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Secant / Contiguous Pile Wall Overlap Calculator

Check whether a bored pile wall's spacing produces true secant overlap or a contiguous gap between piles.

Computed in your browser — nothing you enter is uploaded. Figures are presented for United States against IRC 2024, and every formula is cited under regulatory standards below.

Last verified 2026-08-26 · v1.0.0

Market
Imperial · sales tax
1.97 ft
Schematic, drawn to the proportions you entered — not to scale on screen.

Pile overlap (or gap)

0.49 ft overlap

High confidence

True secant configuration — adjacent piles physically overlap, forming a continuous water-resistant wall (assuming the secondary piles are cut into the primary piles as designed).

Spacing-to-diameter ratio
0.75

Running these inputs gives 0.15 m overlap as the pile overlap (or gap). Currently reading for United States under IRC 2024 — pick a different market above and the figures re-cast accordingly.

Estimated cost — your price

This site holds no price list for this material — local prices vary too much to publish honestly. Enter your supplier's price and the result is costed with it.

Preliminary estimate, not certified engineering. This tool produces an indicative quantity calculation for planning purposes only — it is not a certified structural analysis, a guaranteed material takeoff, or a substitute for building department approval. Always verify measurements on-site and have a licensed contractor or structural engineer review any load-bearing, code-sensitive, or safety-critical work before purchasing materials or starting construction. Spotted an arithmetic or standards error? Report it to contact@craftquantities.com with your inputs — confirmed fixes become pinned regression tests.

[Schema Verified] Computed in alignment with American Concrete Institute (ACI 318-19) formulas and International Residential Code (IRC 2024) spatial boundaries.

Regulatory standards & verification citations

  • Secant pile geometry: adjacent piles overlap when center-to-center spacing is less than the pile diameter; overlap distance = diameter minus spacing (a negative result indicates a gap, i.e. a contiguous rather than secant wall)

Your workspace

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Frequently asked questions

What's the difference between secant and contiguous pile walls?
Secant piles physically overlap (primary and secondary piles interlock), forming a continuous barrier suitable for groundwater control; contiguous piles are spaced with a small gap between them and rely on the gap being small enough (or otherwise treated) to retain soil, but don't seal against water.
What overlap amount is typically targeted?
A common target is 100-150mm (4-6 in) of overlap for secant walls, though this varies by project specification and equipment tolerance — always check your project's structural design.
Does this account for pile verticality tolerance?
No — this is a nominal geometric check based on design spacing. Real drilled piles have some verticality tolerance over depth, so deeper walls typically need more design overlap margin to guarantee actual overlap is maintained at the base.