Two Ratings, Two Different Threats

Buyers usually ask one question about a roller shutter: "Is it strong?" Strength is not one property. A security shutter has to resist two unrelated loads, and they are tested under different standards with different pass criteria.

• Intrusion resistance — how long the curtain and its guides hold against a person with tools. Measured under EN 1627 and expressed as an RC class (Resistance Class). This is the security number.
• Wind and impact resistance — how much pressure the closed curtain takes before it deflects out of its guides, and whether it survives a windborne projectile. In Australia this is covered by AS4174 and the related cyclone provisions; in Europe by the wind load classes in EN 13659 / EN 13501 context and the manufacturer's stated pressure rating.

A shutter can pass one and fail the other. A light aluminium curtain with a good lock may reach RC2 but deform out of its guides in a storm. A heavy extruded curtain built for cyclone regions may be structurally superb while its end locks are the weak point under attack. When you specify aluminum glass shutter windows for a project, you need both numbers, and you need to know which threat your site actually faces.

Reading the EN 1627 RC Classes

EN 1627 defines six resistance classes, each representing a level of attacker and a minimum resistance time. The classes that matter for residential and light commercial shutter windows are RC2 and RC3.

The critical point often missed: the RC class applies to the whole installed assembly, not to the curtain alone. EN 1627 testing evaluates the curtain, the guides, the end locks, the box, and the fixings into the substrate. A shutter curtain certified to RC3 loses that rating if it is fixed into a lightweight reveal with inadequate anchors, or if the guides are not anchored at the required spacing. This is why the factory should quote the class for the assembly as installed, and why the fixing schedule is part of the specification.

Wind and Impact Class: The Rating That Protects the Glass Behind

In cyclone and severe-storm regions the shutter's first job is not security — it is to keep windborne debris from reaching the glazing. Once a window pane is breached, internal pressurisation can lift the roof. AS4174 and the associated cyclone provisions address this with a pressure rating and, where required, an impact test.

Practical consequence for specification: the shutter's wind rating should be at least equal to the design wind pressure of the window behind it. If the window is specified for 2.5 kPa and the shutter is rated for 1.5 kPa, the shutter will fail first and expose the glazing — defeating the purpose of installing it.

Curtain Construction: What Actually Determines Both Ratings

Slat type and wall thickness

Roll-formed aluminium slats with a foam or resin core are lighter and cheaper; extruded aluminium slats are heavier, stiffer and markedly better under both attack and pressure. Wall thickness in roll-formed slats typically runs 0.8 to 1.2 mm, while extruded security slats are substantially thicker. For RC3 and for cyclone duty, extruded slats are the normal answer. Ask which type is quoted — the price difference is not arbitrary.

Guides and end retention

The guides are where the curtain is held under load and where an attacker inserts a lever. Deep guide engagement, stainless guides in coastal locations (SUS304 minimum, SUS316 preferred), and anchorage into solid substrate at the manufacturer's spacing all matter more than slat thickness alone. A thick curtain in a shallow guide is a weak assembly.

End locks and bottom rail

Roller shutters are most often defeated at the bottom rail, by levering the curtain up out of the guides. End locks that engage the guides or the box at multiple points, a bottom rail that cannot be lifted without releasing the locks, and an anti-lift device are the features that convert a weather curtain into a security curtain.

Box, spindle and drive

The box protects the rolled curtain and houses the spindle and drive. For security applications the box should not be openable from outside without tools, and the drive — manual spring, chain, or tubular motor — must be rated for the curtain weight with margin. Motorised systems need a stated duty cycle and a manual override so the shutter can still be closed during a power failure.

How the Shutter Interacts With the Window It Protects

A shutter is only as good as the opening it closes, and the two must be specified together.

The last row is a compliance point that is easy to overlook and expensive to retrofit. In most jurisdictions a bedroom or habitable-room window that serves as an emergency escape route cannot be permanently obstructed. Where shutters are required for security on those openings, they must be operable from inside, or the opening must not be relied upon for egress.

Standards Reference

Seven Questions to Ask the Factory

1. Is the RC class quoted for the curtain, or for the complete assembly including guides, box and fixings? Ask for the test report number.
2. What is the stated design wind pressure for the closed curtain, and does the curtain stay engaged in the guides at that pressure?
3. Are slats roll-formed or extruded, and what is the wall thickness?
4. What is the guide engagement depth, and what is the fixing spacing into the substrate?
5. Are the end locks multi-point, and is there an anti-lift device at the bottom rail?
6. Is the drive rated for the curtain weight with margin, and is there a manual override?
7. For openings serving as escape routes, how is internal operability achieved without compromising the RC class?

Manufacturing and Verification Chain

2026 Indicative FOB Prices for Shutter Window Systems

Prices are indicative 2026 factory FOB ranges for project volumes, excluding freight and installation. Final quotation depends on slat type and thickness, RC class with test documentation, wind and impact rating, guide and box specification, drive type (SIEGENIA, ROTO, HOPO hardware where applicable), finish, and the window package behind the shutter. Contact Rogenilan Windows Doors for a specification-matched quote.

Shutter Window FAQ

Does a heavier slat automatically mean a higher RC class?

No. The RC class is awarded to the installed assembly, and the test usually finds the weak point somewhere other than the curtain — most often at the bottom rail, the guide engagement, or the fixings into the substrate. A thick extruded curtain with a single-point end lock and shallow guides can underperform a well-detailed lighter system. Ask for the class with the test report, and ask which configuration was tested.

Can the shutter and the window have different ratings?

They can, and that is the problem. If the shutter's wind rating is lower than the window's design wind pressure, the shutter fails first and exposes the glazing. Specify both against the same site wind load, and specify the glazing — usually laminated — for the duty the shutter cannot fully cover.

Are motorised shutters a security risk if the power fails?

Only if the drive lacks a manual override or the override is accessible from outside. A motorised shutter must still be closable during a power failure, and the override must not provide an attack point. State the drive's duty cycle and torque margin against the curtain weight, since an undersized motor is the most common cause of a shutter that stops short of fully closed.

What maintenance does a security shutter need?

Guide and slat cleaning to keep the curtain running freely, lubrication at the intervals the manufacturer states, inspection of end locks and the anti-lift device, and a check that guide fixings have not worked loose. In coastal locations the stainless guides and fasteners should be inspected for contamination and surface corrosion, since chloride build-up can attack even SUS316 if it is not cleaned.

Do shutters affect the window's thermal and condensation performance?

They can help and hurt. A closed shutter adds a still-air layer that reduces heat loss and solar gain. But the box and guides penetrate the facade, and if the box bridges from outside to inside without a thermal break it becomes a condensation path. Specify a continuous PA66-GF25 break in the window frame and a box detail that does not create a cold bridge.