Facade question -- Jahn mortar versus traditional stucco?

I am a preservation mason for 30 years who has used all the various products on the market for brownstone facade repair. I discovered Natural Hydraulic Lime based mortars and the stone repair material based on it about 14 years ago. I fell in love with it and never went back to other products. I understand that in NYC there are great craftsmen doing beautiful work and they possess the skills. However using stucco that is cement based and colored is not the best option and costly if it fails over time because the cost of labor is the most expensive element in the repair usually. My opinion is that they should just switch out what they have on their hawks and use the breathable Natural Hydraulic Lime based material that we have. The failures with cement stucco, and even the proprietary stone repair materials that are based on Portland cement and Natural cement, is that if a thin layer of frost gets under the coating, the moisture will push off the patch. Portland cement and Natural cement based repair materials may not breathe to a level equal to or greater than the brownstone thus acceleration the delamination of the coating. The repair material needs to have a greater liquid and vapor permeability than the host stone for it to work long term. Moisture does not always come from the outside either. There are air exchanges from heated air carrying water as a vapor through these sandstones on a very imperceptible level that can build up under a dense patch. As craftsmen we are very proud and possessive about the work we do and try to be true to the honor of the trade. Word got out that I imported such products from France to Allentown, PA where I warehouse these various lime products so I started LimeWorks.us to sell such materials. We still maintain the crews that do the work but also offer training utilizing the skill my guys have if that were needed. So, if you want to consider this a sales pitch or an honest and technically sound answer please consider that the repair material that I offer called Lithomex. I believe it is the best product in the US, that I am aware of, for brownstone repair. I don’t market heavily or have been in the mainstream for material supply since my main company has been conscientiously keeping our noses to the grindstone and attending to our work restoring masonry buildings. My wife saw this post and forwarded it to me so I thought my insights might be helpful. Regarding cost: I purposefully set the price of Lithomex at a fraction of what cement and natural cement based repair products for brownstone go for because at heart I am one who really does enjoy the beautiful architecture we have as cultural heritage and I do not want to thwart the repair and preservation of these buildings or just have material for the elite to afford. I price it so that it is affordable even though imported from France. I have a short video of a beautiful brownstone we restored using Lithomex at http://www.youtube.com/watch?v=lv_r2QdKZxs&feature=c4-overview-vl&list=PL152B735629294DBB Also using your smart phone and holding it up to the brownstone will allow you to see images of the stock colors we have of Lithomex if you go to limeworks.us and click on recipes and colors and then any one of the buttons will go full screen on your phone so you can see if what we have looks close, (of course the light setting on your screen and other factors can throw this off). Best to use the ‘send us a sample form’ and when you send us a sample we will call you back at no charge with an observation of how your stone compares with any of our stock colors. Sincerely, Andy deGruchy

To answer my own question, for the benefit of others: Jahn is vastly more expensive than stucco and likely unnecessary. It is a better product, technically, but not worth the additional expense, IMHO. Rather, if one applies stucco correctly and conducts proper inspection and maintenance, stucco should last fine.

We worked closely with Landmarks on a restoration in the Upper West Side and selected Jahn as the product manufacturer for both the brownstoning and the masonry grout.  I was pleased with Jahn’s product information in their specs, and LPC was happy to see a product they were familiar with be used. Also from discussions with the Brownstone contractor they were comfortable working with the Jahn product. www.agenciegroup.com