Moravian Preservation Master Plan.indb - Society for College and ...

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Moravian College • Preservation Master Plan still vulnerable to decay. All stone can be damaged by salts, freeze/thaw cycling, inappropriate or hard mortars, harsh chemical or abrasive cleaning, and improper coatings. The local stone used on many of Moravian’s buildings contains iron ore, resulting in staining reactions between the stone and rainfall. Limestone is used as trim material for window sills and surrounds, water tables, capstones, and steps. Indiana limestone is a buff-colored homogeneous limestone with few mineral inclusions. It is so regular in color and texture that it can easily be confused for cast stone. The fineness of Indiana limestone makes it ideal for carved sills and capstones. Slate is also sometimes used for terraces and steps. Slate is a metamorphosed sedimentary rock that tends to delaminate along natural bedding planes. Slate is a durable paving material, but is susceptible to deterioration from salts. Brick Brick construction is used for the majority of historic buildings at Moravian College, and is used as ornament on some of the stone buildings. Bricks vary according to their composition and manufacturing process. Early brick making technology produced bricks of varying quality. The quality of the brick used in historic buildings varies considerably, depending upon the materials used, shaping methods, firing quality, and other manufacturing considerations. The better quality bricks were used for exposed, exterior brick. The softer, salmon-colored bricks were used in the construction of inner walls or exterior walls that were meant to be covered with stucco. Like a loaf of bread, bricks have an outer crust and a softer inner material. Without the outer crust, the inner brick is vulnerable to rapid deterioration. Removal of the outer crust by harsh abrasive or chemical cleaning greatly reduces the durability of the original bricks. Brick functions best when laid with bricks of a similar type and with a mortar mix that is carefully matched to the brick type. It is important that brick masonry be protected from water infiltration through adequate roofing and site drainage. Bricks are porous and can absorb moisture much like a sponge. Water infiltration can cause freeze/thaw damage to bricks in cold weather. Water from the ground can carry salts in solution into the brick masonry, which can cause internal stresses as the salts form during evaporation. Waterproofing coatings are not recommended for brick masonry. They are often responsible for trapping water within the masonry rather than keeping it out. Individual brick units may be damaged by the corrosion of embedded metal elements and structural stresses. Embedded metal materials, such as structural steel angles, metal anchors, and through-wall pipes, will corrode in the presence of water. The expanding corrosion products have enough force to crack brick units and even seriously disrupt brick masonry. Structural concerns, such as settlement, may shift an entire wall causing cracking through brick units and joints. Any masonry disruption creates new avenues for water to enter the building, which leads to further deterioration. Typical Masonry Conditions Historic masonry conditions throughout Moravian College’s campus are good overall with some serious, ongoing masonry deterioration. Water infiltration of masonry is widespread throughout Moravian College’s historic buildings, caused by problems with both roof and site drainage. Affected areas show mortar loss, biological growth, and rising damp at the base of walls. In combination with salts and freeze/thaw forces, water infiltration has caused wholesale disintegration of stone and brick units. Masonry is further disrupted by structural movement, which causes settlement-type cracking through both joints and stone or brick units. Masonry has also been damaged by HVAC and electrical alterations. At some locations, vents have been cut through the existing masonry walls during HVAC upgrades. This work has disrupted the surrounding masonry, which has been inappropriately repaired in several cases. Electrical cables have been directed out through holes in the masonry walls and strung along the face of the buildings. These conditions could be avoided through more sensitive and holistically planned renovations. Masonry Inspection The best course of action to maintain masonry is cyclical inspection and repair. A yearly baseline inspection should be comprehensive and examine building exteriors and interiors, particularly in attics and basements. Water penetration is the major source of masonry damage. Although masonry is a John Milner Associates • October 2009 • Chapter 9 • Building Guidelines • 284
Moravian College • Preservation Master Plan durable material, it is still vulnerable to decay. To remain in good condition, the masonry wall must be structurally stable and weather tight, while also allowing enough flexibility to accommodate seasonal movement and remaining breathable. Inspections should include a comprehensive survey to identify potential problems. Exterior masonry inspections should be conducted in tandem with a complete roof drainage system inspection. Evidence of any of the following should trigger further investigation or remediation: • Leaking, broken, or overflowing roofs, gutters, and downspouts. • Soil erosion, lack of splash blocks, negative • drainage. Ponding and underground drainage problems. • Rising damp (moisture migrating up from sub-grade/foundations into masonry walls causing efflorescence, staining, and delamination). • Biological growth, staining, or efflorescence on walls. • Invasive vegetative growth on or near masonry surfaces. • Quick-fixes such as caulks and sealants. • Mortar erosion, mortar failure, and open joints. • Cracked masonry in conjunction with hard cement-type mortar. • Uneven weathering. • Mechanical injury. • Spalling and damage from deicing salts or other chemicals. • Spalling or buckling caused by movement. • Differential building settlement. • Cracks through masonry joints or masonry units caused by movement. Causes of Masonry Deterioration Water Infi ltration Water infiltration is the most common causes of masonry deterioration. Water is the usual culprit; it erodes joints, carries salt into the masonry, promotes biological growth, and causes freeze/thaw stresses. Water can penetrate walls from above because of faulty roof drainage or from below due to rising damp. Regular inspection of roofing systems and site drainage in conjunction with inspection of masonry walls is the first line of defense. Efflorescence is a whitish stain on stone or brick that is the result of crystallized water-soluble salts. Widespread efflorescence on an historic wall indicates moisture penetration. Inappropriate chemical cleaning can lead to efflorescence, as can chronic moisture from clogged or inadequate roof and site drains. In these situations, diagnosis and remediation should be undertaken to resolve the underlying problem. The most serious efflorescence problems at Moravian College can be seen at the back wall of the Steel Field Grandstand bleachers. A common problem at Moravian College’s historic buildings is dampness at building foundations caused by problematic roof drainage combined with poor site drainage. This is directly related to damaged, clogged, or missing gutters, downspouts and underground drains, which result from a lack of maintenance for these drainage systems. Eroded mortar, efflorescence, biological growth, and rising damp are symptoms of an underlying moisture problem. Water is absorbed by the wall and drawn upwards through the masonry pores by capillary action. Water then gravitates to the masonry surface where evaporation occurs, resulting in a characteristic tide line of wet masonry at the base of the wall. Biological growth will form on the surface of chronically damp masonry. In addition, water that is drawn from the soil into the building wall is laden with salts. These salts evaporate out of the water at the point in the wall where the rising damp stops. Here, salts will form just under the masonry surface, damaging the microstructure of the masonry from within. It is important to identify the cause of any deterioration that is found and undertake appropriate repairs. Repairing the masonry alone will not fix the root of the problem, and future masonry deterioration will be inevitable. Vegetation Moss or biological growth on masonry or adjacent soil surfaces is a sure sign of long-standing moisture problems. This is commonly seen in buildings with poor roof and site drainage and is seen on many buildings at Moravian College, particularly in shady areas or between closely spaced buildings. The roots and tendrils of moss, lichens, and other John Milner Associates • October 2009 • Chapter 9 • Building Guidelines • 285
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