Glazing in Places of Worship

The significance of the window will rest not just in its glazing (the glass, the lead cames joining the glass pieces together, and the supporting ferramenta) but in the stone of the window surrounds. In any place of worship, it may be a single window or a single light that is important, or it may be an ensemble of several windows.

If the windows of a place of worship incorporate historic glazing, this will have a great impact on the appearance of the building not just in the interior, but as seen from the exterior during the day and at night.

We strongly encourage you to keep glazing of interest wherever possible. We advise you not to remove individual elements from larger compositions, for example figurative elements which are designed to be seen within a decorative setting. If you are re-using windows from elsewhere, we recommend that you place them in openings of closely matching dimensions.

Caring for historic glass

Windows are a critical part of the building “envelope” that separates the exterior from the interior. That means they are exposed to the weather, and must be able to stop rain and wind entering the building. Glass and metal also change temperature quickly in response to the air temperature and sunlight. This leaves them prone to condensation on the interior, especially in buildings with damp environments and/or poorly designed heating systems.

The environment can cause numerous conservation problems for historic glass, from distortion, to leaking, to corrosion of the glass and loss of painted detailing.

Other common issues include cracked or lost panes, failure of the lead cames, bowing (where the weight of the glass is no longer properly supported), and the corrosion of ferramenta damaging stone mullions.

Glazing can also be at risk from day-to-day cleaning or the use of window reveals, if these are not conducted with great care.

For more information on looking after stained glass windows, see our technical guidance.

Conserving historic glass

Your denominational body may have stained glass consultants, from whom you can seek advice.

When considering the conservation and repair of historic windows, we strongly encourage you to consult both your Inspecting Architect and specialist conservators (specialisms including glazing, ironwork, and stone). In some cases it may also be necessary to bring in building performance expertise, to better understand the causes of environmental problems such as corrosion.

Often securing the long-term future of historic glazing requires no more than minor repairs and specialist cleaning, which can also make a large difference to the look of the glass and its contribution to a space. Your conservator will be able to guide you on good principles for daily care and maintenance.

Dealing with moisture problems in the building will go a long way to reducing environmental problems such as condensation, but for fragile and important glass you may also wish to consider environmental protective glazing (EPG). An experienced and accredited glass conservator can help you and your Inspecting Architect to balance protecting the glazing with the inevitable visual and physical impact EPG will have on the building’s historic character and appearance.

For physical protection of historic glass from vandalism and other impact damage, see our advice on Security.

New stained glass

If you are adding new stained glass windows, you must first assess the significance of any existing glazing (bearing in mind that the building may be notable for a lack of stained glass), and of any fabric that would be removed or altered. You must also consider the liturgical meaning as well as the artistic merits of the new glass.

Advice and permissions

If you're making alterations to a listed building, such as installing EPG or new glazing, you may need to get permission from your local authority and/or denominational body.