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

Recreational climbers are doing it for the joy and the challenge. Their sole activity is safe propulsion up or down a big rock. Our bosun’s chair operators, on the other hand, must hang like monkeys on the side of a building for hours on end, because it puts food on the table, and while hanging there, they must actually get things done. It’s that “working thing” that sucks the joy out of a lot of activities that could be otherwise pleasurable.

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

Ok, we are ready to work now – where are the tools? As if the poor guy didn’t have enough to be concerned with, he must also carry with him every tool and material he might need during the vertical journey. Usually this is carried in a bucket that is also tied to our trusty daredevil.

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
Use architectural drawings to track down building leaks

4. Now it’s time to instruct the worker, while he is still on solid ground. He will need to be oriented regarding how the building is built, and sensitized to potential trouble spots. In short, he needs to know what he is looking for. With this planning, he can then be prepared with tools and materials that might be needed while on the side of the building.

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

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5 thoughts on “Fixing Window Leaks in Tall Buildings”

  1. Mark,

    Greetings. I work with safety at Edwards AFB, CA. We routinely have 15-20 MPH winds. I have not been able to find a regulation that prescribes wind limitations for bosun chair operations. Would you happen to know a good reference to the Code Of Federal Regulations? Thanks in advance.


    Jimmy Otero

    JT3 Safety

    No Safety, Know Pain

    Know Safety, No Pain

  2. Hi Jimmy,
    The State of California has issued these standards, but they do not cover wind speed:

    Department of Industrial Relations
    Subchapter 7. General Industry Safety Orders
    Group 1. General Physical Conditions and Structures Orders
    Article 5. Window Cleaning

    Another safety resource for Bosun (Boatswain) chair use is here:

    North Carolina Department of Labor

    The definitive word is from OSHA:
    A Guide to Scaffold Use in the Construction Industry

    Here is the little that is said regarding weather:
    (8) Employees shall be prohibited from working
    on scaffolds covered with snow, ice, or other
    slippery material except as necessary for removal of
    such materials.
    (12) Work on or from scaffolds is prohibited
    during storms or high winds unless a competent
    person has determined that it is safe for employees
    to be on the scaffold and those employees are
    protected by a personal fall arrest system or wind
    screens. Wind screens shall not be used unless the
    scaffold is secured against the anticipated wind
    forces imposed.
    This may be the only time I have seen an example of under-regulation!

  3. Mark,

    Good morning. I hope the “freakish” snow storm hasn’t impacted you too bad. Thank you for such a swift reply. I totally agree with you about the under regulating. Edwards AFB is in the Mojave Desert. The typical weather forecast calls for winds to be variable, 5-5 MPH with 25 MPH gusts (5-20 MPH winds are considered normal, but “an unpleasant part of the desert”). Folks here don’t get concerned unless winds reach or gust 50 MPH (about 15% of the year). I am authorized by OSHA to teach 10-Hr and 30-Hr (OSHA 500). However, wind strengths are never discussed, nor have I heard them discussed. I heard that there is an ANSI standard that covers wind, but until I see it, I’m treating that as a rumor only.

    I once stopped a window washing operation due to what I perceived was too strong winds (by referencing a nearby wind sock). This was at the Los Angeles Unified School District headquarters (I was the safety director there). I took a lot of heat initially, but once everybody cooled down, we contacted the mobile scaffold manufacturer (probably our only authority for any operation). The wind sock indicated 20 MPH, the manufacturer said they restrict ops at 14 MPH.

    As far as a competent person goes, I sure wouldn’t sign a statement claiming that operations in the winds were safe. The fact is, we have tower climbing, craning, scaffold, and other forms of high work that would also be affected by winds. Thanks again for your insight. It’s always good to hear from informed people.

    Best regards,

    Jimmy Otero

  4. Hi! I’ve been reading your site for a long time now and finally got the bravery to go ahead and give you a shout out from Lubbock Tx! Just wanted to tell you keep up the great job!

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