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Sealing Leaking Mechanical Equipment
A Specific Case One such specific instance of leaking roof top equipment involved a large Home Improvement Supply House. We received a call that their roof was leaking and that numerous attempts had been made to correct it....all in vain. The leak was active for well over a year bringing the manager to his wits end. Upon visiting the store, and knowing this was a long term problem we insisted on seeing the leak from the inside, up close, and during a hard rain. A large stepladder was brought in to access the underside of the roof. Our inspection indicated the leak was originating from an area higher than the roof. Simply put – we saw water dripping from inside of an equipment curb which is at least a foot higher than the roof surface elevation. From this we knew the leak was coming from the mechanical equipment and not the roof system. Whenever tracking these kinds of leaks it’s always best to see them when they’re active. That helps greatly in identifying their true point of entry and what it might be on the roof which is defective. So again, from our interior inspection we believed the leak was coming from inside of the equipment curbing. As you follow the pictures you’ll see what we found. This happens far more than you’d expect. In this case we were able to locate the leak without a systematic water test, but in some cases such a test is the best solution.
What's Wrong With This Picture? (NOTE: The "Arrows" mentioned below can be found in this picture of a rooftop equipment installation. CLICK IMAGE TO ENLARGE.) 
To further give you some idea of what can go wrong with mechanical equipment lets take a closer look at installation techniques. We submit this picture for your study because there isn’t much else which can be done wrong here! This is a perfect example of how 80% of all roof leaks are related to roof penetrations (areas where the field of the roof is interrupted and penetrated). Mechanical contractors who routinely create roof penetrations while installing rooftop equipment may not understand basic roofing principals.
Many landlords make the mistake of allowing much too ‘easy access’ of their roof surfaces. Mechanical contractors who are not at all familiar with what a roof can and can’t endure routinely abuse roof systems without even recognizing it. Others, with less concern, are capable of serious damage. Roofs are not intended to have heavy mechanical equipment dragged over top of them, or sheet metal cowlings dropped on them, or screw fasteners stepped into them, or conduit lines fastened through them, or....well you get the idea.
Do you know who’s installing your equipment, and whether or not they understand how to ‘respect’ your roof? Most of our commercial clients insist that any mechanical fit out work, done on any of their buildings (by any of their tenants) be done in coordination with Cooper Roofing Corporation. They know we will represent their best interest when those not completely familiar with roof system ‘etiquette’ begin traversing and cutting their roof. Arrow 1 shows the lag bolt which is screwed through the 4 x 4 wood support into the roof. NEVER fasten through a roof like this. NEVER puncture a waterproof roofing system unless you know what you’re doing and have made proper provisions to compensate for this sort of puncture. In this application over time the bolt(s) will absolutely cause leaks as the wood deteriorates from swelling and shrinking due to water absorption. Arrow 2 shows the attempt to seal the wood supports to the roof surface with asphalt roof cement. This is intended to keep water from getting under the wood where the lag bolts have punctured the roof. Because of the vibration this unit creates, and through normal deterioration of the wood supports, the wood will move and crack the roof cement. Aside from these movement problems, roof cement is not able to seal to a porous material like wood. Wood will ‘soak up’ water when it gets wet (like a sponge to some degree) and the roof cement will lose it’s adhesion to the surface of the wood. Eventually peeling will result (if you look close you can see it already starting to happen). Arrow 3 shows one of the most common mistakes we see regarding pitch pocket installation. This is called ‘bundling’. Notice that the conduit, refrigerant lines and control lines are all wrapped together and bundled with tape. This may look efficient but is a major cause of leaks. If you look at where this arrow is pointing you’ll start to understand. Water can easily follow the center of these bundled lines into the building. In other words each line MUST be individually sealed where it penetrates through the roof or water will follow the bundle (where they aren’t sealed) into the building. That bundle may look tight but we guarantee you water will follow it into the building unless each and every line is separated and encased in sealant. Arrow 4 shows more roof cement applied on this ‘shingle vent pipe collar’. Trying to keep this tight with roof cement is not going to happen. Keep in mind roof cement cures hard with very little elasticity. This connection will be cracking from the brittle roof cement not being able to withstand unit line vibration. There are much better elastomeric products to use inside of pitch pockets these days. Arrow 5 simply points out that this is, as mentioned earlier, a shingle vent collar- NOT something to use in this flat roof application. This is an aluminum flashing made for use on a shingle roof where plumbing vent pipes rise up through the shingle roof. It is not intended to be used on a flat roof as a pitch pocket. Arrow 6 shows even more roof cement used to seal the flange of the aluminum shingle vent collar to the asphalt roof. No reinforcing fabric was used which helps dissimilar materials (like aluminum and asphalt) from splitting and cracking apart. Not that reinforcing fabric would’ve made a big difference within this misapplication. We’re just pointing out the utter lack of roofing understanding at play here. Arrow 7 points out a mechanical pipe, which was part of this installation, being sealed to the roof with what else but.....roof cement. The shear height of this pipe dictates it will be moving in the wind, not to mention inherent thermal expansion/contraction of the steel. There’s no way roof cement will withstand this sort of severe environment. Arrow 8 is there to show the placement location of this unit. Only an experienced eye can tell in this picture that the unit is sitting in the path of the roof drainage line. Water will pass over this conglomeration of mistakes in large amounts as it is channeled to the drain in this area. Not good considering the problems just reviewed. This was not intended to ridicule mechanical contractors and their efforts at roofing. Some are conscientious and knowledgeable with regards to roofing... but many are not. This critique is intended to warn you, the customer, of what can happen when you decide to have heating, air conditioning or any other kind of climate control or food refrigeration equipment installed on your roof. Don’t assume all mechanical contractors are roof savvy, and for that matter, the same can be said of roofing contractors. Do your homework. Ask around and be confident in your contractor before allowing someone to cut open and penetrate your roof. Contact Cooper Roofing Corporation to review the many ways we can help you safely get through your next rooftop mechanical fit out alteration. Cooper Roofing Corporation - 610.275.7663 (ROOF) |
