Choosing a FootingPad Size
FootingPad Sizing Chart
The chart below provides some fundamental information about the various FootingPad sizes and what should be used based on the maximum load. Below the chart is more detailed information to guide sizing decisions.
| DIAMETER | THICKNESS | WEIGHT | MAX LOAD* | MIN. POST | COMMON USES |
|---|---|---|---|---|---|
| 10" | 1" | 1 lb. | 1,622 lbs. | 3.5" x 3.5" | Decks, Pole Barns |
| 12" | 1.5" | 2.1 lbs. | 2,356 lbs. | 3.5" x 3.5" | Decks, Pole Barns |
| 16" | 1.5" | 4 lbs. | 4,200 lbs. | 4.5" x 5.5" | Decks, Pole Barns |
| 20" | 2.5" | 9 lbs. | 6,545 lbs. | 4.5" x 5.5" | Pole Barns |
| 24" | 2.5" | 13 lbs. | 9,327 lbs. | 4.5" x 5.5" | Pole Barns |
A Simple Sizing Formula
To determine the size of the footing, a simple formula is used:
Structural Load (lbs) / Soil Capacity (psf) = Footing Surface Area Required (sq. ft.)
Here is a simple deck example:
1. Area of the deck carried by a single post/footing: 42 sq. ft. x 50* lbs./sq. ft. = 2,100 lbs.
2. Soil carrying capacity = 3,000 psf
3. Footing surface area needed: 2,100 lbs./3,000 psf = 0.7 sq. ft.
* 50 lbs / square foot of deck surface area is the standard rule of thumb to calculate deck loads. Visit https://footingpad.com/decks-footing-size-calculation-guide/ for more detailed information.
For our example, we need a footing surface area of at least 0.7 sq. ft. A 12-inch diameter or larger footing will work.
Standard footing sizes have the
following surface areas
10” diameter: 0.546 Sq feet
12” diameter: 0.786 Sq feet
16”: diameter: 1.398 Sq feet
20” diameter: 2.185 Sq feet
24” diameter: 3.146 Sq feet
Deck and Post-Frame Load Calculation Guides
Use these guides if you’d like to manually calculate your footing size by post. These guides also offer information on formulas associated with deck and post-frame building construction, including snow load weight.