The Best Footing Type for a Deck

Design Objectives of Deck Footings

• There are six design objectives for the footing of a wooden deck: Structural integrity, elevation above ground level, separation from soil and water contact, length of serviceability, drainage and airflow. Of equal concern -- though not design-affecting -- is the required satisfaction of all local building codes, inspections and approvals. Other factors that impact footing design are cost, construction time, deck type and local weather. In the final analysis, the footing design that should be used is the one that best performs under the specific conditions of soil, weather, deck type and load-bearing requirements.

Primary Deck Footing Types

• The primary footing types for residential deck are as follows:

  1. Post attached to concrete pier: this most popular footing type involves sinking concrete piers below frost level and embedding a "J"-bolt into the soft concrete. The deck support posts are attached to the concrete piers by 5-sided galvanized-steel post anchors.

  2. Direct beam attachment to concrete footings: this footing design alternative connects the posts directly to existing concrete footings or imbedded concrete blocks. Its primary advantages are speed of construction and cost but it has a limited length of serviceability and it rarely satisfies local building codes.

  3. Direct beam attachment to a concrete patio: this footing design alternative attaches the posts to an existing concrete structure -- typically a patio -- that was built prior to deck design. Its only positive design characteristic is cost. Most building codes do not allow this footing type for decks that are anchored to an existing above-ground structure.

  4. Concrete slabs over patterned concrete, brick or stone: this footing design alternative provides limited footing capability, as posts rest unattached to brick or stone that has been overlaid with paivers. This design has limited application, typically in warm climates, and is rarely approved for use in cold or wet climates.

  5. Free-floating posts on imbedded blocks: this alternative is listed as a footing but is not permanently attached to posts or superstructure. Its only advantages are cost and time of construction. This footing type is most often utilized in the support of free-floating garden decks.

Other Factors Affecting Footing Design

• The factors of cost and construction time are intertwined and often overshadow more critical design considerations. Certainly the simpler and less involved the design, the quicker its construction time and the lower its cost. The deck type is often a significant issue because building codes have typically evolved to satisfy different types of decks. Decks that are structure-attached are singled out as requiring the most structural support and the soundest mooring to the earth. Finally, weather is a prime governing factor, especially in wet or cold regions.

The Best Footing Type for a Deck

• The single best footing for a deck is the "post attached to concrete pier" type. This footing design type scores first in all design objectives. Its greatly superior advantages easily outweigh the considerations of cost and construction time. The American Wood Council lists only two advisable deck footing types in its literature. Those are the "post attached to concrete pier" and "direct beam attachment to concrete footings", clearly favoring the former, the one most favored by builders and accepted by building codes nationwide.