Mark Meshulam is an expert witness and exterior facade consultant for window leaks in tall buildings.
As we head into our rainy season, there are many participants in a relatively recent social experiment – life in a high-rise – who will discover that their “building envelope” is not enveloping them as well as it did last season. Just like a bucket or a car tire, a building can spring a leak, too.

In a single family dwelling, a leak can be a smaller-scale affair. Get a ladder, call a local handyman, get a few tubes of caulk, and in many cases the leak can go away, at least for a while.

A larger building presents larger challenges, not the least of which is altitude. Since we haven’t evolved wings yet, and don’t appear to be getting this upgrade any time soon, we must surmount the hurdle of getting to the work area on the outside of the building with a skilled individual. This takes planning, effort, cost and a worker with cohones grande.

Many of our buildings are well over 20 stories – 200 feet. These don’t look scarily tall from the ground, but standing on the edge of the roof will instill a profound respect in even the most chutzpah-laden individual.

Thankfully, there are folks out there who are willing to suspend themselves from a rope, sitting on a little plywood board, and rapel down the side of the building. I work with these guys often. Just before they go over the side, I ask them if they like using the “bosun’s chair”. Two out of three say no.

Workman using bosun's chair to investigate leakage in tall building

The bosun’s chair operator has his hands full. One hand holds the rope coming out of the bottom of a friction device. His hand position either exerts more friction on the rope to slow his descent, or less friction to speed him up. His plywood seat is suspended from the friction device. His other hand operates a rope grab on a second rope – the safety rope. This rope grab slides up and down the safety rope. In order to be able to slide down, the workman must hold a lever on the rope grab in the up position. If he doesn’t hold the lever up, he can’t go down.

Now we get to the quandary. Two hands are both occupied with vertical travel. More hands are needed for work. And so, when lowered to his work position, the worker must tie off the friction device, let the rope grab hang with its own friction, and get to work.

Hanging suspended from essentially one rope makes it hard to remain stable when working. Think of the astronaut movies you have seen. If the astronaut wants to get anything done, he must brace or tie himself in position or else he might drift away with the force of his own actions. Our bosun chair man is in a similar position. If he needs to pry off a window part, he might find that he doesn’t have enough resistance to do it.

This is why many bosun’s chair operators carry along one or two suction cups, and they wire these to their harness to hold them steady. Glass, as every child knows, is the best thing ever for suction-cupping.

Workman looking for window leak in tall building from bosun's chair

Despite these challenges and limitations, the bosun’s chair remains the hands-down most economical way to get a quick glimpse at the exterior of the building, and even perform a minor repair. Larger repairs and projects call for suspended scaffolding that can accommodate 2-3 workers in a more comfortable standing position, with ample room for tools and materials.

Leak investigation in a tall building

Since it is so darned inconvenient to hang a man from the side of the building, there are important tasks that should be done first, in order to maximize the value of the “drop”. These include:

1. Understand the nature and frequency of the leak. Is it frequent or rare? Does it start immediately when it rains, or is there a delay? What wind direction brings the worst leakage? Where on the wall of the interior space does the leak present itself? Is it always at the top of the window? Always at the bottom?

Is there a pattern of leakage in the building? It is at a particularly difficult transition in the building’s facade? Is there evidence of water traveling from one unit down into the one below?

2. Gathering all of these answers will result in the emergence of a picture of the problem in much the same way a physician builds a picture of your health by listening to your heart, weighing you, and fondling your private parts. Now it’s time to gather a new kind of data: how is the building constructed?

3. Reviewing the “As Built” architectural or structural drawings will yield a wealth of information which can serve as clues to why the leak is happening. This should lead you to the point of developing some theories about what is going on.

Use architectural drawings to track down building leaks

5. When the workman is suspended in mid-air, it will be important to be able to communicate with him during his entire descent. Cell phones and radios come in very handy. You will see that in the video that accompanies this article, I was able to lower my video camera from cords, and see the work area myself. When the workman is in a position to make observations, he can then confer with others who can collaboratively make the call about what to do.

6. If the workman finds something that could be a likely source of the leak, it is good that he try to fix it, even if that fix might not be the final remedy. First, this can reduce the building’s exposure to further damage. Second, the results of that fix can be a clue to whether that type of fix is helpful, hurtful or benign. How can a fix be hurtful? If it blocks a drainage path and causes water to build up inside the wall. Drainage paths must be understood before turning loose our suspended savior.

7. If these quick window repairs are not effective, or if a window leak is prevalent, as opposed to a one-off, it is time for field testing of the windows or curtainwalls. Field testing is the selective application of water to portions of the exterior of the windows while observing the result from the inside. There are numerous procedures for field testing windows and curtainwalls, and they must be selected by an exterior facade consultant or window testing expert for maximum effectiveness. If you need help with field testing of windows, glass or curtainwalls, call me.

Mark Meshulam, Chicago Window Expert will stop your building leak or his name isn't Mark Meshulam, Chicago Window Expert