck sizes and spacing intervals to help users quickly determine their deck’s support needs.
| Deck Size (ft) | Footing Spacing (ft) | Number of Footings | Load per Footing (lbs) |
|---|---|---|---|
| 10 × 10 | 4 | 4 | 1250 |
| 12 × 12 | 6 | 3 | 2400 |
| 16 × 16 | 6 | 4 | 3200 |
| 20 × 12 | 5 | 5 | 2400 |
| 24 × 20 | 8 | 4 | 6000 |
This table provides a quick reference for deck builders, helping them determine the optimal footing placement for strength and safety.
Example of Deck Footing Calculator
A homeowner is building a 12 ft × 16 ft deck with footings spaced 6 feet apart.
Step 1: Calculate the Number of Footings
Number of Footings = (Deck Length / Spacing) + 1
= (16 / 6) + 1
≈ 4 footings
Step 2: Calculate the Total Deck Load
Total Deck Load = (Deck Area × Load per Square Foot)
= (12 × 16) × 50
= 9,600 lbs
Step 3: Calculate the Load Per Footing
Load per Footing = (Total Deck Load) / (Number of Footings)
= 9,600 / 4
= 2,400 lbs per footing
This means each footing must be capable of supporting 2,400 lbs to ensure the deck remains stable and structurally sound.
Most Common FAQs
Proper footing spacing evenly distributes the deck’s weight, preventing sagging, tilting, or structural failure. Incorrect spacing can lead to excessive stress on certain areas, increasing the risk of damage.
Footings should extend below the frost line to prevent heaving and shifting in colder climates. Check local building codes for recommended footing depth in your area.
Yes, larger footings with a greater load-bearing capacity can reduce the total number needed, but they must still meet weight distribution and stability requirements. Always consult with a structural engineer or local building authority.