A continuous footing under a basement wall — width and thickness straight from the table

Width and thickness come straight from IRC Table R403.1(1) — no calculation. The same 3-story basement house needs a 22″ footing on 1,500 psf clay, but only the table's 12″ minimum on 4,000 psf rock.

A cross-section through a basement foundation wall showing the continuous concrete footing beneath it, wider than the wall it carries, sitting on undisturbed soil. For a 3-story house with a basement, 20 psf roof and snow load, on 1,500 psf clay soil, the footing is dimensioned 22 inches wide and 7 inches thick, read directly from IRC Table R403.1(1) rather than calculated. A comparison strip below shows the same house on 4,000 psf rock needing only a 12-inch-wide footing, the table's own minimum — illustrating that better soil bearing shrinks the required footing at the same load and story count. — Source: IRC 2021 Table R403.1(1)

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A cross-section through a basement foundation wall showing the continuous concrete footing beneath it, wider than the wall it carries, sitting on undisturbed soil. For a 3-story house with a basement, 20 psf roof and snow load, on 1,500 psf clay soil, the footing is dimensioned 22 inches wide and 7 inches thick, read directly from IRC Table R403.1(1) rather than calculated. A comparison strip below shows the same house on 4,000 psf rock needing only a 12-inch-wide footing, the table's own minimum — illustrating that better soil bearing shrinks the required footing at the same load and story count.

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<figure style="margin:0;max-width:800px">
  <a href="https://remodelcalculators.com/construction-diagrams/footing-size-cross-section" target="_blank" rel="noopener">
    <img src="https://remodelcalculators.com/api/figure-embed/footing-size-cross-section" alt="A cross-section through a basement foundation wall showing the continuous concrete footing beneath it, wider than the wall it carries, sitting on undisturbed soil. For a 3-story house with a basement, 20 psf roof and snow load, on 1,500 psf clay soil, the footing is dimensioned 22 inches wide and 7 inches thick, read directly from IRC Table R403.1(1) rather than calculated. A comparison strip below shows the same house on 4,000 psf rock needing only a 12-inch-wide footing, the table's own minimum — illustrating that better soil bearing shrinks the required footing at the same load and story count." width="800" height="600" style="width:100%;height:auto;border:0" loading="lazy">
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    Diagram: <a href="https://remodelcalculators.com/construction-diagrams/footing-size-cross-section" target="_blank" rel="noopener">A continuous footing under a basement wall — width and thickness straight from the table</a> — courtesy of <a href="https://remodelcalculators.com" target="_blank" rel="noopener">RemodelCalculators.com</a>
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