Skylights, Dormers & Glazed Atria

This element covers every opening in a roof that lets in light, and the structures built up from the roof plane to do it: in-plane translucent sheets in profiled roofs, framed and domed skylights on kerbs, roof windows, patent glazing, glazed atrium roofs, lanterns, and dormers.

Overhead glass must hold together when broken. Codes require laminated glass, or toughened glass with a protective screen, in sloped and overhead glazing. Older atria often have wired glass or monolithic toughened glass that would not meet that requirement now.

Era and use shape what to expect. Warehouses and factories from the 1960s onward carry in-plane fibreglass and later polycarbonate sheets, often in regular runs across the roof, and many of them sit in asbestos cement roofs of the same era. Schools and commercial flat roofs carry domed acrylic or polycarbonate skylights on timber or metal kerbs. Shopping centres of the 1980s and 1990s carry large atrium and mall roofs of patent glazing or curtain wall sections. Victorian and Edwardian buildings carry lanterns and patent glazing with lead or putty seals.

What shortens life:

• UV: polycarbonate and fibreglass yellow, craze and become brittle.
• Hail and impact.
• Poor kerb and flashing details.
• Condensation on cold frames and glass.
• Debris on atrium roofs blocking gutters.

Fragility and fall-through

Translucent roof sheets and skylights cannot take a person's weight, and polycarbonate becomes more brittle as it ages. Falls through fragile roofs and roof lights are a leading cause of deaths in roof work in all three jurisdictions. An unprotected roof light on any roof that people walk on is a hazard regardless of condition.

UV embrittlement

Polycarbonate and fibreglass yellow, haze and lose strength; fibreglass loses its surface and exposes fibres. Light transmission falls.

Kerb and flashing leaks

Kerbs that are too low, flashings that are lapped the wrong way, and sealant-only details leak. In-plane sheets leak at laps with the adjacent metal where profiles do not match or fixings fail.

Seal and gasket failure in atria

Atrium glazing leaks at gaskets, pressure plates and glazing bar joints, often at the bottom of slopes where water collects.

Overhead glass failure

Monolithic toughened glass in overhead positions can break spontaneously and fall. Wired glass cracks from rusting wire and thermal stress. Laminated glass stays in place.

Dormer failure

Dormer cheeks, sills and flashings leak; timber decays; dormers added in conversions can lack adequate support from the roof structure.

Condensation

Single-glazed skylights and uninsulated aluminium frames are the coldest surfaces in the roof. In humid spaces (pools, kitchens, bathrooms, crowded malls) condensation forms on them, runs down and drips, and is often mistaken for a leak. Thermally broken frames and insulated glazing reduce it.

Atrium structure

Atrium roofs are carried on steel or aluminium frames that are themselves exposed to water from failed seals and condensation. Corrosion at gutters and bearings, and movement of the supporting structure, load the glazing and open joints.

From aerial imagery

• Number and layout of roof lights; discoloured, yellowed or patched sheets.
• Roof lights without mesh, covers or guardrails on roofs with plant or walkways.
• Debris and staining on atrium roofs.

On the roof

• Yellowing, crazing and brittle surfaces; cracks at fixings.
• Kerb height and flashing condition; sealant-only details.
• Gasket shrinkage and pressure plate condition on atrium glazing.
• Glass type markings on overhead glass.

Inside the building

• Leak staining around skylights and along atrium glazing bars.
• Condensation drips from frames.
• Cracked or broken overhead panes.

In the records

• Product data and non-fragility certificates.
• Glass schedule for atria; replacement records.
• Leak logs.
• Fall protection installation records.

Fracture patterns in overhead glass follow the same reading as in vertical glazing: a pair of small fragments at a point of origin inside toughened glass points to a nickel sulphide inclusion; a single crack meeting the edge at right angles points to thermal stress; cracks radiating from a point point to impact. In wired glass, cracks starting at the edge with rust staining mean the wire has corroded where the edge was not sealed.

Findings are graded by what they demand: safety (can hurt someone now), failure (failed and damaging the building), condition (distress present and progressing), lifecycle (renewal due on age and exposure), deadline (a regulator or ordinance sets the date), check (investigate before sizing works) and nil (cosmetic or stable).

A roofing surveyor inspects from safe access; a façade engineer inspects atrium glazing.

• Inventory of every roof light with type, size, condition and protection.
• Fragility assessment from product data.
• Glass identification in atria and overhead glazing.
• Water testing of kerbs and glazing joints.
• Structural inspection of atrium framing.

The report should give a roof light inventory with type, fragility, protection and condition; atrium glass types and any non-laminated overhead glass; leak paths found by testing; and the protection needed before anyone next works on the roof.

• Light transmission and discolouration readings where daylight performance matters.
• Atrium structure inspection of steel, gutters and bearings from access equipment.
• Incident review: falls and near misses on the roof.

Every roof light is recorded, not a sample, because one unprotected fragile sheet is enough to cause a fall.

• Protection: safety mesh under sheets, covers or guardrails around skylights, walkways that avoid them.
• Replacement with non-fragile rated products.
• Kerb rebuild with proper flashings.
• Atrium reglazing with laminated glass and new seals.
• Dormer repair: new flashings, cheeks and support.

Interactions: roof light replacement on industrial roofs is usually done with the roof covering, and with asbestos cement roofs it is part of the licensed removal; atrium reglazing needs protection and closures below; protection works are often the cheapest and most urgent part of any roof light scope.

• Kerb upstands raised to current heights with new flashings.
• Interim covers and exclusion zones where replacement is delayed.

Replacement is priced per unit or by area; protection per unit or by length of guardrail. Access dominates. Atrium reglazing is a lump-sum project with protection to the floor below.

Fall protection is code compliance; replacement is lifecycle; repairs are repairs and maintenance.

Safety mesh, covers and guardrails are inexpensive per roof light and should not wait for replacement. Atrium reglazing needs protection decks or scaffolds over occupied floors and out-of-hours work, which often exceed the cost of the glass. Industrial roof lights are usually replaced in the same contract as the roof covering, with licensed asbestos removal where the surrounding sheeting contains it.

• Australia. AS 4285 covers skylights; AS 1288 overhead glazing; the work health and safety regulations and the Safe Work Australia code of practice on falls require fragile surfaces to be protected.
• United Kingdom. The Work at Height Regulations 2005 require fragile surfaces to be identified and protected; the Advisory Committee for Roofsafety publishes the standard test for non-fragility (ACR[M]001); BS 5516 covers sloped glazing.
• United States. International Building Code Section 2405 covers sloped glazing and skylights; OSHA 29 CFR 1910.28 and 1926.501 require skylights to be protected by covers, guardrails or screens.

In Britain, the Construction (Design and Management) Regulations 2015 require fragile surfaces to be identified to anyone working on the roof. In strata and leasehold buildings in all three jurisdictions, roof lights over individual dwellings may belong to the dwelling while the roof is common property, which decides who pays.

• Product data and non-fragility certificates.
• Glass schedules for atria.
• Leak logs.
• Fall protection installation and inspection records.

• Records of any falls or near misses on the roof.
• Hazardous materials register for adjacent roof sheeting.
• Atrium maintenance and cleaning records.

• Asbestos register for surrounding roof sheeting.
• Atrium structural inspection records.