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Conservation And Preservation Of Stained Glass Nationwide
New stainless steel “T” mullion and terra cotta blocks. A stainless steel cross bar provides additional structural support. A lancet window with a new perimeter sealant joint.

Integrating Terra Cotta Window Mullion Repair
With Leaded Stained Glass Window Restoration - Part 3

St. Dominic’s Church, San Francisco

The Stained Glass Quarterly
by Lex F. Campbell; Simpson, Gumpertz, and Heger

Innovative Repairs & Project Planning

The large scale of the project and potential overall costs presented a dilemma for the church, that, like most organizations, had a limited set of funds available on a yearly fiscal cycle. Therefore, in order to spread out costs, it was evident from the very beginning that the project would be phased over a number of years. Furthermore, priorities would need to be set to address some of the more severe deterioration and potential life safety issues first.

During their overall survey, SGH noted the severity and extent of cracking at window mullions that ranged from all mullions being cracked at an individual window to none at all. The cracked window mullions could further be classified into blocks that contained open cracks and visible spalls, indicating more advanced deterioration. In the end, blocks that contained severe deterioration (i.e. open cracks and spalls) and mullions with all (or nearly all) the blocks cracked were assigned a high priority or Priority I. Windows that contained some severe cracking that was limited to less than five mullion blocks were assigned to Priority II. Windows with minor cracking in individual mullion blocks or no cracking were assigned a low priority, or Priority III.

The condition of the leaded glass windows provided additional direction as to project priorities, phasing, and planning. Windows were classified according to windows that immediately need releading (as directed by the glass conservator) and windows that should be releaded within the next 10 years and 20 years.

When mullion and window conditions were compared together, high-priority repairs were immediately evident in windows that contained Priority I mullions with glass that needed immediate releading. Window mullions with little or no mullion replacement and longer releading cycles were scheduled for work later in the repair phasing. This system was used effectively to prioritize and divide window repairs into phases that were manageable and affordable to the church, while addressing high-priority repairs first. Project delivery initially included the production of construction drawings and specifications for pricing and could be adjusted as needed to fit the church’s budget for the year.

Work proceeded at the south Nave clerestory first, followed by the south transept, apse, triforium gallery, east and north elevations, respectively. While all the windows and terra cotta on each elevation had unique requirements, various themes were consistently repeated throughout the project, revealing issues that are perhaps common to terra cotta tracery window openings.

The existing leaded glass windows originally were set in a mortar-filled reglet finished with a sealant fillet on the exterior and glazing putty on the interior. As is standard practice, the sealants and glazing were tested for hazardous materials..

All of the tested windows contained asbestos fragments within the exterior sealants. Due to its hazardous content, an abatement contractor that specializes in the removal and disposal of hazardous materials was required to remove the sealant. As part of this work, the abatement removal needed to be contained within a conditioned enclosure to prevent dust and materials from entering the outside air. Special training, protection, and certification were required to enter the enclosures during work. Due to the proximity of the work to the leaded glass and special access conditions, the question was raised as to how the abatement work would be accomplished, supervised, and coordinated with the glass removal.

For this project, which lacked a general contractor, the best solution was to specify that the abatement work be included as part of the stained glass restoration studio’s work. This meant that the stained glass sub-contractor would be responsible for supervising the removal of all materials around the glass, as well as removal of the glass, and the condition of the glass upon removal. In practice, the stained glass restoration sub-contractor brought in a hygienist to establish and supervise procedure as well as to provide the required training for being in enclosures. The stained glass sub-contractor also contracted the abatement contractor for removal of the hazardous material. The abatement contractor was closely supervised by the stained glass restoration sub-contractor to limit damage to the glass.

The Stained Glass Quarterly

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