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Formwork Tie Calculator

Tie count, load per tie and diameter selection for wall formwork.

Quick answer

With the default inputs: Wall length 15 m · Wall height 3 m · Horizontal spacing 0.6 m etc.Number of ties 156 bars

Use your own dimensions ↓

Inputs

Result

Number of ties
156bars
Horizontal count26bars
Vertical count6bars
Load per tie18.0kN
SelectionM14 (allowable 20.3 kN)
How this is worked out

A formwork tie runs through the wall and clamps the two wales, carrying the fresh-concrete pressure; tighter spacing means less load per tie. Load per tie = horizontal × vertical spacing × pressure, and the diameter follows: M12 12.9, M14 20.3, M16 30.0, M20 47.4 kN (common Q235 allowables). Pressure is not uniform with depth - it peaks at the bottom, so tighten the lower rows. Sleeve ties in PVC tube so they pull out; those left in the wall need corrosion treatment.

Next up: Formwork Turnover Calculator · Formwork Lateral Pressure Calculator

Formula

Tie countn = (⌊L÷sh⌋+1) × (⌊H÷sv⌋+1)
Load per tieN = sh × sv × pressure
SelectionN ≤ allowable (M12 12.9 / M14 20.3 / M16 30.0 / M20 47.4 kN)
A 15 m × 3 m wall at 0.6×0.6 m, 50 kN/m²: 26×6 = 156 ties, 0.6×0.6×50 = 18 kN each, M14 (20.3 kN allowable) is enough.

How to work it out

  1. Form ties = ⌈wall length ÷ horizontal spacing⌉ × ⌈wall height ÷ vertical spacing⌉, spacing usually 0.45-0.6 m.
  2. Load per tie = horizontal × vertical spacing × fresh-concrete lateral pressure, taken at the design value.
  3. Select by allowable tension: M12 12.9 kN / M14 20.3 kN / M16 30.0 kN / M20 47.4 kN.
  4. If the load exceeds the allowance, step up a size or tighten the spacing - never push through.
  5. For waterproof walls (basement, tank), the through-sleeve takes a waterstop ring, and the holes are plugged after stripping.

Where it goes wrong

Material and cost

Form ties with through-sleeves are priced per piece, reusable or one-shot. The tiny cost of waterstops and hole-plugging is nothing against the cost of chasing leaks after the fact.

On site

Basis

FAQ

How is the pressure taken?
Fresh-concrete pressure depends on pour rate, temperature, slump and vibration, and is not simply γH. Low walls poured slowly press lightly (about 40 kN/m²); high walls, fast pours and pumping push it to 60-70 kN/m². A firm value follows a formula such as ACI 347 from height and rate; here the bands are for quick selection. Pressure is triangular with depth and peaks at the bottom, so tighten the lower rows.
Must ties be sleeved?
Yes. A PVC sleeve lets the tie be pulled and reused, saving material and removing a corrosion path. Unsleeved ties stay in the wall; cut ends need corrosion treatment or rust travels inward along the tie and forms a water path, worst on external walls. Water-retaining parts (basements, tanks) need waterstop ties with a welded steel disc.

Cite this page

Use this format in reports, method statements or coursework. The link is permanent.

Building Calculator. Formwork Tie Calculator. 2026-10-25. https://jianzhujisuan.com/en/formwork-tie

Results are estimating aids only and are not a design basis. Construction and final accounts must follow the drawings, the applicable standards and an approved method statement. Anything affecting structural safety, shoring or falsework must be checked by a suitably qualified engineer.