Traditional Masonry Archives

Architects Corner: A Tale of Two Buildings
Meticulous attention to detail was key in the renovation of two historic buildings on the Amherst College campus. On-site training in historic masonry techniques and the use of traditional materials were essential components of the job.
by Geoff MacDonald

South College (1812) and North College (1823) are two of the original buildings on the campus of Amherst College, in Amherst, Mass. Along with Johnson Chapel, situated between them, the buildings form the centerpiece of historic College Row.

The buildings interiors' were renovated in the 50's, but the exteriors had not had any significant work since the buildings were initially constructed. Both the brick and the mortar were at varied degrees of deterioration and in desperate need of restoration.

The exterior restoration work consisted of repointing the entire exterior façade and selective replacement of masonry in the exterior bearing walls. Because North and South are so significant to the College, the work was to be meticulously detailed to maintain the building's historic integrity and then carefully restored using traditional materials. For all involved, the project has been a success!

But the real story was the journey to get there. Like most successful projects, it started with a team of players with drive and enthusiasm, a common goal, the ability to work together and the experience and knowledge for the task at hand.

The Building Owner: Sensitive to the aesthetic value of the original architecture, the owners wanted the buildings to look as they did 180 years ago. They wanted the materials to be historically correct and to be consistent with the original size and color. The College demanded quality workmanship and steady progress.

The Architect: We started by thoroughly investigating the buildings' exteriors and documenting where the mortar was cracked and flaked and where there were missing and spalling bricks. This data was used to develop comprehensive drawings that accurately detailed the scope of the masonry reconstruction. In an effort to ensure the best bid results, it was decided to issue the drawings in color. The exterior elevations were specifically called out in a variety of colors and patterns showing areas to be renovated. Individual bricks were clearly identified for replacement, so the contractors could determine the amount needed. In addition large areas to be rebuilt were accurately colored to provide the contractors with square foot quantities.

While the drawings were being developed, samples of the existing mortar were sent to U.S. Heritage Group in Chicago for analysis of the aggregate color, particle shape and grain size distribution. This was a critical step in determining the mix proportions of the major ingredients used in the existing mortar sample. The sample's physical characteristics, the buildings' original date of construction, and guidelines from the National Park Service were used to determine the proposed mortar component recommendations as well as the aggregate ratios for the replacement mix. From the results of the study, U.S. Heritage developed and, after the College's approval, provided the mortar for the repointing.

Brick procurement was not as scientific as the mortar. We obtained a large number of sample boards from different brick suppliers and compared them for color and texture to the existing brick. When we had a few that looked good, we requested full-size brick samples to compare their physical size to the existing brick. After reviewing the proposed brick with the owner, the acceptable brick was ordered.

The Contractor: The contractor was asked to bid on the restoration work with three other pre-selected and pre-qualified contractors. Because they all had the expertise and references to do the work, the "low bid" contractor was selected without concern. However, as important to the project as using appropriate materials was ensuring that the individuals doing the work were qualified craftsman. To ensure both the historic appropriateness and the cost-effectiveness of the restoration project, the college required on-site training of the masons performing the work.

During the on-site training, proper techniques for replicating the original joint profiles and mortar finishes were taught. Proper repointing, finishing and curing techniques were established and defined, and the masons practiced under supervision. In addition, a mock-up sample was installed on the building and used as a benchmark to be referenced throughout the rest of the work. This training enabled the masons to become comfortable with the materials and the required application techniques, which meant better quality of work and enhanced efficiency.

The Moral of the Story is threefold:

• Detailed drawings. Taking the time to painstakingly investigate and document the buildings' existing condition allowed for a clear and concise set of construction documents. The extra care taken to develop the detailed drawings allowed for excellent bid results and clear direction for the contractors to do their work.
• Compatible materials. Material compatibility means that the repairs will behave in the same manner as the existing structure, in essence becoming one with the building. The repairs will expand and contract with the masonry, and will be breathable enough to allow water vapor and liquid water to escape to the surface. As a result, the repair will not fail due to freeze/thaw cycles. In addition, the mortar and brick match up or blend in with the original architecture to become aesthetically agreeable.
• Well-trained masons. Masons should be craftspeople. Specific training in historic masonry restoration is essential. A well-trained mason has been taught the proper application and finishing techniques of masonry restoration and clearly understands the workmanship standards specific to the project. The finished product is only as good as the persons performing the work.

Geoff MacDonald, a senior architect with Sacco + McKinney Architects in Latham, N.Y., specializes in historic renovation projects. In his spare time he likes to play golf, run and vacation with his family at Cape Cod, Mass.

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