Maintenance and Repairs

July 12, 2024 Published by Golden Horseshoe Chapter - By Ben Martin

TTW Brick Masonry: What It Is, and Why We Should Care

From the Volume 20, Summer 2024 issue of the CCI GHC Condo News Magazine

While most of the brick masonry we see on buildings today is drained veneer used as part of rain screen wall assemblies, not so long ago the construction industry in Ontario, particularly southwestern Ontario, used a type of structural brick masonry known as Through-The-Wall (TTW) brick masonry as a way to allow for more rapid construction of multiunit residential buildings at lower costs. While no longer in use, this method of construction was something that began in the 1960’s and continued into the early 1990’s. Many of these buildings are still around and some are in fact condominium buildings. If you live in or manage one of these buildings, you may already be familiar with TTW brick. So what is it exactly?

Well, to answer that question, let’s first look at how brick masonry is typically utilized in present day construction. Typically, brick masonry is used as the outer most cladding layer in a drained rain-screen wall assembly, where the bricks are meant to stop bulk water from entering the wall system. Inevitably a little bit still gets through, either through cracked mortar joints, or simply by saturating the bricks to the point that it soaks through to the back side. This water then runs down inside the cavity between the brick veneer and the back-up structural wall component, and out through weep holes between bricks at the bottom of the wall. The brick veneer assembly is laterally tied to the back-up wall to keep it stable. There is a little more to it than that, but the point is that the bricks are only the first line of defense against leakage, and they are not a structural component of the wall assembly.

TTW brick is a different animal. A typical TTW brick wall assembly consists of a single wythe (row) of brick masonry with a cementitious parging layer covering the backside of the bricks. Often a layer of expanded polystyrene insulation is embedded in, or adhered to, the parging layer and then covered with drywall or plaster. Another variation includes light gauge steel stud framing and batt insulation instead of the layer of polystyrene insulation. That’s the whole wall system, if you can believe it!

The bricks are what holds the building up. The bricks are what keeps the water out. The bricks are what keeps the wind out…There is no secondary barrier against leakage. This makes maintaining the integrity of these bricks extremely important.

The challenge with bricks is that they soak up water like rigid sponges. This would be less of a problem if we lived in a much warmer climate where temperatures rarely, if ever, dropped below freezing, but here in the heart of southwestern Ontario, freezing temperatures are pretty common for nearly half of the calendar year. We’ve all seen what happens when water freezes and turns to ice - it expands. The same thing happens to water that has soaked into brick masonry, and when it expands, it starts to break apart the bricks from the inside out, causing the faces of the bricks to break away and fall off. The technical term for this deterioration is spalling. As more and more of the brick face breaks away, more water is absorbed by the wall assembly, leading to more spalling, and the cycle of progressive deterioration continues. This deterioration mechanism is common with all masonry, but its impact is more substantial with a TTW brick wall assembly because of the many functions these bricks are meant to perform within a wall assembly.

Repairing TTW brick is also a bit of a challenge, in no small part because replacement bricks are no longer manufactured in Canada and are usually not possible to source.

The other significant challenge with locally replacing TTW bricks is that we don’t want to damage the parging layer on the backside of the bricks, which would inevitably occur if entire bricks were removed. To avoid damage to the parging layer, typically only the front ½ - 2/3 of the brick is removed to avoid disturbing the parging. This requires a bit of skill and care on the part of the individual completing the removals.

Since replacement TTW bricks are typically not available, repairs are often carried out by using smaller brick pieces cut from regular size bricks. Since TTW brick masonry is structural, if more than a few bricks are being replaced in one area, shoring or temporary support for the remaining masonry may be required. Repairs can also be completed using concrete repair materials, although tend to stand out visually.

So what can be done to prevent this type of deterioration from occurring in the first place? Well, since the damage is caused when water absorbed by the masonry freezes, we either need to keep the bricks warm, keep the bricks dry, or both. Since the bricks are the outer most layer of a wall assembly and exposed to the elements, keeping the bricks warm in our climate is pretty hard to do.

There are a few more options available for keeping the bricks dry. Breathable sealers and coatings are available which are meant to keep bulk moisture from being absorbed by the bricks while also allowing any moisture within the bricks to evaporate to the exterior. While the life expectancy of coatings can vary, periodic recoating is required in order to maintain the integrity of the coating. Over-cladding is another option available which can be used to keep the bricks dry. Various forms of cladding are available, but the more commons systems would be prefinished steel or an exterior insulation and finish system (EIFS). These systems are a more long-term solution, but do come at a higher initial cost compared to sealers and coatings. One of the significant benefits of over-cladding is that it affords the opportunity to include insulation behind the cladding, which effectively keeps the bricks warm as well, with the added benefit of improved interior comfort and energy efficiency. In some cases, if deterioration is concentrated in specific areas, consideration could be given to only cladding the affected portions of the building.

In some cases water shedding flashings can be installed to help direct water away from the masonry, particularly at locations such as window sills and where balconies and walls meet.

Regardless of the approach taken, any deteriorated masonry should be repaired or replaced prior to over-cladding or coating application.

While localized repairs can often be carried out on a periodic basis to maintain the condition of the masonry, it is usually prudent to begin planning for eventual over-cladding or coating application as part of regular reserve fund planning so that funds are available when the time comes to undertake a significant project as this.

Ben Martin is a Construction Supervisor at Brown & Beattie Ltd., a building science engineering firm dedicated to providing clear and sensible building improvement, maintenance, and repair planning advice by listening to clients’ objectives. Ben is Professional Engineer and a University of Waterloo graduate with over 18 years of engineering and project management experience, primarily providing services to the private condominium sector.