Water in the Elevator Pit Is a Building Envelope Problem

The call comes in as an elevator problem. There is water in the pit, the elevator contractor has been out, they pumped it, and it is back.

It will keep coming back, because the elevator has nothing to do with it.

The pit is simply the lowest point in the building. Water that gets past the below-grade waterproofing anywhere across the parkade level travels through and along the structure until it reaches somewhere it can collect, and that is the pit. It is functioning as a sump regardless of whether anyone designed it as one.

Why the lowest point tells you the most

An elevator pit is a useful diagnostic feature precisely because it collects. Water entering a below-grade wall thirty metres away does not announce itself at the wall. It moves through the structure, along construction joints, around service penetrations, and under the slab, and it arrives where gravity takes it.

That means the pit gives you an early and reliable signal that below-grade waterproofing is being overcome somewhere, well before that same water produces visible damage in the parkade itself. Buildings that pump the pit and move on are discarding the one instrument they have.

The corollary is that the pit almost never marks the entry point. Finding where water is actually crossing the structure is a separate investigation, and the approaches available are set out in the guide on moisture testing methods.

Groundwater or plumbing

Before any repair is scoped, this question has to be settled, because the two answers lead to completely different work.

Groundwater follows the season. In Metro Vancouver the water table rises through the wet months and falls through late summer. A pit that is dry in August, damp by late October, and holding water from November through April is tracking the table. Sites near the water in Vancouver, across much of Richmond, and in low-lying parts of Burnaby and New Westminster are especially prone to this, and site conditions govern far more than building age does.

Plumbing and drainage sources behave differently. They run at a more constant rate through the year, they may correlate with occupancy rather than weather, and they sometimes carry an odour or a soap film that groundwater does not. A perimeter drain discharging incorrectly, a broken storm line, or an irrigation supply are all candidates.

Distinguishing them costs almost nothing. It requires someone to record the date, the depth, and the recent weather each time the pit is checked, over a single wet season. Most buildings with a chronic pit problem have never done this, which is why the same question gets re-argued at every council meeting.

Hydrostatic pressure is the hard case

Where the source is groundwater, the water is not merely present. It is under pressure, and the pressure increases with depth below the water table.

That changes what a repair has to do. A coating that resists water arriving on a surface is not the same as a system that holds back a standing head of water pushing continuously against the inside face of a wall. Products and details that perform well on a deck can fail immediately in this application.

The ideal fix is waterproofing on the outside face of the below-grade structure, where the water is, because that keeps water out of the concrete altogether. On an existing building that means excavating alongside the foundation, which on a downtown site with adjacent buildings, services, and a street is frequently impractical and always expensive.

The alternative is working from inside, which is the approach described in the post on negative-side waterproofing below grade. Crystalline systems, cementitious coatings, and injection at active leaks all have a role, and all of them are holding water back rather than keeping it out of the structure. That distinction matters for the reinforcing steel inside the wall, which stays wet either way.

What the water is doing while you decide

Standing water in a pit is not a neutral condition being managed.

It corrodes elevator equipment, some of which sits low in the pit and was never intended for immersion. It creates an electrical hazard in a space with power in it. And it saturates the concrete of the pit structure continuously, which drives the corrosion mechanism described in the post on rebar corrosion and concrete delamination, in a location where nobody inspects the concrete because the pit is a service space.

On a tower, the failure mode that finally forces action is usually an elevator out of service rather than any of the above. By then the pit structure has often been wet for years.

Choosing the pump deliberately

For a substantial number of Metro Vancouver buildings, a properly specified sump and pump is the honest answer. Excavating the exterior of a below-grade wall to install waterproofing that should have gone on during construction is disproportionate to the problem on many sites.

The important word is deliberately. A pump chosen as the solution comes with an alarm, a maintenance schedule, a plan for what happens during a power failure, and in many cases a backup unit. A pump that a building drifted into after fifteen years of pumping the pit every few months has none of those, and it fails during the storm that fills the pit fastest.

Where a pump is the plan, the associated envelope work is usually worth doing anyway: correcting site grading and perimeter drainage so less water reaches the structure in the first place, which is covered in the guide on site grading and perimeter drains. Reducing the volume arriving makes the pump’s job smaller and buys margin for the day it fails.

Reducing the water before managing it

Whatever the long-term approach, the volume arriving at the structure can usually be reduced, and that work is comparatively cheap.

Site grading that directs surface water toward the building rather than away from it is common on older properties, where landscaping has been rebuilt several times and levels have drifted. Correcting it is landscaping work rather than building work.

Downspouts discharging at the base of a wall, rather than into a drainage system, deliver a concentrated volume of roof water directly against the below-grade structure. Extending them or connecting them properly is straightforward and it removes a large proportion of the water in many cases.

Perimeter drains that were installed at construction and have since silted up, been crushed, or filled with roots stop performing without anything visible changing. Their condition can be assessed by camera, and cleaning or replacing a failed perimeter drain addresses the source rather than the symptom.

All three are covered in the guide on site grading and perimeter drains, and all three should be checked before anyone prices an injection programme.

Living with a managed pit

Where a pump is the accepted solution, a few provisions turn it from a liability into a controlled arrangement.

An alarm that reports to somebody, rather than a light in a service room nobody enters. A maintenance schedule that includes testing the pump under load rather than confirming it is plugged in. A record of how often it runs, which is the trend information that shows whether the situation is stable or worsening.

A plan for power failure, because the storm that fills the pit fastest is the one most likely to take the power out. Depending on the building, that means a backup unit, a generator connection, or an accepted understanding that the elevator goes out of service during an extended outage.

And periodic inspection of the pit structure itself, which is the part that gets forgotten entirely. The concrete in a pit that has been wet for a decade is deteriorating, and nobody is looking at it because the pump is handling the water.

Who to call

Not the elevator contractor, for the cause. They should stay involved for the equipment, and their observations about how quickly the pit refills are genuinely useful data.

The assessment belongs with someone who works on below-grade waterproofing, and on a persistent or worsening problem, with a building envelope engineer. The questions to be answered are where water is crossing the structure, under what pressure, and whether the source is groundwater or a service, and none of those are mechanical questions.

Getting that answer first is what prevents the common outcome: several thousand dollars of injection work at the visible seepage in the pit wall, which stops that one leak and does nothing about the water still arriving from somewhere else.

Sources and further reading

• BC Housing, Building Enclosure Design Guide, below-grade waterproofing and drainage provisions, referenced 2026
• National Research Council Canada, National Building Code of Canada, foundation drainage and dampproofing requirements, referenced 2026
• Canadian Standards Association, CSA B44 Safety Code for Elevators and Escalators, elevator pit condition requirements, referenced 2026
• Allweathercoating below-grade assessment records, Metro Vancouver, 2026