Masonry Restoration Explained
Masonry restoration is the phrase used for working with any form of masonry on an existing building or home that does not encompass actually building it. Restoration runs the gambit from tearing the masonry down and rebuilding to cleaning and sealing.
Typically, masonry restoration is thought of in terms of tuck pointing, which, in itself, is a misnomer. Tuck pointing is a term for adding to a joint and it’s not what is typically thought of in the restoration process. There is a great deal of debate among-st the talking heads on the blogs and LinkedIn sites about the definitions, but suffice it to say, the proper term for removing a certain amount of mortar from a joint, and then replacing it with new is, technically, called re-pointing. (This, to us, also does not make much sense because any term that begins with “re” indicates that it has been done before.) In most cases, when the masonry on a building is restored, it is for the first (and hopefully the last) time. Therefore, to me, the term “pointing” should be used. We are quite sure that some mason is going to get a hold of this ruminating and debate me on it.
In Michigan, most brick buildings are, typically, frame buildings that have masonry “skins” veneers on them. There are a relatively few buildings that are true masonry buildings. The definition of a true masonry building is this…if the floor(s) and roof are held up by the masonry, then it is a structural masonry structure. Most of these types of buildings are concrete block (CMU) buildings, and typically do not go higher than two stories. They are the (relatively) older buildings that you find in the industrial parts of town that are populated by warehouses and small businesses. (The cells of the CMU are not poured solid completely and there is not much steel in the cells, thus they were not valued for buildings higher than the two stories.) Now, most of these buildings are constructed with “tilt up” panels. There are, however, a number of brick masonry structures in the area that follow the criteria of structural masonry. Of these, there are two categorization - reinforced and unenforced. An unenforced masonry building is one that has never had any retrofit in order to tie the walls to the floors, and it has not had the parapets tied back. The restoration process on the exterior surface of a masonry skin and the exterior surface of a structural masonry building are about the same. Though re-pointing the exterior of a masonry building does help the structural strength of the masonry, the primary objective of pointing masonry is waterproofing. In other words, the re-pointing process is more about sealing the masonry joint than about adding strength to the structure. If the integrity of a masonry structure is compromised, pointing the structure does not do any good. It might look good for a short amount of time, but if the structure of the masonry has failed, there is nothing you can do but rebuild or retrofit it.
Here in Michigan mortar compounds are significantly softer on our buildings than in other (newer) parts of the world. Without going into the entire history of mortar, it is sufficient to know that in this area Portland cement being added to mortar is a relatively new idea. Prior to WWII masonry structures here and elsewhere were primarily built using lime mortar with very little, if any, Portland cement in the mix. Note that the name “Portland” has nothing to do with Oregon. The name comes from the materials similar to Portland stone; it was originally developed in Britain in the 19th century.An older mason once told me (in the 70's) that Portland cement was shipped into the Northwest around WWII in order to make concrete barges to get materials to the Pacific war front. We have no idea if this is true, but it was a good story and we're sticking to it. (I was a young tender and he had been in the trade for about 40 years at that point.) Either way, lime based mortar is considerably softer than cement based mortar. The restoration processes in the Northeast has evolved considerably over the last 50 years. When we started in the trade we were pointing the old lime mortar joints with very soft, lime-based mortars. Since then the restoration mortar types have softened to the point where it is now the common-thought that masonry restoration should be performed with lime mortar. However, the most common type of restoration mortar used is called type N, which is 6 parts sand to 1 of lime and 1 of cement (type N). When we started in the trade it was 4.5:1/2:1 (type S). Type S is the typical type of mortar used in much of the new masonry construction, at least in this area. However, there is a trend, even in new construction, to soften the mortar, not only in new construction, but also in restoration. Added lime and less cement creates a softer, more flexible bond, thereby actually increasing the seal of the wall. Obviously, buildings are built differently now than they were 100 years ago. Masonry buildings were built with the idea that they were the waterproofing component themselves. Brick was softer, mortar was softer. Buildings absorbed water when it was wet, and released it when it was dry. As time went by and technologies developed, the theories of structure changed. Building skins became far more rigid (more type S). In so doing these types of veneers became less water absorbent, thereby necessitating sealant technologies to create an envelope system that is independent of the masonry itself.
A good restoration mason is a magician,or so it seems. He, or she, can take an old, worn-out building and make it look as good, if not better, than it did when it was new. Though masonry is probably the second oldest profession there is, the methods being used in this trade are not all that different from the masons’ of the Roman Empire. The primary change is how much more easily the materials get to the job site, and the method by which the masons get to the wall. Not long after the first masonry structures were built, masonry restoration began. In today’s market, a good restoration mason knows the difference between how a building was built 100 years ago compared to a building built 50 years ago. Today’s thought process in terms of restoration is quite different than it was even 20 years ago. The funny part is, the more we know, the more we are going to the ways of old. So, not only does a good restoration mason understand the difference between the methods used to restore a 150 year old building with that of a 75 year old building, they also understand how to take an existing masonry structure and make it as economically safe as possible within the parameters of the value of the building. Being honest, some buildings just don’t deserve to stay up and, for economical and safety’s sake, should come down. Yes…even some old, wonderfully ornate masonry buildings…because they are dangerous. The things we have seen in old buildings lead me in one of two ways…perfectly content and safe in one…or horrified and refusing to enter the building…at all. Most people have no idea what they are walking into.
There is currently a debate raging as to whether a masonry building should or should not be sealed. We weigh in on both sides of the subject and my opinion is based on the circumstance and the building type. The opinion of the purist restoration folks is NO…never use water repellents on any type of older masonry…but I do not completely buy into that. Most Historic masonry restoration projects could use a repellent. As a masonry restoration contractor, we recommend ChimnySaver Water Repellent on 90% of our projects. Chimneysaver is backed by a 10 year warranty.
Some of the water repellent compounds are getting so advanced and are significantly improved over what they were even five years ago, thus there are specific applications on older masonry structures that actually significantly add to the longevity of the building. However, for the most part, we, as restoration masons, have followed the lead of the suppliers and the architects/engineers. When we started to think for ourselves, there were a number of things we changed…hence the ideas that the old buildings (built by real craftsmen) were done so for a reason. The arrogance of this generation not seeing the brilliance of those who came before us is not only dangerous to our heritage, but just plain ignorant. Masons of old did not have the same types of tools we have now, and to see what they could do with the materials they had often astounds me. We can’t tell you the number of times that one of my lead-masons have called me down to the job just to show me how something went together once they had opened it up. Not only were their methods effective, in a lot of cases they were quite ingenious.
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