THE PROBLEM

Leaks at this four story office building at the locations indicated in Figure 1 are the result of a couple of conditions. The first condition is the obvious one, which is cracked mortar joints and broken brick in the single wythe wall. The other condition is hidden.

Fig.2 below shows the state of the wall on the outside at one of the leak locations. Fig. 3 is on the inside of that wall during a wind driven rain.

In a properly built single wythe wall water on the inside of the brick (such as it is in Fig. 3.) will flow to weeps at the base of the brick panel and from there back to the outside. Unfortunately, the walls that are the source of the leaks were not properly built. That is the hidden problem.

The proper arrangement is as shown in Figures 4 and 5. Here, a cavity exists between the vertical leg of the shelf angle and the back of the brick. Cracked brick and broken mortar joints are leak paths but even sound brick and solid mortar joints are not waterproof. Under certain conditions brick walls become saturated so the space is there as a path for water to escape.

Figures 6 and 7 are pictures of the wall above the ceiling on one of the upper floors. Note that the black, polyethylene vapor barrier is in contact with the brick shelf angle. There is no space between the vertical leg of the brick shelf angle and the brick as there is in Figures 4 and 5. With the wall as it is, cracked and built without the cavity behind the brick, and also without flashing, the water that penetrates the brick or the mortar joints flows down the plastic vapor barrier until it reaches the elevation at which the plastic is in contact with the top of the shelf angle. Some of that water will flow to the bottom course of brick and out the weeps. During heavy, wind blown rain the amount of water exceeds that which can flow through the confined space behind the brick. The excess water gets out somewhere else and flows to the inside.

THE REMEDY

It’s possible of course to remove the improperly placed brick and replace it with brick courses in the right location on the brick shelf. Although possible, this remedy is impratical. Fortunately it is also probably not necessary.

According to the building engineer and some of the tenants the leaks that have occured in the past couple of years have only been during hard rains accompanied by strong winds that produce a significant pressure differential between the exterior surface and the interior spaces. Those conditions existed when the picture in Fig.2 was taken. That image shows a soaked mortar joint. The brick isn’t saturated. This is a clear indiction that the leak is in the joint and not due to saturation of the brick. Since it can be seen from the outside that many of the mortar joints are broken its likely, if not certain, that repairing these joints and replacing the broken brick will significantly reduce the leaks.

Although the construction error will still exist it may not result in water making its way to the interior if there are no cracks. Without cracked brick and mortar joints the only moisture that will form or accumulate on the back of the brick will be due to condensation or saturation, neither of which appear to be significant.

We therefore recommend that a brick replacement and tuckpointing project be undertaken in which only the broken brick be replaced and the failed mortar joints repaired. We would be glad to provide a Scope of Work and Specifications for that project and provide other assistance and services before and during the project execution to see it through.