Zinc Dome of 127-year-old Mosque Receives Repairs, Waterproof Coating

The Shah Jahan Mosque is listed as a building of special interest under the National Heritage.

The Shah Jahan Mosque is listed as a building of special interest under the National Heritage.

The upkeep of buildings of high regard is a rewarding opportunity for Belzona. This was true of the application presented by the Shah Jahan Mosque in Woking, UK. Built in 1889 by Dr. Gottleib Leitner outside of Muslim Spain, it has stood for a staggering 127 years. Possessing historical and religious associations, this building warranted efforts to preserve its condition. Therefore, the mosque has the honor of being listed as a building of special interest under the National Heritage, attaining historical Grade II status. Meanwhile, registering as an independent charity means that, since 1995, the local community has invested in renovation and restoration of the mosque.

The Problem

Included as a homage to the green-colored dome at the Prophet’s Mosque in Medina, the design has become a part of Shah Jahan Mosque’s heritage. However, over the course of its lifetime, the zinc dome had become damaged and was showing signs of aging. It was suffering from a number of perforations around its circumference, as well as holes, due to weathering and corrosion of the metal. In addition, the design comprised of a lateral band formed by 41 zinc stars, which had similarly succumbed to corrosion and loss of shape. All of this damage led to rainwater leaking into the mosque, causing disruption to the prayer times and community events taking place.

The zinc dome was suffering from a number of perforations and holes around its circumference due to weathering and corrosion of the metal.

The zinc dome was suffering from a number of perforations and holes around its circumference due to weathering and corrosion of the metal.


In search of a solution, the mosque made inquiries with companies who utilized traditional hot work repair methods, all of whom rejected the application in fear of aggravating the problems further. Due to the thin- and through-wall defects in the already fragile zinc dome, it was believed to be impossible to weld repairs without causing additional damage. As a result, a cold-applied alternative was recommended to both rebuild the existing metalwork, as well as provide a waterproof coating for future protection.

The Application

Prior to application acceptance, Belzona carried out a series of pull-off tests on the dome’s current coating to assess its adhesion strength. Once the adhesion levels were determined, it was understood that the existing coating could be sufficiently removed using hand tools, creating a surface profile void of deteriorated coating and corrosion. The dome, measuring a total of 6.5 meters in diameter, was examined to identify and repair any thin- and through-wall defects. Starting with the most damaged areas, the application to rebuild and resurface the dome’s profile was carried out using Belzona 1121 (Super XL-Metal). Incorporated with a fine steel mesh over the large perforations in the zinc structure, the metal repair composite was cold-applied without the need for specialist tools.

To fully restore the dome, the Belzona membrane was painted green with a compatible coating system.

To fully restore the dome, the Belzona membrane was painted green with a compatible coating system.


Following some additional sanding, Belzona had restored a surface onto which the waterproof membrane could be laid. Once more, the substrate was cleaned and prepared in line with Belzona protocol, before the conditioner was applied across the entire dome and the seamless system of Belzona 3111 (Flexible Membrane) was installed. The liquid-applied membrane demonstrated its ability to conform to the various contours of the dome, providing the mosque with roof protection.

Altogether, two applicators took a total of three days to complete the repairs and protection of the mosque roof. In order to fully restore the dome, the Belzona membrane was painted green with a compatible coating system. Left uncoated, the stars and crescent moon were subsequently gilded by the client, in line with the dome’s original design. Content with the repairs, the specialist works manager commented on behalf of the Shah Jahan Mosque, saying: “The works carried out look incredible. Thank you from both myself and our client at the Mosque.”

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