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Seriously, You Couldn't Call First?


By David Leslie, RWC, Polyguard Architectural Division

In the world of roofing and waterproofing, rarely does a day go by when a colleague or client doesn’t utter the dreaded phrase, “So I have this situation …” I feel a pit forming in my stomach when I hear those words, because they’re typically said long after a painless solution to the problem is possible. After 30 years in the weather-barrier industry as an installer, consultant and manufacturer, I have been involved in countless “situation” conversations and can assure you they’re no fun. Let me offer an example.

My team has a project right now that has Underseal pre-applied, below-grade waterproofing on the foundation wall of a parking garage that will be tying into the podium deck waterproofing. In this case, the “situation” occurred after the concrete contractor had finished placing curbing around the podium deck (Fig. 1).

Fig. 1. Who is to blame for this?

The purpose of pre-applied waterproofing is to maximize efficiency by casting the concrete wall against it, eliminating the wasted space of a trench. The membrane from the top of the shoring wall down (which was never intended to see the light of day) is sandwiched between the concrete wall and the surrounding shoring wall. A flap of excess membrane of the pre-applied waterproofing must be left exposed above the shoring wall in the transition area and remain viable so it can be tied into the podium waterproofing at a later time. That requirement was ignored. 

Instead, the transition strip used to connect the two systems was removed. How could qualified contractors do this? 

The primary reason is that only a handful of people really understand why that flap of random membrane is so important. In this case, the concrete contractor didn’t understand that the flap was a critical connector for the two different systems. Because the overarching goal was to just get the work done, the concrete crew cut the membrane off at the top of the shoring wall and wadded up the vertical leg into the corner of the form, making it completely unusable. 

It is at critical junctions like this — better known as terminations, transitions and penetrations — that 90 percent of all water intrusion has been documented to occur. Considering the different contractors working on a project and the various connections between systems, it is easy to see why most leaks happen at these junctions.

What is the fix for a situation like this one? Unfortunately, the correction is often demanding and sometimes completely unreasonable to perform. We see it every day: Major grade beams cast without waterproofing, large banks of utility lines running through the waterproofing without being detailed. Truly, the only way to properly correct those missteps is to jack out the concrete and start over. But rarely can a project absorb the additional cost or delayed schedule to make such extensive corrections.

In the pictured example, the fill under the podium deck must be excavated, exposing the membrane to install a transition membrane. Making this correction after the fact adds time and expensive that could have been avoided.

Who’s job is it to prevent this type of situation? While it’s everyone’s responsibility, the general contractor must take ownership. The problem is that the modern-day construction method of design-bid-build is fragmented. All the participants are specialists focusing on a single task, unaware of how their work impacts the building as a whole. In fact, the contract documents intentionally silo the individual disciplines and then isolate the lines of communication. The general contractor is obligated to the owner to produce a building that meets the contractual agreement. Ultimately, coordination between the various trades as well as verification that the project outlined in contract documents is constructible are both the responsibility of the general contractor.   

One would say, therefore, that the general contractor, in the situation described, should have done a better job, but the issue is not that clear cut. A general contractor who makes weathertight buildings cannot personally monitor every inch of a project. One person — an architect, a foreman or a consultant — is typically made responsible for critical systems, such as HVAC, structural and building envelope. That individual’s most important attribute is knowing what problems to anticipate before they happen. By being aware of junctions prone to leaks and water damage, he or she can direct questions and concerns in advance to the correct advisers.     

It is hard to fathom how new buildings can leak when the primary purpose of a building is to provide shelter from outside elements. While there are actually many reasons a new building leaks, there are no good reasons. And sadly, the number-one cause of litigation in new construction is water intrusion.

To avoid the "situation" conversation, consult the experts when it comes to terminations, transitions, and penetrations during construction. This will help keep you on schedule, on budget and out of court.

*Claims or positions expressed by sponsoring authors do not necessarily reflect the views of TPC, Durability + Design or its editors.

David Leslie, RWC, Polyguard Architectural Division

David Leslie is director of technical services at Polyguard. For nearly 30 years, he has been involved with every aspect of the roofing and waterproofing businesses, including building envelope consulting (new construction and remediation projects), the development and manufacturing of weather barrier systems, and as project superintendent of the installation for major roofing and waterproofing projects nationwide.



Tagged categories: Good Technical Practice; water leakage; Waterproofing


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