And I am just a civil engineer who gets to play with stuff! Three of my favorite subjects but I will be brief;

 

• Coatings
• Brownstone
• Micro abrasives

 

Coatings whether liquid or cementious are not the problem, when handled properly. It is the rate of moisture vapor transmission through the interface or impregnated layer that makes the difference. Consider 3 pounds of water per 100 square feet traveling out of the structure during the winter (analogy used based on my ASTM work with debonding flooring materials where the 3 pound rule holds strong). As the moisture travels in vapor or moisture form ANYTHING that will impede the flow will, by definition, have to cause a buildup of this excess at this point in the structure. As this moisture continues to build up (3#’s reduced to 2.5# equals .5# buildup every 24 hours for example) at the interface or barrier, as it always seems to be within the freeze zone as it is close to the exterior surface, the 4% rule takes over (Water to Ice expands 4%) and the weakest of the components typically fails, the brownstone under layer! Stucco brownstones with pretty but totally inappropriate score lines which never mate up with the actual stone, age good for a maximum of 15 years in NYC, Period. Pages of additional data and opinions withheld due to my sympathetic nature. Final note; If a stucco, typically European previously, is applied and is less dense, for the lack of a better tern, and is more breathable this is a case where an applied stucco will work. Northern Germany uses brick as a base for stucco. (softer over harder – case in point)

 

Brownstones – see above, but I will add a few comments. Having been involved in the repair of brownstones for over 15 years and having used at least 4 different proprietary mixes and witnessed at least 7 different materials used I do believe that under the right conditions which primarily depend on substrate condition and the ability of the stone to actually perform in the application intended, patching is a very viable alternative. However, based upon my importation of natural brownstone I would like to dispel the myths that there is no quality brownstone available for repair, restoration or in fact new structures. Also brownstone makes an excellent landscaping material when the right material is made available. I have seen ground contact brownstone in perfect condition with installation dates going back to the 1200’s. I will stop but along with my partners this is one of our favorite subjects to discuss.

 

Micro abrasives – First, if you don’t know the difference between JOS and Rotec in both design and performance the rest of this may be academic. If you think they are the same, please don’t specify micro abrasives on sensitive materials. Micro abrasive ranging from the abrasives included in Sponge Jet material right through to the hydro abrasives (sandblasting with water) should always be at least consider then eliminated individually based on the projects needs and the systems properties and capabilities. Baking Soda works great on steel but do you really want to use it on a masonry project with substantial mortar?

 

I only bring up the above for continued discussion and concur whole heartedly with Ken, and most of the time with Mike.

 

Thanks for the opportunity.

 

Pat M

 

 

Edison Coatings wrote:

I am just a chemical engineer

And I am just a guy that gets to play with stuff.

I agree that control of water flow through maintenance of gutters, leaders, roof systems etc. is way more of a factor in the deterioration of brownstone facades than coatings. Though I really am solidly against the wholesale use of cut-n-stucco techniques.

I have encountered situations, one in particular, where the sandstone (not brown in this case) was coated so many times by maintenance staff that it was the coating that held the stone together. Once the coating was removed the stone crumbled, whereas everywhere else on the facade where maintenance could not conveniently reach the stone was in noticeably better, though admittedly poor, condition. So, I would prefer appropriate maintenance if it is to occur at all. In my experience though knowledge is not very well communicated to maintenance. Which brings up questions as to how knowledge of anything gets disseminated into the built environment. Many times experts are not brought in to see evidence in the field as there is no motivation to involve them -- then the question is how do they learn?

If you don't have tons of water pouring into the wall system, letting it out just isn't that big a deal.

Yeah, all you need is good flow, a few well placed holes.

...they just aren't seeing the predicted damage. DUH! But hey, don't acknowledge those of us who questioned the conclusions on this subject 25 years ago.

I agree with your sentiment re: the back-n-forth on clear coatings. It is curious to me that a quarter century can go by and yet there is no conclusive consensus. One expert doctor will say it is good to beat children, another expert doctor will say that it is not. Personally I find the lack of consensus, and the constant reiteration of pro and con to be the more interesting subject.

I remember a time when to say 'abrasive blasting' was suicide and that was when I was playing with plastic media to remove epoxy paint from granite at Carnegie Hall. Then came micro-abrasives and soda blast and all sorts of chummy stuff.

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