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Expansion Joint Spacing Calculator

Work out expansion joint spacing instantly with clear inputs, formula shown and shareable results.

About Expansion Joint Spacing Calculator

Thermal movement per metre is the coefficient of expansion times the temperature range, and for concrete at 12 microstrain per degree over a 30 degree range that is 0.36 mm per metre. Dividing the joint's movement capacity by that rate gives the maximum spacing, and the number of joints is one fewer than the number of bays.

Formulas

Movement

mm per metre = coefficient x 10^-6 x temperature range x 1000

Spacing

Maximum spacing = joint movement capacity / movement per metre

Worked example

With the default values below, Expansion Joint Spacing Calculator returns Maximum joint spacing of 55.56. Change any input above and every figure here is recalculated in your browser.

Inputs used

Structure lengthminimum 0.1 m
60 m
Temperature rangeminimum 1 °C
30 °C
Coefficient of thermal expansionminimum 1 µstrain/°C
12 µstrain/°C
Movement capacity per jointminimum 1 mm
20 mm

Results

Maximum joint spacing
55.56 m
Joints required
1
Movement per metre
0.3600 mm/m
Total unrestrained movement
21.60 mm

Step by step

  1. 1Values used
  2. 2Movement
  3. 3Spacing
  4. 4Maximum joint spacing= 55.56 m
  5. 5Joints required= 1
  6. 6Movement per metre= 0.3600 mm/m
  7. 7Total unrestrained movement= 21.60 mm

Assumptions and limits

  • The result is derived only from the 4 inputs listed above. Anything not among them is not part of the calculation.
  • In particular, this calculator does not take inflation, tax, fees or charges or compounding frequency into account.
  • Figures are rounded for display to 4 decimal places, so totals built from several rounded parts can differ slightly from the unrounded arithmetic.
  • Preliminary estimate only. Movement joint layout must be designed by a qualified engineer accounting for shrinkage, creep, restraint and cladding compatibility.

How these calculators are built and tested is described on the Methodology page. If a figure looks wrong, please report it.

Preliminary estimate only. Movement joint layout must be designed by a qualified engineer accounting for shrinkage, creep, restraint and cladding compatibility.

Frequently Asked Questions

How is the Expansion Joint Spacing figure worked out?

mm per metre = coefficient x 10^-6 x temperature range x 1000. Thermal movement per metre is the coefficient of expansion times the temperature range, and for concrete at 12 microstrain per degree over a 30 degree range that is 0.36 mm per metre.

Does shrinkage need adding?

For concrete, yes. Early-age drying shrinkage can exceed thermal movement and is the reason construction joints are specified far closer than thermal calculation alone suggests.

What values do I need to enter?

This calculator takes 4 inputs: Structure length, Temperature range, Coefficient of thermal expansion, Movement capacity per joint. The pre-filled defaults are a realistic worked example — replace them with your own site or project figures.

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