Sealing the Deal
You've just finished off that new masonry project and you're standing back and admiring it. A finished work of art. Work of art, maybe, but finished? Many experts feel that it's not time to pack up your toolbox until you've applied a water repellent to the surface of the brick or block.
We spoke with Jeff Erdly, President of Masonry Preservation Services, Inc., Past President of Sealant, Waterproofing and Restoration Institute (SWRI) and MCAA member, and he had plenty to say about the subject.
"You can take a wall that is well constructed and functioning, apply a high-grade, clear water repellent on it, and you can improve the performance of a good wall," says Erdly.
"I often tell clients that the time to put on a clear, water repellent is after we have repaired all of the deficiencies that make the wall leak. Once you have a wall that doesn't leak, there are certainly good arguments to apply a clear, water repellent. They can include, but are not limited to: protection of brick that doesn't meet severe weather grade; enhancing the ability to clean the wall down the road; and improving the appearance of the wall during wind driven rain events where it doesn't all wet out. There's a whole list of attributes that a high-grade, clear water repellent can bring to a correctly built, functioning wall.
"However, in our industry, when the wall doesn't work and the building leaks, the first thing that people do, or they run to for a quick and easy fix, is 'Gee, I'm going to put two coats of whatever on this wall to make it function.' It just doesn't happen."
There are quite a few materials out there to choose from. Erdly says, "You want a material that, chemically, has a molecule small enough that it can actually penetrate the pore structure of the wall of the brick and really create that hydrophobic area back in the structure of the brick itself. We want our waterproofing not on the surface of the brick, where it's going to be scoured, worn away and degraded by UV light, but actually within the masonry."
Some types of water repellents that will penetrate the pores of the brick and block include silanes, siloxanes and silane/siloxane blends. These types of materials can help protect porous building structures against water and water-borne contaminants and damage, such as freeze-thaw, acid rain, and growth of algae or fungi.
"The chemistry behind those materials, their molecular size, and their ability to penetrate the pore structure are much better than the surface sealers that form a rather significant seal on the surface, like the acrylic resins," says Erdly. "I'm not qualified to give you the analyses on the different chemical make-ups; there must be 500 different mixtures and matches, everything from snake oil down to stuff you can't even pronounce, which claim to make a masonry wall work."
So are we talking about waterproofing or water resistant systems? Erdly has strong feelings about this.
"The whole idea of a waterproof masonry wall, in my opinion, is a fallacy," says Erdly. "In the real world it simply doesn't happen."
Terry Wallace, Director of Chemprobe, Tnemec Company's Masonry Protection Division, agrees. "'Waterproof' is way over used in the commercial end; it should probably be a term that is never used. I just happened to read something in one of the BIA publications, and they actually said that they do not like the word 'waterproof' or even use the word 'waterproof' because, in essence, we just don't have systems that are truly waterproof.
"The definition that we follow in the industry — and that nomenclature can get people in trouble — is that we manufacture water repellents or water resistant systems. What we like to say is that we are part of a complete building envelope water management system. Surface-applied water repellents being one component of that, proper design being another component, and proper construction procedures being followed and adhered to is yet another. Mostly we're talking about single-wythe construction, but there is no doubt that these same concepts would also apply to multiple-wythe construction. It is however of the utmost importance when you have the single-wythe construction."
So whenever you're laying brick, you should apply a high-grade, clear water repellent, even if it's cold out? "Absolutely not," proclaims Erdly. "You can't have ice crystals formed within the substrate you're trying to penetrate. If you're putting a clear water repellent on a wall, you need a wall where the surface temperature is at least 40 degrees. A lot of these materials require a catalyst to make them become hydrophobic. They have to get on the wall and they have to react with constituents in the assembly to 'let the Genie out of the box,' if you will. Applying clear water repellents in cold weather, you're just asking for all kinds of problems. Unless you're building it where the temperature never gets real warm, you certainly need to be bright enough to understand the dynamics of not putting this stuff on until you've got a wall with a rising temperature.
"If you have a wall and it's really cold, how are you really ever going to get enough initial moisture out of the wall for it to be safe to put a clear sealer on it? We've actually had people who say, 'Well, we've done winter masonry, we had it all built in, and now we're going to put a clear sealer on it.' And I have to say, 'Why don't you let it go through the spring and let it bloom a little bit. Let's let the cements hydrate and all of these things happen before we try to get in there with some magic gunk.'" Wallace continues, "With the silane and siloxane materials, we suggest a temperature range of 40 degrees up to about 90 degrees — and that's substrate temperatures, and that's important due to thermal mass. If it's applied at substrate temperatures of 38, it's probably not the end of the world. Obviously, when you have a water-borne system, you can't really push that level."
So what differences are we talking about between water-borne and solvent-borne sealer systems? Wallace says, "It's really just the carrier that the reactive material is suspended in. Solvent-borne materials have been around a lot longer than the water-borne materials. Differences in the two systems include: temperature ranges — you have a much wider temperature range with the solvent-borne materials; and product odor is another issue — as the solvent evaporates there is a temporary odor associated with the evaporation. Solvents may also have a tendency to absorb a little deeper because the molecular size of the solvent is normally a little smaller than that of water, although this is not necessarily true 100 percent of the time. In making your product decision you need to weigh the differences between the two carriers. What temperature ranges do you have? What kind of results are you trying to achieve? What are the VOC (volatile organic compounds) laws in the given municipality?
"We have found in laboratory testing, for all practical purposes, the same type of results in both the water-borne and solvent-born systems." In summary, Wallace says, "The application of a quality water repellent is part of a sound and effective water management system. There are some redundancies there and the redundancies are there because we know we don't live in utopia. We know that designers don't always understand about through-wall flashing, weep holes and the proper use of control joints, and we also know that sometimes the mason contractors don't have the same quality of work on a Monday morning as he might on a Friday afternoon. Those things do happen in the real world. Water repellents may not be necessary to prevent water intrusion if everything is done correctly, just like we don't necessarily need to take multi-vitamins every day if we eat correctly. How many of us always eat correctly? Thus the importance of preventative measures.
"We understand the real world applications. We also understand that, in a utopian world, redundancy of materials may not be required, but in reality there is a place for a quality water repellent on most masonry structures and substrates."
About the Author
Jennie Farnsworth is an Atlanta-based freelance writer and editor. She is a former editor of Masonry magazine.