The Economics of Quality Assurance in Waterproofing: Asteroids, Banana Peels, and Your Bank Account
- John D'Annunzio
- Aug 2, 2018
- 6 min read
A quality assurance program identifies the requirements of the completed waterproofing project, sets the quality levels required for project approval, and determines a chain of custody to ensure those levels are tested and validated.
Quality assurance can be implemented at every phase in the waterproofing construction process. Waterproofing quality assurance is one of the cheapest insurance policies you can buy. And having a quality assurance inspector on your project can actually help the project move forward more smoothly.
At the design phase, quality assurance can ensure that the design meets the code requirements and that the materials specified can are accurate for the site-specific conditions. Review of site testing – i.e. soil conditions, water table level, presence of hydrostatic pressure, chemicals – have an impact on the type of materials required. Having a qualified waterproofing expert review the initial project design documents can provide cost savings by eliminating delays in construction from change orders and potential material failures.
"The waterproofing system is one of the few major building components for which, once completed, there is no immediate access for repairs. If a leak occurs on a waterproofing project, the cost of excavation and/or coverings could exceed the cost of the initial application."
At the waterproofing application phase quality assurance is monitored by an on-site quality control inspector. The role of the quality control inspector is to verify that the work and materials used satisfy the applicable standards as specified within the quality assurance process. They are your "sheriff" on the project. The quality control process may also include on-site testing to ensure application is in accordance with the project requirements. The quality control inspector can also serve as a liaison between the Owner and the project participants – Designer, Project Manager, Applicators – and serve as part of the team that approves modifications to design, materials, and application methods as on-site conditions arise.
The primary reason for the use of quality assurance on your next waterproofing project is risk v. cost. Risk can be broken into probabilistic risk and inherent risk. Inherent risk describes the level of catastrophe if something does go wrong, whereas probabilistic risk implies the likelihood of something going wrong. When analyzing the risk of an asteroid, we would say the probabilistic risk is low but the inherent risk is high. Stepping on a banana peel and dying? Inherent = low, probabilistic? You guessed it (and watch your step, especially at the zoo!)
Water intrusion is a high inherent risk to your building. Quite literally, water can erode your building (not to mention erode your bank account). Water intrusion can crack, split, degrade, and render your building useless. Water can create mold and all manner of risk to your building and its contents.
But wait, that's not all. The waterproofing system is one of the few major building components for which, once completed, there is no immediate access for repairs. If a leak occurs on a waterproofing project, the cost of excavation and/or coverings could exceed the cost of the initial application. The reason for this is that in below-grade waterproofing the cost of excavation far exceeds the initial cost of application. For instance, an opening may be located deep below the surface requiring removal of overburden, such as trees, concrete, landscaping, followed by excavation of soil to reach the point of moisture infiltration. Once the repair is made everything must be put back.
So, not only is the inherent risk level high, but with waterproofing you only have one chance to do it right.
But the news isn't all bad. The good news is that probabilistic risk can be managed. In other words, you can take steps to waterproof properly.
Taking that into consideration, the quality assurance process can be viewed as an insurance policy. The cost of quality assurance may be less than the cost of excavation required to repair one leak. Most manufacturers warranties do not cover the cost of excavation. Studies indicate that projects that have quality assurance in place experience fewer call backs than projects without quality assurance.
In the past thirty years I have conducted evaluations on dozens of waterproofing failures. The causes of these failures ranged from improper design, improper material selection and improper workmanship. The most memorable failures were the instances where the waterproofing membrane was never applied prior to backfill. Imagine the look on the owner’s face when they are informed that the building is leaking because the waterproofing application that they paid for never occurred!
Although it is easy to diagnosis the problem, the resolution is extremely costly. One of the cases occurred at a runway of a major U.S. airport. The runway was applied over an underground structure that housed the computer terminal for the airport. The runway concrete – extremely thick – had to be removed, the waterproofing system had to be applied and the runway concrete – extremely thick – had to be repoured. This is an extreme case; however, it is not all that uncommon.
Waterproofing is applied in phases as construction of walls and plaza decks are installed. There may be extended periods of time between certain waterproofing applications and completion. For instance, waterproofing of below-grade walls is typically done in 6 to 8- foot increments from the bottom to the top. The initial section is finished, the site is backfilled, and the waterproofing applicator uses the backfill as a scaffolding to complete the next increment. This process is continued until the full wall is waterproofed. This process could continue over an extended period because the waterproofing applicator relies on the pour schedule and the backfilling process.
There have been instances where the backfill is applied prior to the completion of the membrane application. At least once a year I receive a call to investigate a waterproofing leak and the result is that membrane was not applied in a section that has been backfilled. If the owner is fortunate the area backfilled prematurely is the top lift and only minor excavation is required to apply the membrane.
I have also had a couple cases where the membrane was purposely not set in designated areas to accommodate future openings for wall equipment penetrations. When the wall equipment was installed it was found that the designated openings were too large so the actual cuts to the wall decreased in size. Unfortunately, no one alerted the waterproofing contractor, so the area was backfilled without the application of the waterproofing membrane at the perimeter of the opening.
The previously mentioned failures were the exception – most waterproofing failures occur where the membrane has been installed – albeit improperly. The most common cause of waterproofing failures is improper workmanship. To a large extent the problems can be traced to the changes in materials and application methods that we have experienced in the past decade. Most of materials used today have ambient temperature constraints that limit their use. If the material is applied when it is too hot or too cold or if they are not properly stored in warm areas prior to use, the chance of failure increases.
We now use a substantial amount of cold applied materials for membrane adhesion – the most important element of the waterproofing membrane application. If these materials are not applied at the manufacturer required coverage rates – too much or too little – the chance of failure increases. The chance of failure also increases if the adhesives do not cure – or cure too quickly – prior to membrane application.
The improper use of materials is also a concern. With the increase in popularity of ‘garden type’, ‘living’ or ‘green’ roof applications in the early 2000s, a significant number of roof system manufacturers began to identify their roof membranes as waterproofing membranes. These types of materials may be suited for some waterproofing applications – such as horizontal plaza decks – they are not suited for most other waterproofing applications. The reason for this is the conditions that waterproofing membranes are to perform under (literally) are vastly different than requirements for roofs.
So, whether it is materials, design, application, backfill, or seemingly random accidents (backhoes, etc!) there are many opportunities to get the waterproofing system wrong, but there are exactly zero opportunities afterward to go back and do it right. A quality assurance inspector, who represents your best interests, can help ensure it is done right the first time and save you millions of dollars, sleepless nights, lawsuits, and all manner of stress as a result.
Until next time,
John D'Annunzio
John D’Annunzio is one of the most respected voices and minds in the technical aspects of roof evaluation, roof design, and roof management. With over 25 years as a roofing consultant to Fortune 500 companies and a technical consultant to major architectural firms around the USA. He has served on projects around the world while writing four books on roofing and waterproofing, serving as an expert witness, and performing laboratory analysis of roofing materials. John is the Managing Editor for Architectural Roofing & Waterproofing Magazine and technical editor for Roofing Contractor Magazine.
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