Deck Footing Size Chart
In order to determine the proper size for your footings, you will need to establish how much total weight they are going to have to support and what kind of soil they are covering. To calculate the load, you should use 40lbs per square foot for live loads (these are variable loads that are dynamic such as the weight of people and furniture) and 15 lbs per square foot for dead loads (this is the weight of the materials used for the construction of the deck) for a total load weight of 55 lbs per square foot.
For example, if you are building a 10x10 deck attached to a house with two footings on the corners, you could calculate the loads for the footings in the following way. First, draw a line dividing the deck into two halves between the house and the footings. The load for the section nearest the house will be transferred back to the ledger board and carried down to the house foundation. The remaining half of the deck will again be split into two parts to be supported by the two corner footings. This is called the tributary load. If you multiply the area of this section 5’ x 5’, you will get 25 square feet. You can multiply this area by 55 lbs per square foot loading to come up with 1,375 lbs total load. Once you know the total load, you can use the chart below to determine the footing size for your soil conditions. Always be sure to check your calculations with your local building inspections department before digging.

Circular Footings
Maximum Allowable Load Per Footing, in Lbs
Soil Type | Gravel | Sand | Clay | |
Allowable Pressure (Lbs /Sq Ft) | 3000 | 2000 | 1500 | |
Footing Size (inches) | 12 | 2300 | 1500 | 1100 |
13 | 2700 | 1800 | 1300 | |
14 | 3200 | 2100 | 1600 | |
15 | 3600 | 2400 | 1800 | |
16 | 4100 | 2700 | 2000 | |
17 | 4700 | 3100 | 2300 | |
18 | 5300 | 3500 | 2600 | |
19 | 5900 | 3900 | 2900 | |
20 | 6500 | 4300 | 3200 | |
21 | 7200 | 4800 | 3600 | |
22 | 7900 | 5200 | 3900 | |
23 | 8600 | 5700 | 4300 | |
24 | 9400 | 6200 | 4700 |
Cutting a Concrete Pad
Learn how to use a concrete saw to cut a hole in a patio slab to install a deck footing.
Protecting From Collapse
Learn how to use cardboard sonotubes and hole covers to protect your deck footing holes from caving in and flooding before pouring concrete.
Monolithic Pier
Compare the pros and cons of installing a solid concrete deck footing using a cardboard tube or engineered forms.
How to Decorate Deck Support Columns
Browse some examples of decorative deck support posts for tall decks.
How to Create Strong Post-to-Beam Connections
Learn how to create a positive structural connection for your post to beam connections. Use lag bolts, through bolts with washers, support cleats and hardware connectors.
Reinforcing Deck Rim or Band Joists
Learn a technique to strengthen your guard rails by installing a double rim joist and adding structural blocking to reduce bounce.
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Deck Footing Size Chart
In order to determine the proper size for your footings, you will need to establish how much total weight they are going to have to support and what kind of soil they are covering. To calculate the load, you should use 40lbs per square foot for live loads (these are variable loads that are dynamic such as the weight of people and furniture) and 15 lbs per square foot for dead loads (this is the weight of the materials used for the construction of the deck) for a total load weight of 55 lbs per square foot.
For example, if you are building a 10x10 deck attached to a house with two footings on the corners, you could calculate the loads for the footings in the following way. First, draw a line dividing the deck into two halves between the house and the footings. The load for the section nearest the house will be transferred back to the ledger board and carried down to the house foundation. The remaining half of the deck will again be split into two parts to be supported by the two corner footings. This is called the tributary load. If you multiply the area of this section 5’ x 5’, you will get 25 square feet. You can multiply this area by 55 lbs per square foot loading to come up with 1,375 lbs total load. Once you know the total load, you can use the chart below to determine the footing size for your soil conditions. Always be sure to check your calculations with your local building inspections department before digging.

Circular Footings
Maximum Allowable Load Per Footing, in Lbs
Soil Type | Gravel | Sand | Clay | |
Allowable Pressure (Lbs /Sq Ft) | 3000 | 2000 | 1500 | |
Footing Size (inches) | 12 | 2300 | 1500 | 1100 |
13 | 2700 | 1800 | 1300 | |
14 | 3200 | 2100 | 1600 | |
15 | 3600 | 2400 | 1800 | |
16 | 4100 | 2700 | 2000 | |
17 | 4700 | 3100 | 2300 | |
18 | 5300 | 3500 | 2600 | |
19 | 5900 | 3900 | 2900 | |
20 | 6500 | 4300 | 3200 | |
21 | 7200 | 4800 | 3600 | |
22 | 7900 | 5200 | 3900 | |
23 | 8600 | 5700 | 4300 | |
24 | 9400 | 6200 | 4700 |
Cutting a Concrete Pad
Learn how to use a concrete saw to cut a hole in a patio slab to install a deck footing.
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Sinking deck footings can lead to serious problems. Learn what can cause concrete footings to sink. Properly installed footings will resist sinking.
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Learn how to hand dig or mechanically dig your deck footings with step-by-step instructions. Learn what to do if you hit a rock.
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Browse some examples of decorative deck support posts for tall decks.
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Explore Articles by Topic

Footings
Information related to installing frost footings for decks

Framing
Learn structural framing methods

Decking
Learn about wood and composite decking materials

Stairs
An in-depth look at the complex issue of how to build stairs

Railings
How to install guardrails and handrails to meet IRC code

Features
An overview on water drainage, benches, planters and lights

Design
The basics of deck design

Planning
Learn about permits and working with contractors

Porches & Patios
Build a covered deck to enjoy all seasons

Ledger
Proper attachment techniques

Care
Maintain your deck to maintain your investment

Materials
An overview on water drainage, benches, planters and lights