Isolated Spread Footing Design Step by Step — Full Worked Example (ACI 318-25, ASCE 7-22)
2:08Published July 8, 2026Narrated, with captions and a full transcriptAlso on YouTube
Design an isolated spread footing in StructSuite per ACI 318-25 and ASCE 7-22 — start to finish. Soil bearing, one-way (beam) shear, two-way punching shear, flexure and development length, each reported as a demand-capacity ratio next to the code section it comes from. The first footing fails on bearing at D/C 1.27, and the fix is made on screen.
Transcript and details
About this video
What you will see
- The module opens empty, with nothing pre-filled
- Step 1 Geometry: an isolated footing under a column, the support material (a wood column) and its position, interior. Position is not cosmetic, it sets alpha-s in the punching-shear equation per ACI 318-25 Section 22.6.5.3 (interior 40, edge 30, corner 20)
- A first-pass footing, 5 x 5 ft in plan and 18 in thick, then the step collapsed to its blue summary
- Step 2 Materials: f'c = 3000 psi, Grade 60 steel, and the allowable soil bearing from the geotechnical report, 3000 psf
- Reinforcement: twelve #5 bars each way on 3 in of cover, the cover ACI 318-25 Table 20.5.1.3.1 requires for concrete cast against and permanently in contact with ground
- Step 3 Load Definition: 50 kips dead and 40 kips live at the base of the column, plus the Seismic Design Category, which decides which combinations get generated
- Step 4 Design Verification, split into the two tables a footing actually needs: the geotechnical check on ASCE 7-22 ASD service combinations, and the structural design on ACI 318-25 LRFD factored combinations
- The 5 x 5 footing failing at bearing D/C 1.27, and why soil bearing is the check that sizes a footing
- Enlarging to 8 x 8 ft and watching every ratio drop below 1
- Every load combination and check listed with its exact ACI 318-25 section reference
The footing in this example
An interior wood column, 7.5 in x 7.5 in, carrying 50 kips dead and 40 kips live. First try: 5 x 5 ft, 18 in thick, service bearing D/C 1.27 against a 3000 psf allowable, so it fails. Final design: 8 x 8 ft x 18 in, f'c = 3000 psi, Grade 60, twelve #5 bars each way on 3 in cover, Seismic Design Category B. Every check passes: soil bearing per ACI 318-25 Section 13.3.1.1, one-way shear per Section 13.2.6.2(a), punching shear as the least of Table 22.6.5.2 (a), (b) and (c), flexure at the face of the support per Table 13.2.7.1 with As,min = 0.0018bh per Section 7.6.1.1, and development length by the simplified method of Table 25.4.2.3.
Codes referenced: ACI 318-25 Chapters 7, 13, 20, 21, 22 and 25; ASCE 7-22 Chapters 2 and 11.
Transcript
The narration word for word, 241 words, from the video's own captions. Select a time to play from there.
Isolated Footing — ACI 318-25
0:02In this tutorial we'll design an isolated spread footing per ACI 318-25 — checking soil bearing, one-way and punching shear, and flexural reinforcement.
Add the Footing module
0:13From the dashboard, add the Isolated and Strip Footing module. It opens empty. Step one, geometry. It's an isolated footing under a column. Choose the support material — a wood column — and its position: interior.
Enter footing size — first try 5x5 ft
0:32Enter the footing plan size — let's first try five feet by five — and its thickness, eighteen inches. Collapse the step to see its blue summary.
Step 2 — concrete, steel & bearing
0:44Step two, materials. Set the concrete strength to three thousand psi, keep Grade 60 steel, and enter the allowable soil bearing from the geotechnical report — three thousand psf.
Reinforcement — #5 bars each way
0:56Then the reinforcement: number-five bars, twelve each way, with three inches of cover.
Materials summarized
1:10Collapse it. Step three, the loads at the base of the column — fifty kips dead, forty kips live — and the Seismic Design Category, B.
Loads summarized
1:25Collapse it. Step four runs the ACI checks as demand-capacity ratios. At five-by-five the bearing ratio is one-point-two-seven — above one — so the footing fails.
Enlarge the footing to 8x8
1:37So go back to step one and enlarge the footing to eight feet by eight. Back to verification. At eight-by-eight every ratio drops below one — bearing, one-way and punching shear, flexure, and development length all pass.
Each check cites its ACI 318-25 section
1:55Every load combination and check is listed with its exact ACI 318-25 section reference. And that's a complete isolated-footing design, ready for your report.