Structural expansion joint — vertical GS MW S/CH panel layout

Junction function

Building structural expansion joint = a structural break in the steel/reinforced concrete frame required for buildings longer than ~60–80 m (PN-EN 1992 / PN-EN 1993). It allows free thermal movement between two parts of the building — without an expansion joint, the structure cracks under the strain of cold/warm steel expansion.

In a sandwich panel façade, a structural expansion joint MUST be reflected in the cladding — otherwise the sandwich panels crack at the joints under ±10–20 mm structural movement.

Solution:

1. Custom expansion flashing (item 03) = flexible bent element of “Z” or “Omega” type; absorbs ±20 mm of horizontal movement.
2. OB-17 cover flashing (item 04) conceals the moving flashing from the interior side.
3. On-site insulation (item 05) — mineral wool in a 100–200 mm wide strip; not bonded, loosely inserted so it can flex with the joint.

Critical installation aspects

• Expansion flashing (item 03) — designed individually based on the structural movement amplitude (from the structural engineer’s calculations); typical range ±15–25 mm.
• Fixing of the expansion flashing — only to one side of the joint (never to both at once!); typically to the “fixed” side of the structure, with the movable side sliding relative to the flashing.
• Insulation in the joint strip (item 05) with class A1 mineral wool — not polyurethane foam (foam cracks under the movement amplitude); mineral wool remains flexible.
• Zone around the joint free of rigid fasteners — within a 50 cm strip from the joint, do not anchor the panel to the movable structure; adjacent panels are fixed only to their “fixed” side.
• Inspection after the first winter/summer — visually + with thermal imaging; the expansion flashing should show trace microcracks (a sign that it is working) or look as new (fixed too rigidly?).
• Halls longer than 100 m — require at least 2 expansion joints located at 1/3 and 2/3 of the length; verify with the structural calculations.

Occurs in long-span halls (industrial, logistics, warehouse).

Documentation

Technical Catalogue GS MW S/CH/U (Gór-Stal 2025), page 20 — Structural expansion joint, vertical layout. Scale 1:5.

Components in this junction