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Method sheet

Thermal Movement & Metal Compatibility

Expansion and contraction from the installation temperature to the metal surface extremes; movement at the ends for the chosen anchor; qualitative dissimilar-metal screening.

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Method

thermal-expansion 1.1

Engine

1.1.0

Output status

Preliminary - review required

Review

Awaiting review

Formulas

  • dL = alpha x L x dT, each side of the installation temperature
  • Centre anchor: each end moves half

Conventions

  • Temperatures are metal surface temperatures, not air.

Limits - what it will not do

  • No joint spacing or clip design is derived.
  • Compatibility is screening, affected by moisture, exposure and coatings.

Who must review it

  • Building-envelope consultant: design metal temperatures and joint practice
  • AFS: confirm alloys and coefficients it buys

Worked example

Inputs Galvanized, 40 ft, 20 to 120 degF installed at 70 degF

Expected 0.312 in total (Fabral TB702 worked example)

Checked by an automated test on every change.

Sources

  • Technical Bulletin TB702 - Sheet Expansion - Fabral (metal roofing manufacturer), read 2026-10-16

    Coefficients of linear expansion for roofing sheet: galvanized or Galvalume steel 0.0000065 /degF; formula dL = 12 x dT x L x E.

  • C11000 Electrolytic Tough Pitch Copper - physical properties - Copper Development Association, read 2026-10-16

    Density 0.322 lb/in3 at 68 degF; coefficient of thermal expansion 9.4e-6 /degF (68-212 degF).

  • 304/304L Stainless Steel Data Sheet - Rolled Alloys, read 2026-10-16

    Density 0.285 lb/in3; mean coefficient of thermal expansion 9.2e-6 /degF (70-212 degF).

  • 3003 Aluminium datasheet - Smiths Metal Centres, read 2026-10-16

    Density 2730 kg/m3; coefficient of thermal expansion 23.2 um/m/degC.

  • VMZINC attributes (technical support - basic principles) - VMZINC, read 2026-10-16

    Density 7.18 t/m3; linear expansion 0.022 mm/m/degC parallel to the rolling direction (value differs across the roll).

  • Dissimilar Metal Corrosion in Roofing Installations - Metal Construction Association, read 2026-10-16

    Copper performs well with lead or stainless steel, not other metals; runoff from a more noble metal onto a less noble one causes corrosion without contact; separation methods.

  • Drexel Metals ES-1 installation guides - the isolation note printed on every guide - Drexel Metals, read 2026-10-16

    Isolate all metal parts from ACQ-treated wood, or any other galvanically incompatible material, with an appropriate membrane.

  • AFS Division 07 technical notes - Sealant compatibility with sheet metals - Architectural Flashing Supply, read 2026-10-16

    Acetoxy-cure silicone is not compatible with copper or lead-coated copper (the acetic acid released during cure corrodes them); polyurethane and neutral-cure silicone are broadly compatible with common architectural sheet metals. Confirm with the sealant manufacturer.