Are flat rooflights secure?

Getting onto the roof is the first barrier

Security thinking about rooflights starts one level down. A unit on a two-storey rear roof, reached only by a ladder carried across a garden in view of neighbouring windows, is a poor target whatever it is made of.

A unit on a single-storey extension behind a fence, next to a flat garage roof, reached by standing on a bin, is a different proposition. So the first thing we look at on a survey is not the product. It is what a person would have to do to stand next to it, how visible they would be doing it, and how long they could work there undisturbed. That assessment changes the specification more than any brochure figure.

How the frame is held down to the kerb

The commonest weakness we find on existing units has nothing to do with glass. It is a frame sitting on a kerb held by a thin line of sealant and four fixings, sometimes fewer.

A unit fixed the way it should be has mechanical fixings at close centres through the frame into solid timber, typically at 300mm to 400mm intervals and always within 150mm of each corner, into a kerb that is itself screwed down into the deck and the joists below. The result cannot be levered off as a unit. Where we replace an old dome we usually find the original kerb was never fixed to anything except the felt.

Whether the glass can be lifted out of its frame

This is the question worth asking a supplier and the one people rarely ask. In an externally glazed unit the sealed pane is held in place by a bead or a capping fitted from the outside. Remove that capping and the glass lifts out, leaving an open hole and no broken glass at all.

An internally glazed unit, or one where the pane is structurally bonded to the frame with a silicone joint, cannot be dealt with that way. The bond is continuous, the pane is part of the frame, and the only route through it is breaking laminated glass, which is loud, slow and leaves the interlayer in place.

What laminated glass actually does under attack

Laminated glass is not unbreakable, and nobody should sell it that way. What it does is stay in one piece. A struck pane crazes across its face but the plastic interlayer holds the fragments together, so the opening does not clear and the intruder has to keep working at it, noisily, to cut a hole big enough to climb through.

Toughened glass behaves in the opposite way. It resists a first blow well and then goes all at once into a heap of small pieces, leaving a clear opening in a second. That is why the outer pane may be toughened for thermal reasons but the inner pane should be laminated. Our flat rooflight security and laminated glass page goes into the interlayer thicknesses in detail.

Domes, polycarbonate and what they resist

A multi-wall polycarbonate dome behaves differently again. It does not shatter, which sounds like an advantage, but it can be cut with a knife along a rib and folded back, quietly, in under a minute. Older acrylic domes become brittle with ultraviolet exposure and crack under a boot.

This matters most because domes are what sit on the roofs that are easiest to reach: garages, utility rooms, single-storey side returns. If a dome on a low roof is being replaced anyway, replacing it with a glazed unit rather than another dome is the single largest security improvement available on that roof, and it usually costs less than people expect once the kerb is already there.

Opening units, actuators and locking

A fixed pane has no moving parts and nothing to force. An opening unit introduces a mechanism, and the question is what holds it shut.

An electrically operated unit driven by a chain or spindle actuator is self-locking under load: the gearing cannot be back-driven, so pushing on the sash does not open it. Manual units vary. A pole-operated rooflight with a single central catch is weaker than one with multi-point locking engaging along two edges. On any unit reachable from a low roof we specify either an electric actuator or multi-point locking, and we make sure the actuator is fed through the ceiling rather than through the frame face where the cable can be cut.

New dwellings and the standard that applies

Where a rooflight is easily accessible in a newly created dwelling, including a converted outbuilding or an annexe, security requirements under Part Q of the Building Regulations apply, and easily accessible has a definition based on how the unit can be reached rather than on storey height alone.

That normally means glazing and hardware tested to a recognised security standard, and the manufacturer supplying evidence of it. For an extension to an existing house the requirement does not bite, but the same specification is available and is worth taking on a low roof. Building Control notification for the work is handled by us as part of the job.

Alarms, sensors and planning the cable

If a rooflight is going onto an alarmed house, decide before installation rather than afterwards. A contact on an opening unit needs a cable run to the frame, and running it after the ceiling is closed means lifting the reveal.

Glass-break detectors are a poor fit for laminated panes because the pane may never break cleanly enough to trigger them. A movement detector covering the room below the unit is more reliable and does not depend on the glazing at all. We are happy to leave a draw cord into the kerb for an alarm engineer to use later, at no real cost, if it is asked for while the roof is open.

Being straight about what a rooflight will not do

No rooflight is a safe. Anybody prepared to work at height with tools, in daylight, in view, can get through any glazed unit eventually. What good specification buys is time and noise, and both of those are what actually deters an opportunist.

The honest position is this. On a first-floor or second-storey roof, spend your money on glass performance and forget security. On a garage, a single-storey side return or anything reachable from a boundary wall, spend it on laminated inner glass, bonded glazing and a properly fixed kerb. Our rooflights on a garage roof page covers those roofs specifically. We work across Oxford and up to twenty five miles by road, and our workmanship carries a ten-year guarantee.