Glass Roof Leak Repair for Commercial Buildings

Why glass roofs leak

A glass roof is a system, not a sheet of glass. Panes or sealed units sit on glazing bars and are held down by capping or pressure plates. Gaskets or sealant form the weather line, and gutters and flashings carry the water away at the edges. Water usually runs along a bar or across a soffit before it drips, so the stain on the floor is rarely under the defect. The causes we find most often are:

• Failed seals and gaskets. Rubber gaskets shrink, harden and pull back from the corners, and sealant joints lose their grip as the roof moves and weathers.
• Glazing bars and capping. Loose, lifted or missing capping, failed bar-end closures and blocked drainage channels inside the bars.
• Cracked or broken panes. Thermal stress, impact or a failed sealed unit lets water straight through and can quickly become a safety issue.
• Putty and lead on heritage roofs. On Victorian patent glazing, perished putty, cracked paint and lifted lead are the usual ways in.
• Gutters, flashings and abutments. Blocked valley gutters and failed upstands or flashings at walls and ridges overflow back under the glass.
• Condensation that looks like a leak. We check for it, so you do not pay to reseal a roof that is not leaking.

How we find and fix a leaking glass roof

Every job follows the same order: protect the space below, prove the entry path, make safe, then repair once. That keeps the atria, concourses, shops and offices under the roof open wherever possible.

• Close-quarters inspection. We get onto or under the roof by rope access, MEWP, tracked spider lift or internal access, photograph each bay and check the gaskets, capping, glass, gutters and flashings.
• Water testing where appropriate. If the path is not obvious, controlled water testing bay by bay isolates the joint that is letting water in. The tracing method is set out on glazing leak detection.
• Temporary make-safe. Where water is getting in or glass is cracked, we fit temporary seals, covers or boarding and set out exclusion zones below so the building can keep running.
• Permanent repair. This depends on what we find. We might reseal or regasket the affected bays, refix or renew the capping, clear and reseal the gutters and flashings, re-putty heritage panes, or replace cracked glass and failed sealed units.
• Record and handover. You get before-and-after photographs for FM, estates and insurers, plus a note of anything else we saw while we were at height.

Access without shutting the building

Most glass roofs sit over spaces that cannot close. We choose the access that disrupts least and costs the client least. That means rope access for sloped roofs, domes and lanterns, MEWPs and spider lifts for atria and canopies, and roof-top working with edge protection where the structure allows it. Scaffold is used only when it is genuinely the right answer. See glass replacement without scaffolding and rope access glazing.

Heritage glass roofs

We have carried out multiple projects over 10 years at Alexandra Palace, a Grade II listed London landmark, including external sealing to the three major glazed roofs. On the single glazed Victorian heritage glass roofs at Alexandra Palace, 194 glass panes were replaced on one roof and 112 × 7mm Georgian wired glass panes on another. Heritage roofs need care with historic bars, putty, lead and glass type. There is more on heritage glazing and the Alexandra Palace hub.

Is this the right page for your leak?

This page covers leaks through glass roofs: sloped and pitched glazing, atria, rooflights, lanterns and canopies. For leaks through curtain walling, windows or vertical glazed screens on occupied floors, see commercial glass leak repair. For the refurbishment of a whole atrium or rooflight, see atrium and rooflight glazing. If glass is broken and water is coming in now, go straight to emergency glazing make-safe or call 020 3780 3001.

What we deliver

• Close-quarters glass roof, atrium and rooflight leak inspection
• Water testing to prove the entry path where appropriate
• Temporary make-safe, covers and exclusion zones over occupied space
• Resealing, regasketing and capping renewal on affected bays
• Cracked pane and failed sealed unit replacement
• Heritage re-putty and lead work on Victorian patent glazing
• Photographic record for FM, estates and insurers

How the work is done

Roof types	Sloped and pitched glass roofs, atria, rooflights, roof lanterns, glazed canopies, heritage glass roofs
Typical causes	Seals and gaskets, glazing bars and capping, cracked panes, heritage putty, gutters and flashings
Sequence	Protect below, inspect, test where needed, make-safe, permanent repair, record
Access methods	Rope access, MEWP, tracked spider lift, internal access with protection
Working hours	Daytime, out-of-hours and agreed service windows
Coverage	London HQ, Midlands office in Radcliffe, Nottingham, UK-wide programmes

Questions we get asked