Masonry Restoration Explained
Article written by Marty Smith
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 amongst 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 repointing. (This, to me, 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. I am quite sure that some mason is going to get ahold of this ruminating and debate me on it. (It didn’t have to go far. The mason at the desk next to me began the debate immediately upon reviewing this article.)
In the Greater Puget Sound area, 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 categorizations…reinforced and unreinforced. An unreinforced 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. These are the buildings that fell apart during the Nisqually quake in 2001 (Link).
As stated, most masonry buildings in the Puget Sound area are merely brick skins. In other words, they are stick or steel frame buildings with brick veneer on them. Having said that, 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 repointing 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 repointing 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.
In the Greater Puget Sound area, with our history being not nearly as long as the East Coast, or Europe for that matter, mortar compounds are significantly harder on our buildings than in other (older) 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 70s) that Portland cement was shipped into the Northwest around WWII in order to make concrete barges to get materials to the Pacific war front. I have no idea if this is true, but it was a good story and I am 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 Northwest has evolved considerably over the last 50 years.
When I started in the trade we were pointing the old lime mortar joints with very hard cement mortar compounds. 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 I 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…again.
In the Puget Sound region, since we got another of Mother Nature’s wake up calls in 2001 with the Nisqually quake, the requirements that are coming for seismic retrofit have been passed and it is just a question of time before all masonry buildings of a certain age are going to require some form of upgrade. The new requirements are now in place and there is a 10 to 20 year deadline to get compliance on these requirements.
There were over two years of talks and debates in the city planning office among leading engineers, seismologists from the University of Washington, and the city representatives from various building departments. What has been put into place, as of late, are rules that primarily have to do with unreinforced masonry buildings (URMs). These are structural masonry buildings that meet the criteria explained above. Those that have had some retro work done on them will have fewer requirements than those that have never been upgraded. The system being called for is thought of as a minimal system, not intended to keep the building in workable shape after a significant seismic event, but more to make sure that the floors stay together enough that everyone walks out of the building after an earthquake. It is called a Bolts Plus system (Link). In essence, it requires that all the floors and roof lines be tied to the masonry, and that the sheer of the roof and certain floors be changed. There are a number of other requirements, but, in essence, these are the things being done.
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 I 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. I 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.
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. I can’t tell you the number of times that one of my leads has 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.
There is a fine line between restoring and harming a building. I will give you an example. The high school I went to is a grand old Seattle building (that shall remain unnamed…but it sits on a hill above downtown). The Seattle school district sold the building to developers about 30 years ago. Since then the building has been cleaned and sealed twice, with another round of cleaning and sealing coming in the near future. It is a significant job for a contractor as the building is pretty large. It is comprised of a soft pressed brick and limestone. When I was going to school there, the building was about 90 years old. It was kind of a mid-gray building, and everybody there just thought that was the color of the stone. It was a grand old building and we were fond of the old girl.
Then the private developers cleaned it with high PSI pressure washers. They scrubbed hard on the fluted columns on the front of the building to get some graffiti off. Since that time it has been cleaned again. The detail of the carved stone is rapidly fading. The fluting on the front columns is disappearing. The building is being wrecked…all for the sake of wanting an old product to look new. It breaks my heart. The lifespan of the building has been significantly shortened by the short-term dollar. Let’s face it. They don’t build them the way they used to, and sometimes our best intentions are not what is best for the future generations.
Again, a good restoration mason knows the difference, and a truly great mason will not sacrifice the integrity of a building for a quick buck.
Find that great mason.