Lift Pit Waterproofing: Stop the Water, Do Not Just Pump It
Lift pit waterproofing stops water entering the lowest point of the building. The Armstrong system has three parts. Running entry points are stopped with RAPIDSTRONG GROUT PU injection or RAPIDSTRONG PLUG 31. Cold joints and honeycombs are repaired with ROOFEX GP, ROOFCRETE AR or ROOFCRETE MC 240. The pit floor and walls are then lined in two coats of ROOFEX COP crystalline coating, or of ROOFCOAT FLEXI 100 or ROOFBOND RFX PLUS 210 where movement is expected. A pump alone only removes water that has already entered.
By Armstrong Chemicals Pvt. Ltd. · ISO 9001:2015 certified · Protecting buildings, roofs and structures since 1982
Section 1 of 10: Start here
1
Check
Water, timing, entry points
2
Route
Match your pit
3
Stop and repair
Inject, plug, rebuild
4
Line and test
Two coats, cure, watch
Step 1
Water in the lift pit: check these five things first
Standing water at the bottom of the lift shaft, a pump that runs after every rain, rust on the buffers and guide rails, a damp line at the pit floor and wall joint, and lift faults in the monsoon are the usual signs of lift pit leakage. The pit is the lowest point of the building. It is cast as a step below the basement raft, so water held in the soil after rain drains towards it and presses on its walls and floor before it reaches anything else. Lift pit waterproofing means stopping that water where it enters. Five checks decide the lift pit leakage solution.
A pump is not waterproofing. A pump removes water that is already inside the pit. It does not stop it entering, it stops in a power cut, and the pit walls stay wet and under pressure between pump runs. Keep the pump as a backup. The fix is to close the entry points and line the pit.
A lift pit is a small concrete box set below the basement floor, with more joints for its size than any other part of the building. Each numbered point is treated before the lining goes on.
1
Does the water return after pumping?
Pump the pit dry and watch. If the level comes back within hours, water is coming through the concrete. If it stays dry until someone washes the floor above, the source is inside the building.
2
Does it follow the rain?
Water that returns a day or two after heavy rain is storm water held in the soil around the pit. Water all year points to a wet site, a leaking water line or a drain nearby. Check both.
3
Is water running in, or seeping?
A trickle or jet at one point is stopped first. Seepage along a joint or through the wall is injected or repaired. Mark each one while the pit is wet.
4
Where does it enter?
Look at the joint between the raft and the pit wall, the pit floor and wall joint, the holes where the buffers are anchored, honeycombed concrete, cracks and conduit entries.
5
What are the pit walls made of?
Most pits are RCC. Some older pits have brick or stone walls, which need a lining that suits masonry.
Step 2
Find the right lift pit waterproofing method
Match your pit to one route. Site work in a lift pit is done by an Armstrong applicator or distributor with the lift taken out of service by the lift company.
Route A
Water is running in at a point or a joint
The flow is stopped first. A point is plugged and a running joint or crack is injected with a water-reactive grout.
Route B
Standing water that returns after pumping
Every entry path is found, injected and repaired, then the whole pit is lined in two coats.
Route C
Damp walls and floor, no standing water
The joints and any honeycombs are repaired and the pit is lined before the problem grows.
Route D
Brick or stone pit walls
The walls are stripped and repaired, then lined with a coating that suits masonry.
Route E
New lift pit being built
Watertight concrete, treated joints and a lining before the lift is installed.
Route F
Lined before and flooding again
Find the missed path and the source of the water before anything is re-coated.
Not sure
Let the finder suggest a route
Answer three questions and see a starting recommendation.
Stop the water. Do not just pump it. Entry points first, repairs second, lining last, on every route.
Step 3
Lift pit waterproofing system finder
Answer three questions for a starting recommendation, then confirm it with an Armstrong expert. Every lining shown suits the pit described.
1
What do you see in the pit?
2
When does the water appear?
3
What is the pit like?
Answer all three questions to see the recommended starting point.
Do the work
Seeping concrete: grout through drilled holes before any lining goes on
When water leaks, seeps or sweats through porous, honeycombed or cracked concrete, it has to be stopped inside the concrete first. This is the standard negative-side method for tanks, pools, basements, lift pits and retaining walls. A lining laid over concrete that is still seeping is pushed off by the water behind it: it blisters, lifts and fails. Grouting through drilled holes fills the internal voids and capillaries along the path of the water, so the surface is dry and sound before the coating or membrane goes on. Doses, thicknesses and coats are the standard figures; the site and the exposure decide where they move.
1
Drill the injection points
Drill 12 to 14 mm holes with an electric drill into the leaking or honeycombed zone, to the depth the member needs (14 to 16 mm on thick retaining walls).Why: The holes intercept the pathways the water is travelling along, so the grout reaches the voids instead of just sitting on the surface.
2
Fix the nozzles
Fix a rubber injection nozzle in each hole with a quick-setting putty of cement mixed with the set accelerator RAPIDSTRONG QS 113. For active flow, the single-component plugging compound RAPIDSTRONG PLUG can be used to fix the nozzle instead.Why: The nozzle must be locked into the hole before pumping starts. If it is not, the pressure blows it out and the grout runs back out of the hole.On site: The datasheet gives RAPIDSTRONG QS 113 at 500 ml to 2 L per 50 kg of cement and asks for a site trial, so trial the dose on the job before fixing every nozzle.
3
Seeping or sweating concrete: cement slurry
Mix a cement slurry with a non-shrink grout additive and pump it into each nozzle with a grout pump at about 140 psi, until that point refuses to take any more. Any of three additives can be used: RAPIDSTRONG GROUT ADMIX at 250 g per 50 kg of cement, RAPIDSTRONG GROUT PB 66 (a polymer grout additive, dosed as on its datasheet) or ROOFEX GP (a crystalline grout compound, dosed at 250 g per 50 kg of cement).Why: The slurry fills the internal voids and capillaries. The additive keeps it from shrinking away from the concrete as it sets, which an ordinary cement slurry does, and the crystalline option also seals the capillaries.On site: Work from the lowest nozzle upward on a wall, so the slurry pushes the water and air out ahead of it.
4
Running or gushing water: polyurethane resin
Where water is flowing or gushing, cement slurry would simply wash away before it sets. First stop the surface flow with RAPIDSTRONG PLUG in a V-groove, then inject RAPIDSTRONG GROUT PU, the single-component polyurethane grout, with air-compressed injection equipment at about 500 g per grout point.Why: The polyurethane reacts with the water itself, expanding and stiffening to block the flow, so it works where cement cannot.On site: A hard-working point can take 0.3 to 0.75 kg. Polyurethane grouting alone only stops the flow; it is not a guaranteed waterproofing system, so follow it with the lining or coating the structure needs.
5
Remove the nozzles and seal
Once grouting is complete, remove the nozzles and patch every hole flush with a putty of ROOFCRETE AR and cement.Why: This leaves a smooth, sound, watertight surface ready for the final lining.
6
Check before lining
Look at the face again after the grout has set. Any point still wet gets another nozzle beside it before the coating, membrane or plaster goes on.Why: A single wet patch left behind becomes the first blister under the new lining.
Lift pit leakage solution: stop the entry points and repair the joints
The work is done inside the pit with the lift isolated. The pit is pumped dry, cleaned of silt and oil, and everything loose is removed back to sound concrete. Only then can the entry points be seen. A lift pit has a short list of places where water gets in, and each has its own treatment.
Raft to pit wall joint
Why it leaks there
The pit wall is cast on a hardened raft. The joint is a plane of weakness at the lowest point
How to stop water coming into a lift pit, step by step
1
Take the lift out of service
The lift company isolates the lift and protects or removes the equipment in the pit. Waterproofing work does not start until they have handed the pit over.Why: Work in a pit with live equipment is unsafe, and water and repair materials can damage the lift gear.
2
Pump out and clean
Remove water, silt and oil. Strip loose and flaking material from the walls, floor and joints.Why: Seepage can only be seen and repaired on a clean, dewatered surface, and silt and oil block every repair material.
3
Map the entry points
With the pit just pumped, water shows where it enters. Mark each point and each damp joint against the table above.Why: With the pit just pumped, water shows exactly where it comes in, so each point is marked while it still shows.
4
Close them in order
Plug point leaks, inject the running joints, open and fill the raft joint, then rebuild honeycombs. Armstrong grouting is done with 12 to 14 mm holes (14 to 16 mm on thick retaining walls) fitted with pressure packers about 75 mm long, fixed with RAPIDSTRONG PLUG. The PU grout is injected with an air-compressed unit at about 500 g per grout point, and the holes are sealed with ROOFCRETE AR and cement after the packers are removed.Why: Plugs and injection stop the water first, then joints and honeycombs are rebuilt, so each repair has a still surface to bond to.
5
Deal with the buffers and sleeves
Pack around buffer anchors, ladder fixings and conduit sleeves with non-shrink grout. Mixed grout is used within 30 minutes.Why: The anchor and sleeve holes pass through the floor and walls, and unsealed they let water in round every fixing.
6
Form the fillet
Round off the pit floor and wall joint with repair mortar so the lining does not turn a sharp corner.Why: A lining cannot turn a sharp corner without cracking, so the floor and wall joint is rounded off.
Below ground, the same rule applies. Water pushes from the soil side, so a coating on the soil side holds and a thin film on the inside is pushed off. When only the inside can be reached, the concrete itself is sealed with a crystalline coating after the leak paths are injected. The full explanation, with the positive side and negative side options compared, is on the basement waterproofing page.
Do the work
Lift pit waterproofing coating: lining the floor and four walls
With the entry points closed, the pit is lined as one box: the floor, the fillet and four walls, without a break at the corners. On a finished building only the inside can be reached, so the lining is a negative side lining and must not be a paint that water can lift from behind. The right lining depends on the state of the pit.
Sound RCC pit
Crystalline lining
ROOFEX COP, ROOFEX or RAPIDSTRONG EC 211 brushed on dampened concrete. The crystals grow in the pores, so the barrier is inside the wall. It works on pits that stay wet.
ROOFEX 2K 711 is compatible with brick and stone under negative pressure, and is made for 10 to 12 bar of water pressure.
The pit floor and wall joint carries the most stress. It gets a fillet, and the lining runs over it without a break.
How to apply lift pit waterproofing, step by step
1
Check the repairs
No running water, every joint filled, anchor holes grouted, fillet formed.Why: No running water should remain before lining, as water behind a lining pushes it off.
2
Prepare the surface
Dampen the concrete for a crystalline lining. Leave a flexible lining on a clean surface as its data sheet says.Why: A crystalline lining needs a damp surface to form crystals, while a flexible lining needs a clean one to bond.
3
Line the floor, fillet and walls
Two coats, the second at right angles to the first. Take the lining up the shaft wall to a height the engineer agrees.Why: Two coats crossed at right angles close the pinholes in the first, and lining the shaft walls above stops water finding a way round.
4
Cure for a closed space
A pit has no through air. Mist crystalline coats and keep a little air moving so the coating cures evenly.Why: A pit has no through air, so the lining is cured by misting and some air movement, or it will not cure properly.
5
Test before the lift returns
Stop the pump and watch the pit through the next heavy rain, or for an agreed period, before the equipment is refitted.Why: The pit is watched through a heavy rain before the lift returns, since a leak found afterwards means taking it out of service again.
Do the work
New lift pit waterproofing during construction
A new lift pit is the easiest pit to keep dry, because the concrete, the joints and the outside faces can all be treated before the lift arrives. Most leaking pits were cast in a cramped excavation, poorly compacted and left untreated at the joint with the raft.
1
Add an integral waterproofing compound to the concrete
Clean the hardened face before the next pour and apply a bond coat of ROOFBOND SBR 401 or ROOFBOND EP while it is still tacky. ROOFEX is applied at the construction joints.Why: Joints are where a pit leaks first, so they are cleaned and bonded as they are cast.
3
Compact the pit walls well
A pit is narrow and hard to vibrate. Honeycombs low on the wall are the usual result. Take extra care at the base.Why: A pit is narrow and hard to vibrate, so honeycombs form low on the walls, and compaction closes them.
4
Cure the concrete
Cure for the full period. ROOFEXCURE WB is a spray-applied curing compound for faces that are hard to keep wet. Do not use it on faces that will take a crystalline lining: ROOFEX and ROOFEX COP are applied to bare concrete and cured with water.Why: Concrete that dries early is porous, and a curing compound reaches faces that are hard to water.
5
Coat the outside while it can be reached
Where the outer faces of the pit are open before backfilling, they are coated as for a basement wall. See basement waterproofing.Why: The outer faces can only be reached before backfilling, and a coat there keeps water out of the concrete altogether.
6
Grout every fixing and sleeve
Buffer anchors, ladder fixings and conduit sleeves are packed with non-shrink grout made with RAPIDSTRONG GROUT ADMIX.Why: Anchors, ladder fixings and sleeves pass through the concrete, and non-shrink grout closes the gap round each one.
7
Line the inside before the lift is installed
Form the fillet and apply the lining in two coats, then moist cure. It is far easier now than after the equipment is in.Why: The lining goes in before the lift is installed, while the whole pit is clear and can be reached.
Do the work
When the lift pit floods again: missed paths, the water source and the last resort
A pit that takes in water after treatment has usually been lined without all its entry points being closed, or it is being fed by a source that was never looked at. Work up the ladder one rung at a time. Breaking out and recasting the pit is the extreme case and comes last.
1. Find the missed path
Pump out and map again. The raft and pit wall joint and the buffer anchor holes are the points most often missed.
2. Re-inject and re-line that zone
Joints injected with RAPIDSTRONG GROUT VM 99 can be injected again. Repair, then re-coat over the area.
3. Cut off the source
Check basement floor drains, wash water, a leaking water line, the car park ramp drain and any sump that overflows towards the shaft.
4. Rebuild the pit lining
Only if the pit concrete itself is too weak to hold a repair: an inner RCC lining is cast inside the pit to an engineer's design, with watertight concrete.
Pump
Keep the pump, as a backup
After the pit is sealed the pump should rarely run. A pump that still runs often is a sign that a path is open.
Steel
Rusted reinforcement and broken concrete
Where long flooding has rusted the steel and broken the concrete, the repair follows the steel repair sequence. See structural concrete repair.
Work out the quantity for your own job. Enter your measurements and get the material needed.
How much waterproofing material for a lift pit
Approximate quantities for a pit 8 ft long, 7 ft wide and 5 ft deep. The floor is 56 sq.ft and the four walls come to 150 sq.ft, a total of 206 sq.ft or about 19 sq.m. Figures are worked out from each product's stated coverage. Injection grout, plugging compound and repair mortar depend on the leaks found and are measured at site. An Armstrong expert confirms the final quantity after seeing the site.
ROOFEX COP, two coats
Stated coverage
0.75 to 1 sq.m per kg per coat
For this pit
39 to 52 kg
ROOFEX, two coats
Stated coverage
0.75 kg per sq.m per coat
For this pit
About 29 kg
ROOFEX 2K 711
Stated coverage
1.2 to 1.6 kg per sq.m in total
For this pit
23 to 31 kg
ROOFCOAT FLEXI 100, two coats
Stated coverage
20 to 30 sq.ft per litre for two coats
For this pit
6.9 to 11 litres, plus 14 to 21 kg of cement
ROOFBOND RFX PLUS 210, two coats
Stated coverage
13 to 14 sq.m per 20.1 kg unit
For this pit
2 units
Standards and tests behind lift pit waterproofing products
The test standards behind the injection grouts, crystalline coatings and flexible linings are listed on the basement waterproofing page, because the same products are used.
CONPROOF LW 200 and CONPROOF 500 conform to IS 2645:2003 for the concrete of a new pit.
Lift work in the pit, including isolation and refitting, is done by the lift company to its own safety rules.
Reference
Lift pit waterproofing material calculator
Enter the size of the pit to see the lining needed for the floor and four walls. Quantities only. Injection grout, plugging compound and repair mortar depend on the leaks found and are measured at site.
1
Choose your units
2
Enter the measurements
3
Which lining?
Enter the measurements to see the estimated quantity of material.
Reference
Seven mistakes that bring water back into a lift pit
Relying on the pump. It removes water and stops nothing. The concrete stays wet and the pump fails when the power does.
Lining over running water. The lining lifts at that point. Plug or inject first.
Leaving the raft and pit wall joint untreated. It is the main entry path and needs injection and repair, not a brush coat.
Leaving buffer anchor holes unsealed. Each hole is a path through the pit floor.
Painting the pit with a surface film. Water behind the wall pushes it off, and it bubbles and flakes.
Lining over plaster, oil or silt. A crystalline lining must touch clean concrete. Remove everything loose and old.
Refitting the equipment before testing. Watch the pit through a wet spell first.
Lift pit waterproofing questions and answers
Which chemical is used for lift pit waterproofing?
Because the pit is the lowest point of the building. Water held in the soil after rain drains towards it and presses on its floor and walls first. The rest of the basement can be dry while the pit fills.
Is a pump enough to keep a lift pit dry?
No. A pump takes out water that has already come in. It does not stop it entering, it stops when the power fails, and the walls stay wet between runs. Keep it as a backup after the pit is sealed.
Does the lift have to stop during lift pit waterproofing?
Yes. The lift company isolates the lift and protects the equipment in the pit before work starts, and refits it afterwards. The time out of service depends on the leaks found and the curing of the lining, and is agreed with the applicator and the lift company before work starts.
How do I stop water coming into a lift pit?
Pump out and clean the pit, mark where water enters, plug point leaks, inject running joints and cracks with a water-reactive grout, rebuild the joints and honeycombs, form a fillet at the floor and wall joint, then line the floor and walls in two coats and moist cure.
Can lift pit leakage be fixed from inside?
Yes. On an existing building the pit can only be reached from inside. Injection closes the paths and a crystalline lining seals the concrete from within.
Will it hold in the next heavy rain?
A crystalline lining keeps reacting whenever the concrete gets wet, and injection closes the paths the water used. The pit is watched through wet weather before the equipment is refitted, and any point that shows damp is re-injected.
Which is best for elevator pit waterproofing, crystalline or flexible coating?
Both are used. A crystalline coating such as ROOFEX COP, ROOFEX or ROOFEX 2K 711 suits a sound RCC pit. ROOFCOAT FLEXI 100 and ROOFBOND RFX PLUS 210 are flexible cementitious linings with 120%+ elongation and suit a pit with cracks or expected movement. An Armstrong expert confirms the choice.
How is lift pit waterproofing different from basement waterproofing?
The materials are the same. The pit is deeper, tighter, has more joints for its size and holds lift equipment. See basement waterproofing for the cellar as a whole.
Can a brick lift pit be waterproofed?
Yes. ROOFEX 2K 711 is compatible with brick and stone masonry under negative pressure. The walls are stripped of plaster and repaired first.
With an integral compound such as CONPROOF LW 200 in the concrete, treated construction joints, grouted anchor holes and a lining in two coats before the lift is installed.
Is the sump next to the lift pit treated the same way?
A drainage sump is. A sump that stores water for use is lined as a water tank. See water tank waterproofing.
Get the right waterproofing system for your lift pit
Tell us the pit size, when the water appears and where it enters. An Armstrong applicator or distributor will recommend a system. Toll free 1800 103 2034. Armstrong manufactures lift pit waterproofing chemicals in Bengaluru and supplies them all across India, with South India as its major hub.
About this guide
Written by the technical team at Armstrong Chemicals Pvt. Ltd., an ISO 9001:2015 certified manufacturer of construction and waterproofing chemicals in Bengaluru, with more than 200 products. Armstrong has been protecting buildings, roofs and structures since 1982 and supplies all across India, with South India as its major hub.
The methods on this page are Armstrong's standard procedures. Doses, thicknesses and the number of coats are adjusted to the conditions on each site. Load-bearing repairs and strengthening are designed by a structural engineer.
Last updated · Questions on this method: toll free 1800 103 2034
Lift Pit Waterproofing: Stop the Water, Do Not Just Pump It
Lift pit waterproofing stops water entering the lowest point of the building. The Armstrong system has three parts. Running entry points are stopped with RAPIDSTRONG GROUT PU injection or RAPIDSTRONG PLUG 31. Cold joints and honeycombs are repaired with ROOFEX GP, ROOFCRETE AR or ROOFCRETE MC 240. The pit floor and walls are then lined in two coats of ROOFEX COP crystalline coating, or of ROOFCOAT FLEXI 100 or ROOFBOND RFX PLUS 210 where movement is expected. A pump alone only removes water that has already entered.
By Armstrong Chemicals Pvt. Ltd. · ISO 9001:2015 certified · Protecting buildings, roofs and structures since 1982
{{ posText }}
1
Check
Water, timing, entry points
2
Route
Match your pit
3
Stop and repair
Inject, plug, rebuild
4
Line and test
Two coats, cure, watch
Step 1
Water in the lift pit: check these five things first
Standing water at the bottom of the lift shaft, a pump that runs after every rain, rust on the buffers and guide rails, a damp line at the pit floor and wall joint, and lift faults in the monsoon are the usual signs of lift pit leakage. The pit is the lowest point of the building. It is cast as a step below the basement raft, so water held in the soil after rain drains towards it and presses on its walls and floor before it reaches anything else. Lift pit waterproofing means stopping that water where it enters. Five checks decide the lift pit leakage solution.
A pump is not waterproofing. A pump removes water that is already inside the pit. It does not stop it entering, it stops in a power cut, and the pit walls stay wet and under pressure between pump runs. Keep the pump as a backup. The fix is to close the entry points and line the pit.
A lift pit is a small concrete box set below the basement floor, with more joints for its size than any other part of the building. Each numbered point is treated before the lining goes on.
1
Does the water return after pumping?
Pump the pit dry and watch. If the level comes back within hours, water is coming through the concrete. If it stays dry until someone washes the floor above, the source is inside the building.
2
Does it follow the rain?
Water that returns a day or two after heavy rain is storm water held in the soil around the pit. Water all year points to a wet site, a leaking water line or a drain nearby. Check both.
3
Is water running in, or seeping?
A trickle or jet at one point is stopped first. Seepage along a joint or through the wall is injected or repaired. Mark each one while the pit is wet.
4
Where does it enter?
Look at the joint between the raft and the pit wall, the pit floor and wall joint, the holes where the buffers are anchored, honeycombed concrete, cracks and conduit entries.
5
What are the pit walls made of?
Most pits are RCC. Some older pits have brick or stone walls, which need a lining that suits masonry.
Step 2
Find the right lift pit waterproofing method
Match your pit to one route. Site work in a lift pit is done by an Armstrong applicator or distributor with the lift taken out of service by the lift company.
Route A
Water is running in at a point or a joint
The flow is stopped first. A point is plugged and a running joint or crack is injected with a water-reactive grout.
Route B
Standing water that returns after pumping
Every entry path is found, injected and repaired, then the whole pit is lined in two coats.
Route C
Damp walls and floor, no standing water
The joints and any honeycombs are repaired and the pit is lined before the problem grows.
Route D
Brick or stone pit walls
The walls are stripped and repaired, then lined with a coating that suits masonry.
Route E
New lift pit being built
Watertight concrete, treated joints and a lining before the lift is installed.
Route F
Lined before and flooding again
Find the missed path and the source of the water before anything is re-coated.
Not sure
Let the finder suggest a route
Answer three questions and see a starting recommendation.
Stop the water. Do not just pump it. Entry points first, repairs second, lining last, on every route.
Step 3
Lift pit waterproofing system finder
Answer three questions for a starting recommendation, then confirm it with an Armstrong expert. Every lining shown suits the pit described.
1
What do you see in the pit?
2
When does the water appear?
3
What is the pit like?
Answer all three questions to see the recommended starting point.
Recommended starting point
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Why this one
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Before any product goes on, the pit is pumped out and all loose, old and flaking material is removed back to sound concrete. This is a starting point, and an Armstrong expert confirms the final choice after seeing the site.
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Every product below suits this job. Pick the one that fits the site, or ask an Armstrong expert to choose with you.
Seeping concrete: grout through drilled holes before any lining goes on
When water leaks, seeps or sweats through porous, honeycombed or cracked concrete, it has to be stopped inside the concrete first. This is the standard negative-side method for tanks, pools, basements, lift pits and retaining walls. A lining laid over concrete that is still seeping is pushed off by the water behind it: it blisters, lifts and fails. Grouting through drilled holes fills the internal voids and capillaries along the path of the water, so the surface is dry and sound before the coating or membrane goes on. Doses, thicknesses and coats are the standard figures; the site and the exposure decide where they move.
1
Drill the injection points
Drill 12 to 14 mm holes with an electric drill into the leaking or honeycombed zone, to the depth the member needs (14 to 16 mm on thick retaining walls).Why: The holes intercept the pathways the water is travelling along, so the grout reaches the voids instead of just sitting on the surface.
2
Fix the nozzles
Fix a rubber injection nozzle in each hole with a quick-setting putty of cement mixed with the set accelerator RAPIDSTRONG QS 113. For active flow, the single-component plugging compound RAPIDSTRONG PLUG can be used to fix the nozzle instead.Why: The nozzle must be locked into the hole before pumping starts. If it is not, the pressure blows it out and the grout runs back out of the hole.On site: The datasheet gives RAPIDSTRONG QS 113 at 500 ml to 2 L per 50 kg of cement and asks for a site trial, so trial the dose on the job before fixing every nozzle.
3
Seeping or sweating concrete: cement slurry
Mix a cement slurry with a non-shrink grout additive and pump it into each nozzle with a grout pump at about 140 psi, until that point refuses to take any more. Any of three additives can be used: RAPIDSTRONG GROUT ADMIX at 250 g per 50 kg of cement, RAPIDSTRONG GROUT PB 66 (a polymer grout additive, dosed as on its datasheet) or ROOFEX GP (a crystalline grout compound, dosed at 250 g per 50 kg of cement).Why: The slurry fills the internal voids and capillaries. The additive keeps it from shrinking away from the concrete as it sets, which an ordinary cement slurry does, and the crystalline option also seals the capillaries.On site: Work from the lowest nozzle upward on a wall, so the slurry pushes the water and air out ahead of it.
4
Running or gushing water: polyurethane resin
Where water is flowing or gushing, cement slurry would simply wash away before it sets. First stop the surface flow with RAPIDSTRONG PLUG in a V-groove, then inject RAPIDSTRONG GROUT PU, the single-component polyurethane grout, with air-compressed injection equipment at about 500 g per grout point.Why: The polyurethane reacts with the water itself, expanding and stiffening to block the flow, so it works where cement cannot.On site: A hard-working point can take 0.3 to 0.75 kg. Polyurethane grouting alone only stops the flow; it is not a guaranteed waterproofing system, so follow it with the lining or coating the structure needs.
5
Remove the nozzles and seal
Once grouting is complete, remove the nozzles and patch every hole flush with a putty of ROOFCRETE AR and cement.Why: This leaves a smooth, sound, watertight surface ready for the final lining.
6
Check before lining
Look at the face again after the grout has set. Any point still wet gets another nozzle beside it before the coating, membrane or plaster goes on.Why: A single wet patch left behind becomes the first blister under the new lining.
Lift pit leakage solution: stop the entry points and repair the joints
The work is done inside the pit with the lift isolated. The pit is pumped dry, cleaned of silt and oil, and everything loose is removed back to sound concrete. Only then can the entry points be seen. A lift pit has a short list of places where water gets in, and each has its own treatment.
Raft to pit wall joint
Why it leaks there
The pit wall is cast on a hardened raft. The joint is a plane of weakness at the lowest point
How to stop water coming into a lift pit, step by step
1
Take the lift out of service
The lift company isolates the lift and protects or removes the equipment in the pit. Waterproofing work does not start until they have handed the pit over.Why: Work in a pit with live equipment is unsafe, and water and repair materials can damage the lift gear.
2
Pump out and clean
Remove water, silt and oil. Strip loose and flaking material from the walls, floor and joints.Why: Seepage can only be seen and repaired on a clean, dewatered surface, and silt and oil block every repair material.
3
Map the entry points
With the pit just pumped, water shows where it enters. Mark each point and each damp joint against the table above.Why: With the pit just pumped, water shows exactly where it comes in, so each point is marked while it still shows.
4
Close them in order
Plug point leaks, inject the running joints, open and fill the raft joint, then rebuild honeycombs. Armstrong grouting is done with 12 to 14 mm holes (14 to 16 mm on thick retaining walls) fitted with pressure packers about 75 mm long, fixed with RAPIDSTRONG PLUG. The PU grout is injected with an air-compressed unit at about 500 g per grout point, and the holes are sealed with ROOFCRETE AR and cement after the packers are removed.Why: Plugs and injection stop the water first, then joints and honeycombs are rebuilt, so each repair has a still surface to bond to.
5
Deal with the buffers and sleeves
Pack around buffer anchors, ladder fixings and conduit sleeves with non-shrink grout. Mixed grout is used within 30 minutes.Why: The anchor and sleeve holes pass through the floor and walls, and unsealed they let water in round every fixing.
6
Form the fillet
Round off the pit floor and wall joint with repair mortar so the lining does not turn a sharp corner.Why: A lining cannot turn a sharp corner without cracking, so the floor and wall joint is rounded off.
Below ground, the same rule applies. Water pushes from the soil side, so a coating on the soil side holds and a thin film on the inside is pushed off. When only the inside can be reached, the concrete itself is sealed with a crystalline coating after the leak paths are injected. The full explanation, with the positive side and negative side options compared, is on the basement waterproofing page.
Do the work
Lift pit waterproofing coating: lining the floor and four walls
With the entry points closed, the pit is lined as one box: the floor, the fillet and four walls, without a break at the corners. On a finished building only the inside can be reached, so the lining is a negative side lining and must not be a paint that water can lift from behind. The right lining depends on the state of the pit.
Sound RCC pit
Crystalline lining
ROOFEX COP, ROOFEX or RAPIDSTRONG EC 211 brushed on dampened concrete. The crystals grow in the pores, so the barrier is inside the wall. It works on pits that stay wet.
ROOFEX 2K 711 is compatible with brick and stone under negative pressure, and is made for 10 to 12 bar of water pressure.
The pit floor and wall joint carries the most stress. It gets a fillet, and the lining runs over it without a break.
How to apply lift pit waterproofing, step by step
1
Check the repairs
No running water, every joint filled, anchor holes grouted, fillet formed.Why: No running water should remain before lining, as water behind a lining pushes it off.
2
Prepare the surface
Dampen the concrete for a crystalline lining. Leave a flexible lining on a clean surface as its data sheet says.Why: A crystalline lining needs a damp surface to form crystals, while a flexible lining needs a clean one to bond.
3
Line the floor, fillet and walls
Two coats, the second at right angles to the first. Take the lining up the shaft wall to a height the engineer agrees.Why: Two coats crossed at right angles close the pinholes in the first, and lining the shaft walls above stops water finding a way round.
4
Cure for a closed space
A pit has no through air. Mist crystalline coats and keep a little air moving so the coating cures evenly.Why: A pit has no through air, so the lining is cured by misting and some air movement, or it will not cure properly.
5
Test before the lift returns
Stop the pump and watch the pit through the next heavy rain, or for an agreed period, before the equipment is refitted.Why: The pit is watched through a heavy rain before the lift returns, since a leak found afterwards means taking it out of service again.
Do the work
New lift pit waterproofing during construction
A new lift pit is the easiest pit to keep dry, because the concrete, the joints and the outside faces can all be treated before the lift arrives. Most leaking pits were cast in a cramped excavation, poorly compacted and left untreated at the joint with the raft.
1
Add an integral waterproofing compound to the concrete
Clean the hardened face before the next pour and apply a bond coat of ROOFBOND SBR 401 or ROOFBOND EP while it is still tacky. ROOFEX is applied at the construction joints.Why: Joints are where a pit leaks first, so they are cleaned and bonded as they are cast.
3
Compact the pit walls well
A pit is narrow and hard to vibrate. Honeycombs low on the wall are the usual result. Take extra care at the base.Why: A pit is narrow and hard to vibrate, so honeycombs form low on the walls, and compaction closes them.
4
Cure the concrete
Cure for the full period. ROOFEXCURE WB is a spray-applied curing compound for faces that are hard to keep wet. Do not use it on faces that will take a crystalline lining: ROOFEX and ROOFEX COP are applied to bare concrete and cured with water.Why: Concrete that dries early is porous, and a curing compound reaches faces that are hard to water.
5
Coat the outside while it can be reached
Where the outer faces of the pit are open before backfilling, they are coated as for a basement wall. See basement waterproofing.Why: The outer faces can only be reached before backfilling, and a coat there keeps water out of the concrete altogether.
6
Grout every fixing and sleeve
Buffer anchors, ladder fixings and conduit sleeves are packed with non-shrink grout made with RAPIDSTRONG GROUT ADMIX.Why: Anchors, ladder fixings and sleeves pass through the concrete, and non-shrink grout closes the gap round each one.
7
Line the inside before the lift is installed
Form the fillet and apply the lining in two coats, then moist cure. It is far easier now than after the equipment is in.Why: The lining goes in before the lift is installed, while the whole pit is clear and can be reached.
Do the work
When the lift pit floods again: missed paths, the water source and the last resort
A pit that takes in water after treatment has usually been lined without all its entry points being closed, or it is being fed by a source that was never looked at. Work up the ladder one rung at a time. Breaking out and recasting the pit is the extreme case and comes last.
1. Find the missed path
Pump out and map again. The raft and pit wall joint and the buffer anchor holes are the points most often missed.
2. Re-inject and re-line that zone
Joints injected with RAPIDSTRONG GROUT VM 99 can be injected again. Repair, then re-coat over the area.
3. Cut off the source
Check basement floor drains, wash water, a leaking water line, the car park ramp drain and any sump that overflows towards the shaft.
4. Rebuild the pit lining
Only if the pit concrete itself is too weak to hold a repair: an inner RCC lining is cast inside the pit to an engineer's design, with watertight concrete.
Pump
Keep the pump, as a backup
After the pit is sealed the pump should rarely run. A pump that still runs often is a sign that a path is open.
Steel
Rusted reinforcement and broken concrete
Where long flooding has rusted the steel and broken the concrete, the repair follows the steel repair sequence. See structural concrete repair.
Work out the quantity for your own job. Enter your measurements and get the material needed.
How much waterproofing material for a lift pit
Approximate quantities for a pit 8 ft long, 7 ft wide and 5 ft deep. The floor is 56 sq.ft and the four walls come to 150 sq.ft, a total of 206 sq.ft or about 19 sq.m. Figures are worked out from each product's stated coverage. Injection grout, plugging compound and repair mortar depend on the leaks found and are measured at site. An Armstrong expert confirms the final quantity after seeing the site.
ROOFEX COP, two coats
Stated coverage
0.75 to 1 sq.m per kg per coat
For this pit
39 to 52 kg
ROOFEX, two coats
Stated coverage
0.75 kg per sq.m per coat
For this pit
About 29 kg
ROOFEX 2K 711
Stated coverage
1.2 to 1.6 kg per sq.m in total
For this pit
23 to 31 kg
ROOFCOAT FLEXI 100, two coats
Stated coverage
20 to 30 sq.ft per litre for two coats
For this pit
6.9 to 11 litres, plus 14 to 21 kg of cement
ROOFBOND RFX PLUS 210, two coats
Stated coverage
13 to 14 sq.m per 20.1 kg unit
For this pit
2 units
Standards and tests behind lift pit waterproofing products
The test standards behind the injection grouts, crystalline coatings and flexible linings are listed on the basement waterproofing page, because the same products are used.
CONPROOF LW 200 and CONPROOF 500 conform to IS 2645:2003 for the concrete of a new pit.
Lift work in the pit, including isolation and refitting, is done by the lift company to its own safety rules.
Reference
Lift pit waterproofing material calculator
Enter the size of the pit to see the lining needed for the floor and four walls. Quantities only. Injection grout, plugging compound and repair mortar depend on the leaks found and are measured at site.
1
Choose your units
2
Enter the measurements
3
Which lining?
Enter the measurements to see the estimated quantity of material.
Estimated quantity
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This is an estimate of material only, worked out from each product's stated coverage on a smooth, prepared surface. Rough or porous surfaces use more, so allow about 10% extra. Crack sealing, patch repair, plaster, coving and tiling materials are not included. An Armstrong expert confirms the final quantity after seeing the site.
Because the pit is the lowest point of the building. Water held in the soil after rain drains towards it and presses on its floor and walls first. The rest of the basement can be dry while the pit fills.
Is a pump enough to keep a lift pit dry?
No. A pump takes out water that has already come in. It does not stop it entering, it stops when the power fails, and the walls stay wet between runs. Keep it as a backup after the pit is sealed.
Does the lift have to stop during lift pit waterproofing?
Yes. The lift company isolates the lift and protects the equipment in the pit before work starts, and refits it afterwards. The time out of service depends on the leaks found and the curing of the lining, and is agreed with the applicator and the lift company before work starts.
How do I stop water coming into a lift pit?
Pump out and clean the pit, mark where water enters, plug point leaks, inject running joints and cracks with a water-reactive grout, rebuild the joints and honeycombs, form a fillet at the floor and wall joint, then line the floor and walls in two coats and moist cure.
Can lift pit leakage be fixed from inside?
Yes. On an existing building the pit can only be reached from inside. Injection closes the paths and a crystalline lining seals the concrete from within.
Will it hold in the next heavy rain?
A crystalline lining keeps reacting whenever the concrete gets wet, and injection closes the paths the water used. The pit is watched through wet weather before the equipment is refitted, and any point that shows damp is re-injected.
Which is best for elevator pit waterproofing, crystalline or flexible coating?
Both are used. A crystalline coating such as ROOFEX COP, ROOFEX or ROOFEX 2K 711 suits a sound RCC pit. ROOFCOAT FLEXI 100 and ROOFBOND RFX PLUS 210 are flexible cementitious linings with 120%+ elongation and suit a pit with cracks or expected movement. An Armstrong expert confirms the choice.
How is lift pit waterproofing different from basement waterproofing?
The materials are the same. The pit is deeper, tighter, has more joints for its size and holds lift equipment. See basement waterproofing for the cellar as a whole.
Can a brick lift pit be waterproofed?
Yes. ROOFEX 2K 711 is compatible with brick and stone masonry under negative pressure. The walls are stripped of plaster and repaired first.
With an integral compound such as CONPROOF LW 200 in the concrete, treated construction joints, grouted anchor holes and a lining in two coats before the lift is installed.
Is the sump next to the lift pit treated the same way?
A drainage sump is. A sump that stores water for use is lined as a water tank. See water tank waterproofing.
Get the right waterproofing system for your lift pit
Tell us the pit size, when the water appears and where it enters. An Armstrong applicator or distributor will recommend a system. Toll free 1800 103 2034. Armstrong manufactures lift pit waterproofing chemicals in Bengaluru and supplies them all across India, with South India as its major hub.
About this guide
Written by the technical team at Armstrong Chemicals Pvt. Ltd., an ISO 9001:2015 certified manufacturer of construction and waterproofing chemicals in Bengaluru, with more than 200 products. Armstrong has been protecting buildings, roofs and structures since 1982 and supplies all across India, with South India as its major hub.
The methods on this page are Armstrong's standard procedures. Doses, thicknesses and the number of coats are adjusted to the conditions on each site. Load-bearing repairs and strengthening are designed by a structural engineer.
Last updated · Questions on this method: toll free 1800 103 2034
