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Calcs.com
United States
IBC 2024IBC 2021ACI 318-14

Pole Footing (IBC 2024)

US structural engineers embedding pier, pole, and deck-post footings to the current IBC 2024 code, where lateral loads and uplift govern the embedment depth. Post axial and lateral reactions link from the connected column or deck-beam calculation above, so embedment, bearing, and uplift checks update automatically when loads change.

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What it calculates

Post and column loads link directly from the calculations above, so changes propagate to the footing automatically. Design pier, pole, and deck-post footings to ACI 318-19 per IBC 2024. Results cover lateral embedment, vertical bearing, compression-bending interaction, shear, and uplift with skin friction resistance below the active soil zone.

Code standards

  • IBC 2024
  • ACI 318-19
  • ASCE 7-22

How it calculates

The Pole Footing (IBC 2024) calculator designs plain (unreinforced) concrete pier, pole, and deck-post footings to ACI 318-19 under IBC 2024, with ASD and LRFD load combinations from ASCE 7-22 (Ch. 2). The pier is assumed to be continuously restrained against buckling by the surrounding soil, so unbraced-length effects are neglected in the concrete compression checks.

Lateral embedment (IBC 2024, Cl. 1807.3)

The governing check for pole footings is the embedment depth needed to resist lateral load without excessive rotation. The IBC 2024 method evaluates the lateral soil-bearing pressure at one-third of the embedment depth and at the full depth:

  • S_(1/3) - lateral soil stress at one-third of the embedment depth
  • S_d - lateral soil stress at the full embedment depth

utilization = S_d / S_allow ≤ 1.0

For nonconstrained posts (free to rotate at grade) the required embedment is solved from moment equilibrium; a constrained post (braced at grade) permits a shorter depth.

Vertical bearing

Gross vertical bearing pressure is the total downward service load divided by the pier base area:

utilization = q_gross / q_a ≤ 1.0

Compression and bending capacity (ACI 318-19, Ch. 21)

The pier is checked as a plain concrete member under combined axial load and moment. Nominal moment capacity is evaluated on the tension and compression faces and combined with the compression capacity:

utilization = (P_u / (phi × P_n)) + (M_u / (phi × M_n)) ≤ 1.0

with phi = 0.60 for plain concrete in combined loading.

Shear capacity (ACI 318-19, Ch. 21)

One-way shear demand is compared to the plain-concrete shear strength:

utilization = V_u / (phi × V_c) ≤ 1.0

Uplift and downward safety factors

Uplift from wind or seismic is resisted by self-weight plus skin friction below the active soil movement zone:

FS_uplift = (W_pier + W_soil + f_s × A_skin) / T_net ≥ FS_min

A downward capacity check confirms the pier and bearing soil carry the maximum compressive service load:

FS_down = R_down / P_max ≥ FS_min

The active (movement) zone depth is a user input, so skin friction acts only below it. The wall or post self-weight above is not counted in the uplift resistance.

Concrete bearing at the post interface (ACI 318-19, Cl. 22.8)

Bearing stress where the post or bracket lands on the pier is compared to the plain-concrete bearing capacity. This check governs when concentrated loads transfer from a steel post base or bracket into the top of the pier.

Assumptions

The post is centred on a prismatic pier and designed separately. The footing is unreinforced (plain) concrete. Per IBC 2024 Cl. 1807.3, embedded posts are not used to provide lateral support for materials such as plaster, masonry, or concrete unless separate bracing is provided. Pier deflection and movement, where applicable, are checked separately.

Related calculators

Pier Footing (IBC 2021)→Pier Footing (ACI 318-14)→Combined Footing→Spread Footing (IBC 2024)→

What engineers say

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Just the simple feature of being able to link loads is a really big time-saver.

Sam Hensler

Principal, Dynamic Analysis Engineering Consulting

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The load linking feature is huge for us. Before, we had to use separate calculators and manually input everything.

John Cagle

Project Engineer, CHM Engineering

Frequently asked questions

What design standards does this calculator use?
The calculator uses IBC 2024 Cl. 1807.3 for lateral embedment, ACI 318-19 Chapter 21 for plain-concrete compression, bending, shear, and bearing capacity, and ASCE 7-22 (Ch. 2) for ASD and LRFD load combinations. This is the current edition for 2024 IBC projects.
What are the key inputs?
Key inputs are pier diameter, embedment depth, and height above ground, concrete strength and density, the post type and dimensions (round or rectangular post, or steel bracket bearing width and length), allowable gross soil bearing capacity, allowable lateral soil pressure per unit depth, allowable uplift and downward skin friction values, length of the active (movement) soil zone, and the height at which lateral load is applied. Applied vertical and lateral loads can be entered manually or linked from a post or column calculation above.
What does the calculator check and output?
It checks lateral embedment (the required versus provided depth), vertical bearing pressure, combined compression and bending capacity of the plain-concrete pier, one-way shear, concrete bearing at the post interface, and uplift and downward safety factors including skin friction below the active soil zone. Demand, capacity, and utilization are reported for each check.
Can I use it for deck posts, poles, and bracket-mounted columns?
Yes. The calculator suits residential and light-commercial pier, pole, and deck-post footings. Choose a round or rectangular embedded post, or a steel post landing on a bracket, and enter the base reaction (often from a deck-beam calculation above). Concentric loads set the lateral load to zero; lateral wind or seismic loads drive the embedment check.
How is the embedment depth determined, and what does the active soil zone do?
Embedment follows IBC 2024 Cl. 1807.3, comparing the lateral soil-bearing pressure at one-third of the depth and at full depth against the allowable. Nonconstrained posts (free at grade) need a deeper embedment solved from moment equilibrium; a constrained post (braced at grade) can be shorter. The active (movement) zone depth is a separate input, and uplift skin friction is credited only below it - relevant on expansive or frost-susceptible soils.
Does this calculator support load linking with column or post calculations?
Yes. If a column, post, or deck-beam calculation sits above the footing in the same Calcs.com project, the axial and lateral reactions at the base link directly. When the loading or member above changes, the footing automatically re-runs embedment, bearing, compression-bending, shear, and uplift with the updated reactions - no manual re-entry.

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