A detailed discussion of subgrade waterproofing was at the forefront when Paul Beers invited David Gehlbach to the “Everything Building Envelope” podcast.
David Gehlbach’s background as a licensed architect contributes to his comprehensive understanding of subgrade waterproofing and the construction process. In his position as sales manager for the building products division at CETCO, David Gehlbach has witnessed firsthand the costs that accrue when the importance of this vital part of construction is overlooked.
With that experience behind him, David has both cautionary tales and strategies for success to share with the “Everything Building Envelope” audience.
What Lies Beneath
Underground facilities, such as parking garages, help expand the use of space — and that’s a necessity when land is at a premium. But maximizing the potential of the property by going underground comes with increased responsibility for subgrade waterproofing and calls for the development of another skillset. Below grade structures need to be protected from moisture infiltration, but there isn’t a one-size-fits all solution for keeping the structure dry.
Numerous factors need to be assessed to prepare the waterproofing plan, including physical considerations, such as hydrostatic conditions and salt content, as well as the owner’s plans for the building and the type of guarantee that’s desired.
Most waterproofing conditions can be addressed with bentonite and polymer products, with different levels in the product lines that suit various conditions.
Bentonite is a natural clay that expands when it comes into contact with moisture. Sheets are applied to the below-grade concrete wall, either before or after concrete is poured. When it gets wet, it expands and seals any voids. The sheets have to be under compaction, either from the earth or a topping slab.
For sites with elevated levels of salt or contamination, a saltwater-grade of bentonite may be used, or one might switch to a polymer product when the saltwater content is very high.
When the Budget Fails
Moisture infiltration, mold and health hazards arising from problems with subgrade waterproofing lead to expensive legal settlements and rebuild solutions. Yet waterproofing costs are a small part of the construction budget when executed properly and in the correct sequence.
Waterproofing problems often begin before construction, when waterproofing costs are underestimated. The atmosphere around the perceived overrun can lead to regrettable decisions about avoiding items that were specified in response to site conditions or even, in some cases, omitting waterproofing entirely.
Budget miscalculations can be avoided by bringing waterproofing specialists into the planning stage. This approach is taken as part of due diligence for other elements of the building, such as glazing, but isn’t yet routine for waterproofing.
In David Gehlbach’s experience, most leaks in waterproofing are due to “rogue” penetrations in the wall from other building activities that were overlooked, such as installing pipes or electrical work, rather than product failure, pointing to a need for communication between the project team. That experience also highlights the need to understand how each component of the construction interacts with the subgrade waterproofing, as one material transitions to another.
David Gehlbach notes that CETCO offers a hydrashield quality assurance program, which guarantees that the company will fix any leaks to the building — no questions asked — with injection technology from the interior of the building.
To be eligible for that warranty, the owner needs to comply with a few conditions set by CETCO. Those conditions include hiring a certified inspector and a waterproofing consultant approved by CETCO, who inspects the installation and backfill throughout the process. There needs to be an approved applicator who is part of the hydrashield warranty program. There is also a mandatory pre-construction meeting and constant communication between the field services unit during the waterproofing process.
Hear the complete discussion between Paul Beers and David Gehlbach at the “Everything Building Envelope” website, and don’t forget to subscribe while you’re there. You won’t want to miss any future discussions with industry professionals.