Strength and span
Galvanised steel laths are stiffer and stronger for their cost, which matters on wide industrial openings and doors that take knocks from vehicles. Steel gauges can be increased for wider spans or higher-risk openings.
Aluminium comes in two forms. Roll-formed foam-filled laths are light and insulating but not designed to resist determined attack; extruded aluminium laths are rigid double-wall profiles that close much of the gap with steel and suit most shopfronts.
Weight, motors and boxes
Lighter aluminium curtains need smaller motors and smaller boxes, which keeps house shutters neat and makes solar operation possible. Steel curtains are heavier, so they need bigger barrels, larger boxes and stronger motors, which affects how and where the shutter can be fitted.
Corrosion and finish
Aluminium does not rust and takes powder-coat and woodgrain finishes well, which is why it dominates domestic shutters and garage doors. Steel relies on galvanising, often with a powder-coat on top; scratches and coastal air speed up corrosion, so regular cleaning helps it last.
Within a few miles of the sea, aluminium or well-finished powder-coated steel is the sensible choice.
Cost
Like for like, roll-formed aluminium is usually the cheapest for small and medium openings, steel the best value for large industrial openings, and extruded aluminium the premium option for shopfronts where looks and strength both matter.
Quick guide
- House windows, doors and garages: foam-filled aluminium.
- Smart shopfronts and coastal sites: extruded aluminium or powder-coated steel.
- Warehouses, depots and farm buildings: galvanised steel, insulated if the building is heated.
What about security?
Neither material is secure on its own merits. Security depends on the lath profile, the guides, the locking and whether the complete product has been attack-tested. If you need a rated shutter, compare tested products rather than materials, and ask for the certificate for the exact product being quoted.
This guide is general information, not legal advice. Rules can change; check with the relevant authority for your property.