> ## Documentation Index
> Fetch the complete documentation index at: https://calcs.com/docs/llms.txt
> Use this file to discover all available pages before exploring further.

# How to Design a Spread Footing to ACI 318-14

> How to Design a Spread Footing to ACI 318-14

Learn how to design a simple residential concrete spread footing in Calcs.com, including specifying soil properties, load, footing size, and reinforcement.

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## Sliding check: what the calculator models

The **Spread Footing calculator** (ACI 318-14, ACI 318-19, and IBC 2024 versions) computes sliding resistance using **base friction only**:

**Sliding resistance = μ × (P + W\_f)**

where **μ** is the lateral sliding coefficient between concrete and soil, **P** is the ASD axial load, and **W\_f** is the factored footing and soil self-weight. The sliding demand vs. resistance breakdown is shown when the results section is expanded.

<Warning>
  **Passive earth pressure is not modeled** as a resistance term. There are no inputs for a passive pressure coefficient, embedment depth for passive resistance, or soil shear strength, and it is not listed in the assumptions.
</Warning>

If passive pressure is a significant contributor to sliding resistance for your design, you'll need to evaluate it separately outside the calculator and combine it manually with the calculator's friction resistance.