Moss Rudley is an Exhibit Specialist at the Historic Preservation Training Center in Frederick MD. He manages a team of specialist who travel the country restoring our nation’s built heritage. LimeWorks.us had a chance to speak with him in Gettysburg on his thoughts about using lime mortar in today’s environment of historic restoration.
My name is Moss Rudley, I’m an exhibit specialist with the National Park Service Historic Preservation Training Center located in Frederick Maryland. I supervise 18 craft people mostly masons and mason related activities. We do a variety of building construction throughout the United States in the National Park Service system and other federal agencies. The work that we do can stretch anywhere from Hawaii or Alaska, anywhere in the continental United States. Wherever a historic site is that might need our services. We’re non-appropriated through congress so all of our work is generated through projects that we take on and develop with our clients.
Thoughts on Natural Hydraulic Lime
We found that Natural Hydraulic Limes tend to be very user friendly for us. We go through a lot of them at times, and some might question our use in that from a cost standpoint but we feel that the historic sites are better off for doing so. Historic masonry was designed to create a whole building envelope that worked in system and when you start to change one of those components i.e. changing the mortar it can have a detrimental affect in a variety of places.
Working With Natural Hydraulic Lime
We’ve done numerous projects in Harpers Ferry and over the years, a lot of the brick structures that have had Portland put in, not necessarily by us but we’ve had to come back and redo work that has where the substrate, the brick has actually spalled out due to the inability of the mortar joint to pass moisture through them, the inability of it to breathe properly through the walls. Even in circumstances where we’ve run into where it’s been specified by an architect or an engineer to be used on a particular job. Just the lack of knowledge by the contractor, the lack of experience, the lack of exposure makes them not trust it either. There was a circumstance in Harpers Ferry where NHL was specced for stucco mix on a building. It then, the contractor came to us because of a mutual friendship between a couple of employees and asked us to give him a quick lesson on it. However they didn’t believe that it would set up upon its own and they used it in a context of as simply an add to a Portland mix. I believe it was NHL 5 that was specced in that job, or 3.5 I can’t remember. But they didn’t believe that just mixing that with sand would provide them with a product that set. So on their own they modified the mix and changed it.