How Do I Waterproof an Elevator Pit?

We get a lot of questions about how you waterproof an elevator pit, so our Canada technical representative Gary Tench, the ‘elevator pit whisperer,’ thought it was time to write an article about best practices. Here’s what Gary had to say:

There are two methods for waterproofing an elevator pit: from the outside, or from the inside. Waterproofing from the outside, also known as positive-side waterproofing, is the best method for protecting the concrete, the steel, and also the interior space. When you waterproof your elevator pits during pre-construction, you get the maximum performance out of your waterproofing system when you use the proper application procedures. The caveat to this is that your waterproofing contractors must follow the strict application protocols to the letter.

The second scenario is waterproofing your elevator pits from the inside, also known as negative-side waterproofing. Depending on the project, this can be new construction, or it can be performed as part of a restoration project. You’d be surprised (or maybe not?) by the number of calls we get from multi-story building maintenance managers. They are often the unlucky people left holding the bag because they’ve inherited a history of bad waterproofing prevention and protection in their elevator pits.

You see, most people think it’s appropriate to just cover the elevator pit walls in some sort of non-breathable coating to “waterproof” them, unaware that these types of coatings trap the moisture causing them to bubble and flake off the concrete surface, leaving their elevators with no real protection.  The intruding hydrostatic pressure surrounding the structure continues pushing through until they have a small leak, which then becomes a much bigger leak that can be very costly to address, not to mention a public relations issue with the building’s occupants.

The unsuspecting maintenance manager comes to work one morning to find two feet of water in the bottom of the elevator pit. As a result, they have to shut down the elevators, try to remove this water, which can be sometimes very tricky, and then address the cause of the leak.  At the same time, they’re also dealing with angry tenants.

By the time they call us, they’re in a panic.

Here’s the good news: there is a cost-effective way to prevent this situation altogether, which I will explain in a moment, but first, let’s talk about the steps you take to waterproof your elevator pit from the interior.  Here’s what you will need to do:

• Shut the elevators down.
• Identify where the leaks are coming from. This is critical. The leaks could have been there for years and as we know, water always finds the pathway of least resistance.  Cracks, joints, and poorly consolidated concrete are the ‘usual suspects’ for water infiltration.
• Pumping the water out of your elevator pit can be very tricky. The factors determining your best water removal protocol will depend on where it is. If you’re in a dense urban area, it can be logistically tricky. You may have local municipal requirements, and the depth of your elevator pit will also factor into your water-removal solution. Regardless, this water must be removed.
• Once you’ve pumped out the water, you’ll want to bring in several industrial fans to dry out your elevator pit. It’s a nuisance getting them into the elevator pit, but it has to be done. The area needs to be dried out.
• Prior to selecting your waterproofing material, it is essential for you to determine if there is an admixture or any other type of material on or within the concrete that could be disruptive to your repair, or could repel the coating I’m about to recommend you use. Hopefully, you can find access this information from the original engineer, contractor, or building owner. If not, then there are methods–such as core sampling–that can help you determine this. If so, we’ll need the results of that core sample to identify your best alternative solution.
• Next, inspect the concrete to determine what needs to be done to repair it. Are there cracks? Is the concrete deteriorated to the level of exposing the reinforcing steel? It is critical that all of these areas are repaired. If there are active leaks, methods to address these include urethane injection, or possibly a hydraulic cement, both designed to stop the flow of water. A hydraulic cement reacts to the water and heats up, allowing it to cure. This is very effective for your active water leak scenarios. If this is not feasible, then urethane crack injection is an effective–and fairly costly–method.
• There are also patching and repair mortars. These types of waterproofing materials can be mixed just with water and applied without a lot of training; however, this can be somewhat risky, because, without a full understanding of waterproofing techniques and materials, the repair may not be as effective, leaving you back at square one. (In a perfect world, there are no issues with your concrete surface repelling water, and once all the surface preparation and repairs are complete, the material can be applied fairly easily.)
• It’s difficult to get a power sprayer into a confined space like an elevator pit, so you may have to mechanically grind the concrete surface to open up the pores. If there’s a little moisture on the surface, that’s okay – you want it SSD, or, saturated, surface dry – where it’s not wet on the surface, but it’s moist. That moisture within the concrete aids in the bond and penetration of the waterproofing material into the pores.
• Once you’ve applied the waterproofing material, it is critical to protect the surface from drying. You’ll need to keep that surface moist for 72 hours to fully cure the waterproofing material.

What I just described was a typical scenario. However, if your elevator pit is contaminated in some way–from chemicals or hydraulic fluids–an alternative method of protection would be required, but this scenario is uncommon.

Prevention is Worth a Ton of R.O.I.

I recommend to all building engineers, maintenance managers, and owners that they spend the extra money on the front end to just waterproof their elevator pits with a premium product with no-VOCs (volatile organic compounds). Financially, they will still come out ahead. Using this type of material will prevent the yearly hassle, labor, and non-breathable coating costs, not to mention the even costlier hassle of elevator leaks in an emergency situation, which can also result in your building owner losing valuable, steady paying building tenants.

Our GEMITE waterproofing products can survive for decades of service when applied correctly. I challenge anyone to run a cost analysis on annual reinspection and treatment vs. coating their elevator pit on the front end. You’re eliminating the annual upkeep expenses allotted for yearly maintenance, plus the costs and downtime associated with a major repair.

If you have any questions about waterproofing elevator pits, please contact Christian Warren, United States based, at cwarren@wrmeadows.com or Gary Tench, Canadian based, at gmtench@wrmeadows.com. Alternatively, you can call (800) 342-5976.

Below please find our comparable list of products to those mentioned in this article:

• Hydraulic Cement = MEADOW-PLUG
• Crystalline Waterproofing = CEM-KOTE CW PLUS
• Flexible Cementitious Coating = CEM-KOTE FLEX ST
• Chemical-Resistant Flexible Cementitious Coating = CEM-KOTE FLEX CR
• Patching and Repair Mortars: W. R. MEADOWS Patching & Repair Mortar Options

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