I’ve been in the masonry restoration business for over 40 years. I have heard stories of architects, building owners, and contractors disillusioned with lime mortar, lime putty, and magic proprietary mixes that have all failed. The bad rap gets pinned on the use of “traditional historic and hybrid mixes” by the contractor and the manufacturer often blames the installer for the error. I believe they are both right. There are in fact many application errors in the industry because of incompatible materials used to make repair mortars, which when blended together using the wrong lime or when a Portland cement gauging is used to improve the wrong lime, fail due to the incompatibility of the repair materials to the substrate. The installer has an error which can’t be avoided.

The use of pure lime-based materials is not rocket science and has worked for millenniums. However, there will always be failures if care is not administered throughout the project. This should start with the specification of the right material for the corresponding application. If caring guidance does not start and end with the project then an unwanted outcome is going to be the result. In the end, it is the owner who finds they have to live with less than what they anticipated or they must fight a huge uphill battle to get what they paid for after the insult has occurred. The architect may then want to shy away from the future use of “difficult” materials or using the innocent contractors who didn’t generate the intended outcome. The contractor is always glad to go back to what they used to use since it served them well for at least what is their window of experience. No one wants trouble and no one can blame anyone for having these natural reactions.

Natural Hydraulic Lime, which is the basis for the repair material line of St. Astier mortars, has many appropriate applications that will yield an excellent service life for their respective applications if adequate diagnosis of where the application will be rendered and adequate training and follow-up for their installations is engineered into the project. In the end, the contractor will find out exactly how “user-friendly” the products really are. The architect and owner will be glad for the timeless beauty that will follow with the correct installation of the right product for the right application.