Sometimes the best way to build with the environment in mind is not to build at all. Beautiful stone buildings that are already standing offer a great way to act on the mantra, “reduce, reuse, recycle.”
Restoration reduces consumption of new resources, reuses an existing structure, and recycles materials, including architectural and decorative treasures that would otherwise be lost forever.
Stone buildings were never intended to be disposable—masonry construction is meant to last. Extending the useful life of a stone building with thoughtful restoration and preservation gives us a more sustainable future, a connection with history, and an appreciation of the accomplishments and craftsmanship of the past.
As good as new
One might ask, can old buildings be made to perform as well as new ones? Efficient heating and cooling are among the biggest challenges (and opportunities) for making an historic stone building green. Drafty old buildings waste energy. Restoring stone walls and mortar joints properly can make buildings airtight so they can be heated and cooled as efficiently as new buildings.
The key to stopping air leaks in historic buildings is to use materials compatible with the original ones. It is important to match the structural integrity and appearance of original mortar. Filling cracks with any old bag of cement will not do the job, and it could actually make things worse. Samples of the old mortar should be tested in a lab so it can be replicated.
Matching the color and texture of original mortar is a matter of using aggregates of the same size and color in a cement matrix that also matches the original color. The best place to find matching materials is close to home. Most masons working 100 years ago did not have access to exotic materials from faraway places. They used what they had on hand, so a local quarry is the best source for matching sand.
Sometimes restoration experts need to be more resourceful. Denver-based Building Restoration Specialties Inc. (BRS) is restoring a granite structure built with mortar that contains granite flakes. To get a match, BRS collected granite from a nearby hillside, most likely the same source a century ago, to grind to the appropriate size.
Keep in mind that the mortar joints must be softer than the stone so if there is a failure it happens at the joint, not in the stone. Cracks in old stone buildings happen most often at windowsills and caps, where movement stresses the joints, allowing water infiltration. This compounds the damage.
Adding usable space to an historic structure creates another opportunity to increase energy efficiency. Often the best way to add space while maintaining historic appearance is to remove the roof and build up. When the roof is replaced, high R-value insulation can be added for energy efficiency comparable to new construction. Insulation can be added above a new ceiling or, if the owner wants to expose details like heavy timbers and beams, it can be added on top of the building.
If a project involves removing the roof from a stone building and building up, the contractor must evaluate the structure to ensure it can support the additional weight of a new level. He must study how the roof ties into the walls and take appropriate measures to make sure the walls can remain standing when the roof is removed.
Restoring old stone buildings does more than return them to their original beauty. It is also a chance to make them better than new by improving insulation and weather- sealing joints and windows. Masons specializing in restoration can also help general contractors and owners make these building components more energy-efficient.