How to Build Concrete Deck Footings

Footings are the silent backbone of every sturdy deck. If you cut corners here, the entire structure will eventually heave, sag, or settle, leading to costly repairs and structural instability later on. A solid footing transfers the weight of the deck directly to the load-bearing soil, ensuring your platform stays level regardless of the seasons. Building them right is less about speed and more about precision. You need to account for local frost depth, ensure the concrete is properly cured, and keep the post bases elevated slightly above grade to prevent rot. When finished, you should have a rock-solid foundation that keeps your deck perfectly square and safe for decades.

1. Dig Below the Frost Line. Use string lines to mark the exact perimeter of your deck. Dig your post holes to the depth required by your local building code, ensuring they extend below the frost line.
2. Compact the Gravel Base. Pour six inches of compacted gravel into the bottom of each hole. This creates a drainage layer that prevents water from pooling beneath the concrete.
3. Plumb and Align Forms. Insert concrete form tubes into the holes and ensure they are plumb. Trim the tops of the forms so they sit exactly at the same finished height.
4. Fill and Tamp Tubes. Mix your concrete in a wheelbarrow or mixer until it reaches a thick, uniform consistency. Fill the tubes, tapping the sides as you go to release trapped air bubbles.
5. Set Post Base Anchors. Immediately press your galvanized post-base anchors into the wet concrete. Use a level to ensure they are centered and perfectly vertical.
6. Wait and Backfill. Allow the concrete to cure for at least 48 hours before attaching any posts. Once fully set, backfill the remaining space around the tubes with soil.