The Association for Preservation Technology Northeast Chapter (APTNE) held its 2011 Annual Meeting and Symposium on February 4 in Boston. The meeting was well attended, with over 200 people braving the mid-winter weather to make it to the full-day event.

The theme of the symposium presentations was “The Use of Substitute Materials on Historic Preservation Projects.” Henry Moss introduced this topic in his excellent keynote talk, which raised thought-provoking questions about authenticity, transience and levels of substitution. Moss used examples from New England and the United Kingdom to illustrate a shift in thinking about replacing materials to replacing assemblies and the contributions of material sciences and building physics to the discussion of substitution.

Following the keynote presentation, two papers were given that presented the challenges and concerns in considering replacement materials from the perspective of local preservation planning commissions. Mary O’Neil, an Associate Planner with the City of Burlington, VT, and Catherine Albert, a recent graduate of the Graduate Program in Historic Preservation at Columbia University, presented case studies illustrating preservation issues related to replacement of siding and windows, respectively.

The next two presentations provided contrasting views on substitution, illustrating the importance of evaluating each potential treatment in light of the specific conditions, goals and needs of the project. Art Femenella’s case study of the restoration of a Lalique cast glass façade demonstrated why a substitution system was necessary in light of the design flaws of the original installation. The next presentation, on the repointing of historic brick masonry at Fort Jefferson, showed that after thorough analysis, numerous mock-ups and field applications of various mortar systems, the most appropriate replacement mortar was found to be the one closest to the original mortar.

The afternoon presentations reviewed a range of substitute materials that have been used to replace or in conjunction with historic masonry. John Fidler provided an update on his ongoing study of glass fiber-reinforced plastic (GFRP) substitute materials. Providing many examples of the use of GFRP in England, where it has been in use for 45 years, Fidler has drawn some conclusions after 30 years of observation. Based on visual assessment, painted GFRP adjacent to other materials that are painted may be acceptable, but other applications are typically undesirable. In addition, when considering the use of GFRP to replace historic masonry, other factors such as the mechanical and chemical properties must also be evaluated.

Michael Edison also took a historical view of replacement materials, demonstrating how composite patching mortars can be used as a substitute material for historic stone and terra cotta. As Edison showed in several case studies, cast-in-place composite repair mortars have a 30-year track record as a viable substitute material for replacement of masonry units.

Brent Gabby’s presentation on cementitious materials within historic masonry systems showed how a variety of substitute materials can be used as part of the structural system to help preserve historic buildings. Gabby used case studies to illustrate the use of poured-in-place concrete, pre-cast concrete, CMU, lightweight concrete panels and shotcrete. These materials can be creatively used as back-up, roof framing and to stabilize masonry so that the original or repaired masonry façade and architectural finishes are preserved.

Finally, Roy Ingraffia and Kyle Normandin introduced a restoration mortar that can be used to meet a wide range of masonry repair needs. Using marble repairs at the New York Public Library Steven Schwarzman Building and sandstone repairs at St. Mark’s Church in Philadelphia as case studies, the presenters showed how Lithos Arte can be trowel applied or cast in place and then sculpted and carved to create appropriate and compatible masonry repairs.

Overall, the symposium offered an interested selection of presentations, from the philosophical groundwork for substitution and preservation planning to replacement systems specific substitute materials. The lively questions and answer discussions after the sessions and during the breaks testifies to the success of the symposium.