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Concrete Formwork Tie Spacing Calculator

Compute the maximum square-grid spacing for form ties, given the fresh concrete's lateral pressure and the tie's rated capacity.

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

Maximum tie spacing

1.47 ft

Check your inputs

This assumes a uniform square grid and uniform pressure across the form face — real formwork design must also check the sheathing and stud/waler capacity between ties, not just the tie spacing alone.

Allowable tie load (after safety factor)
10 kN
Tributary area per tie
2.15 ft²

For the dimensions entered, expect a maximum tie spacing of 0.45 m (square grid). Moderate confidence — sound arithmetic, but allow for the variation any real site introduces. Set for United States against IRC 2024. The market selector changes both the units and the code cited.

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

  • Each form tie's tributary area = its allowable (safety-factored) load capacity / the fresh concrete lateral pressure; assuming a square grid, spacing = sqrt(tributary area)

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Frequently asked questions

Why is the spacing a square root of area?
Assuming ties are arranged on a uniform square grid, each tie supports a square patch of formwork (its tributary area) — the spacing between ties is simply the side length of that square.
Does this account for pressure varying with height?
No — it uses one design pressure value for the whole form face. Real formwork often varies tie spacing vertically, using tighter spacing near the base where pressure is highest and wider spacing near the top.
What if my ties aren't in a square grid?
For a rectangular grid, pick a horizontal spacing and divide the tributary area by it to get the vertical spacing (or vice versa) — the tributary area result stays valid regardless of the grid's aspect ratio.