Rising to the Challenges of a Century of Deterioration

Project Background

• Church's buildings were constructed in the late 19th century from quartzite stone
• 85-foot bell tower is one of Bethlehem's most prominent structures
• Decorative elements include traceries, battlement caps, parapet caps, buttress caps, belt courses, and water tables
• A century of natural weathering, combined with acid rain, freeze-thaw cycling, and improper repairs, had resulted in severe structural deterioration

Project Challenges

• Upper level of bell tower exhibited large vertical cracks
• Parapet walls were bulging and bowing
• Battlement caps and decorative parapet niche stones were deteriorated beyond reuse
• Limestone traceries showed severe cracking resulting from steel anchor corrosion and the stresses of adjacent displaced masonry
• Acrylic water repellent previously applied to church walls had been degraded by UV light and had turned white
• Naturally occurring iron deposits within the quartzite had rusted and bled down the church's walls
• Certain quartzite pieces had turned into a powdery, crumbling mass
• Many original mortar joints were cracked, eroded, or missing
• Blue sandstone was exhibiting extreme exfoliation, delamination, cracking, and loss of detail due to improper bedding plane orientation
• All work was performed very close to busy sidewalks and a major vehicular thoroughfare

Project Approach

• Three tons of new steel beams and channels were hoisted into the bell tower and welded, bolted, and grouted into place
• New lead-coated copper through-wall flashing was installed
• Replacement battlement caps were cast using a coloring agent that would match the appearance of the original bluestone
• Tracery limestone pieces were removed and reset
• A combination of high-pressure water blasting and abrasive grit blasting was used to remove water repellent stains
• Iron stains were removed with an ammonium bi-fluoride solution
• Crumbling quartzite pieces were removed and replaced
• All surface mortar was removed and painstakingly rebuilt with a historically accurate high-lime mortar
• Damaged blue sandstone sections were rebuilt using a proprietary stone patching material
• All scaffolding was wrapped with heavy-duty netting to prevent any accidents or injuries as a result of falling debris