CASE STUDY: Heritage Leaded Light Windows for a Listed Property
As part of an all-encompassing programme of sympathetic restoration and renovation spanning over 30 years, the current custodians of a 17th Century, Grade II listed West Yorkshire farmhouse were committed to addressing their properties problematic windows.
Softwood frames and float glass had been introduced into the stone mullioned windows during the 1980’s by the property’s previous owner. These replaced earlier 20th century timber-framed windows which had in turn replaced the original leaded glazing. Historically/architecturally incorrect from the outset, ill-fitting, visually unappealing, light reducing by a third, and failing due to widespread rot, the decision was taken to seek approval to carry out a complete programme of replacement.
The Importance of Historical Research
Armed with extensive research into traditional glazing of the period and having carefully considered all potential options for replacement (including modern thermally sealed units), the owners were firmly set on the re-introduction of authentic, hand-crafted leaded lights. Following on from initial correspondence and conversations between the client and contractor, an approach was agreed in principle, estimates were submitted and several examples of similar projects were put forward and visited (the importance of which cannot be over-stated). After several years of searching, Lightworks services as a leaded light and heritage glazing specialist were formally engaged.
Discussions followed in which all the finer details of the project were agreed upon. These included key factors such as choice of materials, glazing pattern, lead size and profile along with quantity and specification of opening casements and installation methodology. Special consideration was given to the type of glass to be used within the new proposed glazing. Based on their knowledge and experience, the contractor advised the client on the suitability of several “true” cylinder glass products commercially available from producers in France (St. Just), Germany (Lamberts) and Poland (Tatra). Cylinder glass is hand-crafted by a process of mouth-blowing large “cylinders” which are then cut, kiln heated and opened out to form flat sheets. This highly skilled and technically challenging process creates an historically and architecturally authentic material recognisable by its uneven or wobbly surface reflection. Clear sheets and pale tints of green, blue or yellow are available and “movement” in the form of imperfections such as striations, reams and small bubbles contribute to its appearance. This movement can vary in its intensity depending on glass type and manufacturer.
No Alternative to the Use of True Mouth-Blown Cylinder Glass
Today, there are numerous products on the market developed to replicate the appearance of cylinder glass, most typically for use in sealed units. To a greater or lesser degree, they achieve this as they provide the desired uneven surface reflection. However, for those seeking an authentic, hand-made material that is honest in its production and aesthetically true in appearance, there is simply no alternative to blown cylinder glass.
Having carefully considered numerous samples, the decision was taken to use Lamberts “DLAM” – a clear cylinder glass with minimal “movement” and a brilliant sparkly clarity. Supported by detailed section drawings and photographs, written documentation was submitted to the local authority for listed building consent and relatively swiftly granted.
Project Scope & Methods
With eighty five separate lights in total, a rolling programme of deglazing, studio based production and site based installation was carried out on a room-by-room basis. To provide essential ventilation, each of the properties many rooms was assigned a minimum of two opening windows. Traditional steel metal opening casements (galvanised and powder coat finished) were manufactured and supplied by a trusted and long serving supplier with all remaining none-opening leaded panels direct-fixed into the stone. Each of the individual panels included the addition of horizontally fixed saddle bars – essential for providing structural support. Hydraulic lime mortar was used to form a natural, durable yet breathable seal between glazing and stone and on completion, each panel was detail cleaned to a mirror-like finish enhancing the subtle qualities and natural beauty of the cylinder glass.
Conclusion
Through a combination of steadfast commitment to historic and aesthetic authenticity by the client and the hundreds of hours of traditional, hand-crafted work invested by the Lightworks (both studio based and on site), this project demonstrates how a period-sensitive approach, using historically accurate materials and techniques, can significantly enhance the appearance and heritage status of a listed property. With careful planning, expertise and a collaborative effort between the client, contractor and conservation authority, we achieved a cohesive, functional, durable result (leaded lights have a natural average life cycle of anywhere between 100 – 200 years) that has contributed towards re-establishing and preserving a wonderful old building’s historic character for many generations to come.
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