Lift pit leak sealing and tanking

Why lift pits fill up, and why yours may not be the source

Before anything gets sealed, the water has to be attributed. A pit is a collection point, so the visible water is frequently arriving from somewhere that has nothing to do with the pit structure. Sealing the pit walls when the water is running down the shaft from a car park wash bay produces a very tidy invoice and no result.

The usual sources, roughly in the order we find them:

• The kicker joint, which is the construction joint where the pit wall meets the pit floor slab. This is the single most common genuine path and it is a joint, not a crack, so it takes closer packers and more resin than people expect.
• Construction joints and tie-bolt holes in the pit walls, particularly where the pit was poured separately from the basement slab and the waterstop failed or was never installed.
• Groundwater under head, where the pit floor sits below the water table. In that case the pit is not leaking so much as being pushed into, and the pressure does not go away when the crack is sealed.
• Water arriving from above: shaft wash-down, a car park being hosed, a leaking service riser, a fire sprinkler test, or a basement slab draining toward the shaft opening.
• A failed, undersized or disconnected sump pump, which is not a leak at all but is very often the actual reason the pit is wet this month when it was dry last year.
• General seepage through porous concrete across the pit floor or lower walls, with no defined line. That is a tanking problem, and injection on its own will not touch it.

AS 2865 is a law, not a line item you can negotiate away

A lift pit meets the definition of a confined space: an enclosed or partially enclosed space, with restricted means of entry and exit, not designed to be occupied by a person, that may contain a contaminated atmosphere or an oxygen deficiency. Nothing about that definition depends on how deep the pit is or how long the job takes.

What compliance actually requires on site is specific. A written entry permit for each entry. Atmospheric testing before entry and monitoring during it, by a competent person, with a calibrated detector. A standby person stationed at the top for the whole entry, who does not perform productive work and does not leave. A means of communication with the person inside. Forced ventilation where testing or the work requires it, which injection in a pit generally does. A rescue plan and the rescue equipment to execute it, on site, before entry, not on a truck across town.

We itemise that at $800 to $2,000 per day, over and above the base scope. It covers the extra body, gas detector hire and calibration, permit administration, rescue gear and tripod or winch, forced ventilation, and the genuine productivity lost to entry and exit cycles. It is a cost, not a margin grab, and it is shown separately precisely so a building manager can see what it is and compare it against another quote.

Two other exposure standards bite harder in a pit than anywhere else on a building, because a pit has no air movement at all. Drilling concrete releases respirable crystalline silica, workplace exposure standard 0.05 mg per cubic metre over eight hours, so we drill with on-tool extraction or wet. Uncured polyurethane contains isocyanates, exposure standard 0.02 mg per cubic metre over eight hours and 0.07 mg per cubic metre over 15 minutes, and sensitisation to isocyanates is permanent, so respiratory protection is fit-tested and the pit is force-ventilated during injection.

The lift contractor isolates. We never touch the lift.

This division of responsibility is not a preference and it is not a way of moving cost onto someone else. The lift is a registered item of plant with its own service contractor, its own controls and its own maintenance history. Isolation and lock-out belong to that contractor, and the sequence only runs in one direction.

1. The outage is booked with the lift contractor firstTheir availability, not ours, usually sets the date. In an occupied building with a single lift car, that can mean weeks of lead time and often out-of-hours work. Booking the waterproofer before the lift company is the commonest reason a pit job gets rescheduled.
2. The lift contractor isolates and locks outFormal isolation, locked and tagged, with the car secured. We do not accept the car being parked upstairs as isolation, we do not accept a verbal assurance from a building manager, and we do not enter on the basis that the lift has been switched off at a panel.
3. Our entry permit is issued after isolation is confirmed, not beforeAtmospheric testing, standby person in position, ventilation running, rescue equipment set, then entry. The permit references the isolation, so the two documents are tied together.
4. We hand back to the lift contractor, not to the buildingAt the end of the works, and again after the observation period, the pit is handed to the lift contractor to inspect and recommission. Any equipment in the pit that needs re-testing, adjustment or replacement after being wet is theirs, and it should be scoped by them.

Oil is the reason most pit repairs fail

Buffer oil, hydraulic jack oil and gearbox weep end up in the bottom of a pit. It is normal, it is common, and it is the single most frequent cause of a failed lift pit repair. Oil in and on the substrate acts as a bond breaker. Resin will not key into an oil-contaminated crack face, coatings will not adhere to an oil-contaminated slab, and neither failure shows up on the day. It shows up as a wet pit three months later and an argument about whose repair failed.

So the pit is degreased, and the degreasing is checked before anything else goes on. That means removing the standing oily water and silt, cleaning the substrate mechanically and with an appropriate degreaser, then testing that the surface will actually accept a bond rather than assuming it. On a pit with heavy contamination this is a genuine part of the programme, not a wipe-down at the start of the day.

There is a corollary worth stating plainly. If oil is arriving in the pit because a hydraulic lift has an active leak, that is the lift contractor's scope and it needs to be fixed first. Sealing and coating a pit that is still being oiled from above is money spent on a surface that will be contaminated again before the next wet season.

The sequence in a pit

1. Dewater and clean outPump down, remove silt, debris and any oily residue, and expose the substrate so the actual paths are visible rather than inferred. A pit inspected full of water has not been inspected.
2. Degrease and prove the substrateAs above. No resin and no coating goes onto contamination, and this step is done before the scope is finalised because what it reveals often changes the scope.
3. Chase the joint, not the wallThe kicker joint where the pit wall meets the floor slab is usually the real path, even when a crack higher up the wall is what you can see. Drill 13 mm holes at 45 degrees to intersect that joint at mid-depth, offset from the joint line by roughly half the element thickness, to two-thirds or three-quarters of the depth and never through.
4. Mechanical packers at 200 to 400 mm centresCloser on tight or hairline paths, wider on an open joint. As a rule the spacing should not exceed the thickness of the element being injected. Surface ports glued to a wet pit wall will not adhere and are not used here.
5. Flush to prove the joint is connectedWater pumped through each packer proves travel to the next one, clears laitance and salt deposits from inside the joint, and pre-wets the path so a moisture-cured resin has water to react with. If it does not travel, the set-out changes before any resin is mixed.
6. Inject hydrophobic polyurethane, bottom to topHydrophobic because a pit cycles between wet and pumped-dry and a dimensionally stable closed-cell foam will not shrink when it dries out. Accelerator dosed at roughly 1 to 10 per cent by volume gives 20 seconds to several minutes of gel, so a running point is killed fast and a fine joint is given time to travel. Start low on pressure inside the 35 to 140 bar working band and escalate only as the joint requires.
7. Budget the resin per packer and mean itIf resin disappears into a void or a drainage layer behind the pit wall without pressure building, we stop at a hard limit of 1 to 2 litres at that packer and move on rather than pumping a drum into the ground. Injecting a thin pit floor under hydrostatic uplift can also heave and crack it, which is a much larger problem than the leak.
8. Tank only where seepage remainsWhere the pit sits below the water table and general seepage continues through porous concrete after the defined paths are sealed, a negative-side crystalline or cementitious tanking system goes over the injected substrate. Injection kills the lines, tanking handles the body. Doing the coating first, over unsealed joints, is how pits get painted twice.
9. Cut back at 24 hours, then watchPackers stay in a minimum of 24 hours, are cut back below the surface, and the recesses filled with a non-shrink hydraulic plug. Then the observation period starts, and the pit is not handed back until it has run.

When a wet pit does not need injecting

Roughly one pit enquiry in four turns out to be something other than a leaking pit structure, and the honest call is worth more to a building manager than the job is worth to us. These get ruled out before we quote injection.

• A failed, undersized or disconnected sump pump. If the pit structure is sound and the pump has stopped keeping up, that is a mechanical and electrical scope. Check the float, the discharge line and where it actually discharges to before anyone drills anything.
• Water arriving from above rather than through the walls. Car park wash-down, a hosed basement, a fire sprinkler test, a leaking riser or a slab draining toward the shaft opening. Inspect the shaft during and after rain, and during a wash-down, before attributing the water to the pit.
• A leaking pipe or service. Pressure-test it. This is quick to rule out, cheap to fix compared with a pit programme, and expensive to get wrong.
• Condensation rather than ingress. A sealed shaft in a humid Queensland summer, with cold surfaces and no ventilation, produces genuine water with no correlation to rain at all. Injection achieves nothing and the building is worse off by the cost of it.
• Broad-area seepage through the pit floor with no defined line, under a permanent water table. Injection has nothing to grip. That is a tanking scope, or a designed drained-and-pumped pit, and it should be quoted as one from the start rather than discovered after two days of drilling.
• A pit that is wet because the building's subsoil drainage has failed. Sealing the lowest point in a building without asking where the groundwater is now going raises the head against everything else below ground.

What a pit costs, itemised

The complete band for a single pit in South East Queensland metro is $2,500 to $12,000 excluding GST. That is a wide band because the drivers genuinely differ by an order of magnitude between a dry-season crack seal in an accessible basement and an oil-contaminated pit under a hotel needing night access and a tanking system over the injection. The itemised lines below are what actually move a quote inside that band.

48 hours of watching before we hand it back

A pit is one of the few structures in this trade where the repair can genuinely be tested rather than argued about. The geometry does the work for you: dewater it, and anything still arriving has to show itself.

So the pit is pumped down and observed for a minimum of 48 hours after the packers are cut back, ideally spanning a rain event. Moisture readings are taken at marked points before and after so there is a number rather than an opinion. Photographs are taken before and after from the same positions, alongside a written description of what we found and what we did.

That record goes to the building manager and, where the building is strata, to the body corporate. It is the evidence for a warranty claim, the basis for a supplier claim if a product underperforms, and the thing that resolves the next argument in minutes. Then the pit is handed to the lift contractor to inspect and recommission, and anything in the pit that has been sitting in water is theirs to assess.

If water comes back, it may not be the same leak

This is the one thing about lift pits that is genuinely different from every other injection job, and it deserves to be said before the work rather than after it. The pit is the lowest point in the building. It collects everyone's water. A leak that reappears in a sealed pit is very often a new source, not a failed repair.

We have seen a pit sealed successfully in March and wet again in December because a car park drain upstream blocked, because a riser started weeping two levels up, or because the site's subsoil drainage silted up and the water table came up with it. None of those are injection failures and none of them would be fixed by injecting again.

The before and after photographs are how that gets settled without a dispute. If water is arriving at a path we treated, that is ours and we come back. If it is arriving somewhere we never touched, it is a new scope and the record shows it in minutes. Sealing from the dry side redirects water; it does not remove it, and no honest warranty in this trade covers a path that did not exist when the work was done.

What it costs

Indicative only, and excluding GST. Build a line-by-line estimate for your own job with the price book, or read the working behind the rates in the 2026 cost guide.

Questions we actually get asked

How long is the lift out of service?

Typically 1 to 3 days on site, plus the observation period, plus whatever lead time the lift contractor needs to book the isolation. In practice their availability sets the date more often than ours does. Where the pit needs a tanking system over the injection, add curing time before recommissioning. In a building with a single lift car we will usually recommend running the works after hours or across a weekend, which carries a labour loading of 30 to 100 per cent but takes the outage out of the tenants' day.

Can you work in the pit with the lift still running?

No, under any circumstances. Entry only happens after the lift contractor has formally isolated and locked out the lift, and after our own confined space permit is issued against that isolation. We do not accept the car being parked upstairs, a switch thrown at a panel, or anyone's verbal assurance. If a contractor offers to work around a live lift to save you an outage, that is not efficiency.

The pit was coated with a waterproof paint last year and it is wet again. Why did that fail?

Three reasons account for nearly all of them. First, oil contamination: buffer and hydraulic oil in the substrate stops any coating bonding, and the coating lifts. Second, the defined leak paths were never sealed, so a coating was applied over a live joint and water pressure simply pushed it off from behind. A negative-side coating has to be applied over a substrate where the water has already been stopped, not instead of stopping it. Third, hydrostatic pressure where the pit sits below the water table, which a thin coating with no key into the concrete cannot resist. Sequence matters here: inject the joints, then coat, never the reverse.

Our pit has a pump that runs constantly. Isn't that a solution?

It is a symptom, and often it is the thing that is about to fail next. A sump pump cycling continuously is running well beyond its duty, and burnt-out pit pumps are one of the commonest ways a pit floods and takes the lift out of service. That said, there is a legitimate case where pumping is part of the design: a pit permanently below the water table may always need a functioning pump, and injection's job there is to reduce the inflow to something the pump handles comfortably rather than to eliminate it. We will tell you which of those two situations you are in before quoting.

Is the confined space cost really unavoidable, or is it padding?

It is unavoidable, and the reason is legal rather than commercial. A lift pit is an enclosed space with restricted entry and exit that was never designed as a workplace, which places it inside AS 2865 and the work health and safety regulations. That requires a written entry permit, atmospheric testing before and during entry, a standby person who does not do productive work, communications, and a rescue plan with equipment on site. It genuinely adds a person and setup time, which is why we show it as $800 to $2,000 per day rather than folding it into a rate. A contractor quoting a pit without it is either not doing it, or doing it and not telling you what it cost.

There is oil in the bottom of our pit. Does that change the scope?

Yes, materially. Buffer and hydraulic oil is a bond breaker: resin will not key into an oiled crack face and no coating will adhere to an oiled slab. The pit has to be degreased and the substrate proven before anything is injected or applied, and that is a real line on the quote. It also raises a question for your lift contractor, because if oil is still arriving from a leaking hydraulic jack or a weeping gearbox, that leak needs fixing before we seal anything or the substrate will be contaminated again. Oil in the pit is the single most common cause of a failed pit repair and it is worth photographing and sending with your enquiry.