Ask most Salt Lake City homeowners what a concrete footing is, and you’ll likely get a blank stare. Yet footings are arguably the most important concrete work on any property. They are the underground base that distributes the weight of structures — decks, additions, fences, retaining walls, and homes themselves — into the ground below. Get footings right, and your structures stand level and solid for generations. Get them wrong, and settling, cracking, and eventual structural failure follow.
What Is a Concrete Footing?
A footing is a widened concrete base placed at or below the frost line that supports a vertical load. Think of it like a snowshoe — it spreads weight over a larger area so the structure above doesn’t sink into the soil. Footings vary in size and shape depending on the load they carry: continuous strip footings under foundation walls, spread footings under columns, and pier footings under deck posts are the most common types in residential construction.
The Frost Line in Salt Lake City
This is the critical detail for Utah homeowners: footings must extend below the frost depth to prevent frost heave. When soil freezes, it expands. If a footing is above the frost line, that expansion can push the entire structure upward — sometimes unevenly, causing cracking, doors that won’t close, and structural damage. In Salt Lake City, the minimum frost depth is typically 30 inches, though it varies by elevation and location. Check with Salt Lake City Building Services for the specific requirement in your project area — footings in the Cottonwood Canyon area, for example, must go deeper than footings in lower-elevation neighborhoods.
Footing Sizes and Dimensions
Salt Lake City building codes specify minimum footing dimensions based on the load carried. For a typical residential deck, piers might be 10 to 12 inches in diameter at a depth of 30 to 36 inches. For home foundation walls, continuous footings are typically 24 inches wide and 12 inches deep (below the frost line). Always consult your local building code and pull a permit — improperly sized footings are one of the most common building code violations discovered during home inspections.
Excavation in Utah Soils
Salt Lake City sits on soils that range from sandy gravel in the foothills to soft, expansive lakebed clays near the valley floor. Clay-rich soils are particularly challenging for footings — they swell when wet and shrink when dry, creating movement that can stress footings over time. In areas with known problematic soils, a geotechnical engineer’s input may be valuable before designing footings for significant structures.
Forming and Pouring Footings
For pier footings, tubular fiber forms (Sonotubes) are the standard choice. They’re easy to cut to length, hold their shape during pouring, and peel away cleanly after curing. For continuous strip footings, trench the excavated soil itself often serves as the form, with boards added at the top to control the pour height.
Use 3,000 to 4,000 PSI concrete for footings. In Salt Lake City’s seismic zone — the Wasatch Front has significant earthquake risk — consult with a structural engineer on footing design for any significant structure. Rebar is typically required in footings for anything beyond small deck piers.
Seismic Considerations on the Wasatch Front
Salt Lake City sits along the Wasatch Fault, one of the most hazardous fault systems in the United States. This matters for footing design. Modern building codes require seismic design provisions for new construction, which may include deeper footings, more reinforcement, and specific anchor bolt patterns. If you’re building a significant structure in Salt Lake City, working with a licensed structural engineer isn’t just good practice — it may be required by the building department.
Inspections
Most Salt Lake City building permits for projects with footings require inspections at multiple stages: after excavation and form setting (before pouring), and after pouring and stripping forms. Do not pour concrete before your footing inspection is approved. An inspector who finds poured footings at the wrong depth or inadequate size can require you to break them out and start over — an expensive lesson.
Common Footing Mistakes
The most common footing mistakes in Salt Lake City residential projects are: not going deep enough below the frost line, using undersized footings for the intended load, not using reinforcement where required, and skipping permits and inspections. All of these shortcuts eventually reveal themselves through structural problems that are expensive and disruptive to fix.
Final Thoughts
Footings are invisible once a project is complete, but they determine the long-term performance of everything above them. In Salt Lake City’s challenging climate and seismic environment, properly designed and installed footings aren’t optional — they’re the foundation of structural reliability. Whether you’re adding a deck, building an addition, or replacing a retaining wall, take footings seriously. The cost of doing them right is far less than the cost of remedying a failure.