How To Build Deck Footings?

How To Build Deck Footings: A Comprehensive Step-by-Step Guide

A dream deck provides the perfect outdoor entertaining space and a beautiful backyard addition. But without strong, stable footings supporting it below the surface, your deck could easily become a nightmare. Settling, shifting, sagging – all unwelcome threats if footings are improperly sized, positioned or constructed.

Let’s delve into the critical steps for planning and building watertight footings that will securely support your deck for decades to come. With the right footing design, diligent layout, proper preparation and quality construction, you can have full confidence in your deck’s foundation.



Why Proper Deck Footings Are Essential

Deck footings provide the base of your deck foundation system. Their key purpose is to transfer the weight of the entire deck structure and any live loads (people, furniture, etc.) into the ground below.

Without footings, the 4×4 or 6×6 support posts bearing all the deck load would sink right into the soil. The tiny surface area of a typical post base cannot diffuse the high pounds per square inch (psi) safely. Footings enlarge this concentrated load’s contact area significantly so the ground can support the deck without destabilizing.

Footings must also extend below the frost line depth to avoid shifting from seasonal ground freezing and thawing. And they are typically made of poured concrete reinforced as needed with rebar or other steel elements.

The local building code specifies exact footing sizing, thickness, depth, reinforcement requirements and more based on your deck’s permitted structural design. There is no shortcutting proper footings – but construct them right and your deck will stand strong.


Deck Footing: Types, Size, Layout

Let’s look at some of the key footing considerations:

  • Concrete slab– Rectangular pad, typically 2×2 ft up to 3×3 ft. Simplest option for lighter decks.
  • Tube– Cylindrical concrete pier with straight sides. Relies on soil friction. Best for clay-heavy soils.
  • Bell– Flared, bell-shaped to distribute weight on larger base. Good for heavier loads.
  • Column and pier– Separate footings and piers. Advanced DIY option.
  • 2 feet square by 8 inches thick is typical minimum for simple designs.
  • Poor soil conditions or heavy deck loads require larger footings of 3 x 3 feet or more.
  • Exact size is specified on permitted plans based on total deck load calculations.
  • Footing layout must precisely match structural design.
  • Spacing between footings is dictated by joist span lengths. Often 4 feet to 8 feet on center.
  • Perimeter ledger boards and staircases also require footings to support attachments.
  • Have certified deck plans before you calculate and mark any layout.

deck footing


Install Deck Footings

Step1: Prepare the Site for Safe Footing Excavation

With the footing locations mapped out on your approved plans, it’s time to prepare the site. Safety first!

Step2: Underground Utilities
  • Contact your local utilities via 110 or online to identify and mark any buried electric, gas, sewer or other lines on site. Failure to do this can result in extremely dangerous (and costly) mishaps.
  • Check for any private utility lines you may have installed for landscape lighting, external buildings etc.
Step3: Clear Away Debris
  • Remove all vegetation, organic matter and other debris from footing locations.
  • Level and tamp down the soil surface to a compacted, even grade.
Step4: Precise Layout
  • Carefully measure and mark out the exact footing hole centers based on your plans. Verify dimensions.
  • Double check the alignment between corresponding holes for a post and its beam support footing. They must line up perfectly.
Step5: Test Holes
  • In key locations, dig a few test holes about 3 feet down to identify any unexpected bedrock or high water table issues before excavating all holes.
Step6: Proper Drainage Slope
  • The ground around the home’s foundation should always slope away from the house to prevent water pooling. Verify footing locations accommodate this.
Step7: How to Dig Proper Footing Holes

Now comes the fun part – digging all the footing holes. Do it right with these tips:

Round Point Shovel: A round point shovel will cut into the soil cleanly while minimizing disturbances to the hole sides and bottom. Maintain straight edges and a flat bottom.

Power Auger: For large deck projects, renting an auger can bore perfect holes with ease in all but the most challenging soils. Much simpler than using manual post hole diggers.

Busting Through Roots and Rocks: Excavating tools like reciprocating saws, hammer drills with spade bits or pick axes efficiently cut through unavoidable large roots or rocks obstructing holes.

Loose Soil: Before pouring concrete, tamp and compact any loose soil at the hole bottom to prevent future settling. Use a hand tamper or 6×6 post pounded up and down.

Frost Line Depth: Footing holes must extend below the frost line depth for your region, plus 2 to 3 extra inches for a safety margin. Don’t risk frost upheaval! Verify required depth.

Step8: Mix and pour concrete bases   

Once your hole is properly dug to the correct depth and diameter, mix the concrete and begin pouring the legs:

Mix concrete: Thoroughly mix the dry concrete with water according to the manufacturer’s instructions. The ideal consistency is loose and roughly “applesauce”. Not too wet and runny.

Pour concrete: Carefully pour the concrete into the holes in the base. Use the wand to find hidden openings and fill holes if necessary.

 Disable Level: When all holes are filled, level the excess concrete flush with the surrounding soil or level.

 Format top: Use a concrete auger to profile and slope the top surface to drain rainwater. The “dome” shape works well.

Anchor bolts: Place the required anchor bolts in the wet concrete in precisely marked locations according to your approved deck plans until it still needs work.

Hardening Phase: Allow the concrete to fully cure for at least 5 days before building the deck columns and structure on the base. Moist curing is best.

Step9: Improved sole models   

Here are some more tips for more complex feet:

Steel reinforcement:If necessary, before pouring the concrete, carefully place a steel bar or other reinforcement according to the structural model in the holes of the base.

Overview: If required by local building code, check foundation holes and steel reinforcement before pouring concrete.

Pipe molds: If you are using round pipe feet, press the concrete forms into the holes before pouring to get smooth and straight sides.

Two-Step Casting: First pour the lower concrete base for the column and platform legs. Then pour the pillar pier after the subbase has hardened.

Strong Walls: In cold climates, detached deck legs can be placed on frozen walls that extend below the frost line and provide stable support.


Deck Plinth Basic Maintenance

With oversight on material specifications and quality construction following your approved plans, the footings for your new deck should serve reliably for decades. But here are some tips for ongoing footing care:

  • Periodically inspect concrete footings and frost walls for any developing cracks or signs of shifting. Immediately address any issues.
  • Ensure good drainage under the deck. Keep soil sloped away from footings and no vegetation or debris buildup on concrete. Standing water undermines foundation.
  • Avoid excessive deck bounce or vibration from high-impact activities like jumping. Can gradually loosen footings over time.
  • Annually check anchor bolts and post base connections to concrete footings. Verify all still secure. Tighten hardware as needed.


Invest time designing proper footings, carefully lay out locations, dig holes to accurate depth, use high quality concrete and materials, and your deck will be supported by an incredibly sturdy foundation. Don’t cut corners – the footing stage sets the tone for your deck’s longevity and safety. Build it right from the start.

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