When repairing the exterior brickwork of a historic Dresden home like the Moran House, you cannot simply use modern cement mortar from a hardware store. Old clay bricks are much softer and require a traditional lime-based mortar to allow the walls to naturally breathe and expand with the changing Tennessee weather. If the modern mortar is too hard, it will actually crush and crack the historic bricks over time. It is a very delicate, highly technical chemical process to get that mixture right.