By: Jimmy Monahan
If engineers or architects perform enough building envelope surveys or inspections, they will eventually come across buildings with stained-glass windows as a part of their exterior wall assembly. Most often, stained-glass windows are found in religious structures such as: churches, synagogues or mosques, or in hospitals affiliated with religious organizations. A majority of stained-glass windows that exist today were installed in the first half of the 20th century or earlier.
Stained-glass windows are unique and beautiful, but not immune to harsh exterior elements and the subsequent restoration that is required to protect a building. Obvious signs of stained-glass window failure include: lead fatigue, cracks in the stained-glass, filth and grime on the stained glass, and short-term repairs. If left untreated, these deleterious conditions can lead to prolonged moisture infiltration, resulting in the deterioration of interior wall finishes and/or the surrounding masonry. Unfortunately, it’s at this point when damage has already occurred that a building envelope consultant or stained-glass window expert is retained to access deterioration levels and determine necessary repairs.
Lead fatigue is a primary source of failure in stained glass windows. Over time, major storm events, systemic freeze thaw cycles, and exposure to the elements will cause lead joints to corrode or crack. This fatigue or failure in the lead joints will cause the window to bow inwardly or outwardly. If the bowing stained-glass is left untreated, the individual stained-glass pieces will crack. Additionally, stained-glass can also be damaged by hurricane winds, hail, or even vandalism.
General filth and grime are often the result of prolonged moisture and air infiltration. This condition is exacerbated in highly polluted and densely populated urban areas. In some cases, the existing stained glass is so dirty that its color cannot even be determined.
Besides the obvious aesthetics, another benefit of properly installed stained-glass windows is that they will last 50 to 80 years. However, having a building element for this long a period of time usually guarantees that the building will have different management, maintenance staff, and financial circumstances. Property managers, building owners or boards, especially during leaner budgetary periods, may opt to perform short term on-site spot repairs or stop gap repairs. For example, silicone might have been used to treat the cracked glass pieces, or window cement might have been installed at the lead joints to seal the gaps. These measures may temporarily treat symptoms, but do not address the root problems, and will often lead to more costly or difficult future stained-glass restoration. Proper stained-glass window restoration methods and recommendations will be covered in a subsequent article in our October newsletter. Another thing to keep in mind is that restoration of stained-glass is a unique niche, and t
hat it’s likely that your average window contractor is not qualified or approved by the Stained-Glass Association of America. Restoring stained glass is an art form and there are a limited number of contractors in any area that are qualified to do so.
Periodic building envelope surveys will identify early signs of stained-glass window deterioration before full scale restoration is necessary. Therefore, it’s imperative that building envelope consultants inspect any stained-glass windows and recommend any repairs as part of their report or survey. Regular maintenance of stained-glass windows will also result in lower restoration costs in the future. Building owners or property managers should never overlook the condition of their stained-glass windows until the point of potential failure, but rather, should retain a building envelope consultant to avoid headaches later on.