Swimming Pool Waterproofing Chemicals: Shell, Lining, Tile Bed and Grout

Swimming pool leakage: check the pool before choosing a treatment

A water level that keeps dropping, tiles coming off the wall, grout washing out of the joints, damp soil or a wet plant room next to the pool: these are the usual signs of swimming pool leakage. A pool is a water tank with a tile finish and treated water. It holds water against its floor and walls all day, so it is waterproofed the way any water-retaining structure is, and then tiled with materials that survive pool chemicals. This page covers concrete swimming pools, plunge pools, water bodies and fountains. Five checks decide the swimming pool waterproofing treatment.

Find the right swimming pool waterproofing method

Match your pool to one route. The right repair is the smallest one that reaches the real source of the leak.

Shell, lining, tile bed, grout: four layers, each doing its own job. Repair first, line second, test third, tile last.

Swimming pool waterproofing finder

Armstrong makes cementitious, polyurethane-cement and crystalline linings for pools, with the sealants, adhesives and grouts that go with them. Every one is a sound choice for its condition. Answer three questions for a starting recommendation, then confirm it with an Armstrong expert.

Swimming pool waterproofing for a new pool: shell, lining, test

Waterproofing a new swimming pool starts in the concrete and ends with a water test before the first tile is fixed. A new pool that leaks usually does so at a pipe sleeve, the floor and wall junction, a construction joint or honeycombed concrete low on the walls. Each is dealt with before the lining.

1. 1
   Put an integral waterproofing compound in the concrete

   Use CONPROOF LW 200 at 200 ml per 50 kg bag of cement, CONPROOF 500 at 500 ml per bag or CONPROOF No. 1 at 100 ml per bag. For ready-mix concrete, CONPROOF RMC ADMIX 88 is added in the transit mixer at site. Pick the one that fits the mix and ask an Armstrong expert if unsure.Why: A pool shell is under water all its life, and a compound makes the concrete dense from the start.
2. 2
   Compact and cure the shell

   Honeycombed concrete and short curing cause most new-pool leaks. Cure for the full period. ROOFEXCURE WB is a spray-applied curing compound for faces that are hard to keep wet. It is sprayed 1 to 2 hours after the concrete is placed, or straight after the shuttering is struck, at 4 to 6 sq.m per kg.Why: Honeycombs and short curing cause most new-pool leaks, and compaction and full curing close them.
3. 3
   Clean the shell and remove everything loose

   Remove laitance, shuttering oil, dust and all loose or flaking material. A lining bonds only to sound concrete.Why: The lining bonds to clean concrete, and laitance and shuttering oil stop it.
4. 4
   Grout the pipe sleeves and fittings

   Pack around every inlet, return, skimmer throat, light conduit and the main drain with a non-shrink grout made with RAPIDSTRONG GROUT ADMIX at 250 g per 50 kg of cement, used within 30 minutes of mixing. Ordinary cement slurry shrinks and leaves a gap around the pipe. Then seal the periphery of each pipe with polymer concrete made with ROOFCRETE AR 576, fix a socket around the pipe, grout the socket with the same mix and prove it with a ponding test.Why: Every inlet, return and light conduit leaves a gap through the shell, and water follows it out.
5. 5
   Repair pot holes, honeycombs and tie-rod holes

   Cut back to sound concrete and rebuild with the ROOFCRETE AR system over a bond coat of ROOFBOND SBR 401 mixed 1:1 with cement, placing the mortar while the bond coat is still tacky. Tie-rod holes and shutter joints are sealed flush with a putty of ROOFBOND SBR 401, cement and graded sand at 1:1:1, or with ROOFCRETE AR where the crew prefers a repair mortar. Where the crew batches on site, ROOFCRETE AR 576 (an admixture mixed with cement and sand) does the same job. Moist-cure repairs for at least 7 days.Why: Voids are leak paths through the shell, and a lining over a void is unsupported.
6. 6
   Treat construction joints and cracks

   Open each crack and construction joint to a 4 to 5 mm V-groove, clean it and fill it with a putty of ROOFCOAT FLEXI 100 and cement, as in a water tank. Where a joint is leaking, it is injected first. Pool cracks are filled with the acrylic polymer putty.Why: Joints and cracks move, so they get a groove and a flexible sealant.
7. 7
   Seal the expansion joints

   Movement joints in large pools are sealed with ROOFEX-SEAL PS polysulphide sealant over ROOFEXSEAL PRIMER PS / NPS, never with mortar. The porous primer is for concrete and the non-porous primer is for glazed tile, glass and steel. The joint is sized with its width twice its depth. The expansion joint sealing page gives joint sizes.Why: A movement joint in a big pool opens and closes, so it takes a flexible polysulphide sealant.
8. 8
   Form the cove

   Round off the floor and wall junction with repair mortar so the lining does not turn a sharp corner.Why: A rounded fillet lets the lining turn the corner without cracking.
9. 9
   Apply the lining in two coats

   Choose ROOFCOAT FLEXI 100, ROOFBOND RFX PLUS 210 or ROOFCOAT PU 2K. ROOFCOAT FLEXI 100 is mixed 1 litre to 2 kg of regular cement and 200 ml of water. ROOFBOND RFX PLUS 210 is mixed from the 5.1 kg of liquid and 15 kg of powder in its 20.1 kg unit. With either, brush the first coat on the dampened floor and walls, bed fibre mesh into the wet first coat along the cove and over treated joints, and apply the second coat at right angles. Both linings can be applied with fibre mesh. On a weak shell the reinforced build-up is a first coat, 45 GSM fibre mesh as layer 2, then three further coats. While the last coat is still wet, sprinkle clean sand on it, so the plaster or tile bed grips.Crystalline option: depending on the circumstances, a crystalline coating can also be used along with the lining products above: ROOFEX 2K 711 (brush or spray on the dampened surface, 1.2 to 1.6 kg per sq.m in total) or ROOFEX XL (two coats, the second while the first is still damp, kept moist for 3 to 5 days). Like the other linings, it sits under the finish. Sand is sprinkled on the last wet coat, and then the plaster or the tile bed goes on.Why: Two coats close the pinholes in the first, and the lining chosen suits the pool and its exposure. A crystalline coat grows crystals inside the concrete, so it also holds against water pressing from outside.
10. 10
    Cure, then test with water

    Let the lining cure for its own time, then fill the pool and record the level daily. ROOFCOAT PU 2K needs 3 to 5 days of air cure, ROOFBOND RFX PLUS 210 is water cured for 7 days before flood testing, and ROOFEX 2K 711 needs a minimum of 15 days before filling. Follow the longest wait that applies and confirm it with Armstrong. Tiling starts only after the pool holds water.Why: The pool is filled and the level recorded daily, since a slow leak shows only over days.

Swimming pool tile adhesive and epoxy grout for pool tiles

Pool tiles sit under water with chlorine and cleaning chemicals around them every day. Two things fail first: the adhesive bed, when water gets behind tiles fixed on dabs of mortar, and the grout, when ordinary cement grout washes out. The tile bed and the grout are chosen for constant immersion.

1. 1
   Start only after the water test

   The lining must have passed the fill test and the pool must be drained and dry enough to tile.Why: Tiles over a shell that leaks hide the leak and have to come off again.
2. 2
   Mix the adhesive

   Add the powder to the liquid, mix to a smooth paste, let it stand for 5 minutes and mix again. TILEX 351 PLUS takes 5.5 to 6 litres of liquid per 20 kg bag.Why: A smooth, rested mix bonds well, and a lumpy or stiff one leaves voids.
3. 3
   Comb a full bed

   Spread the adhesive with a notched trowel and press each tile into a full, solid bed. A 6 mm by 6 mm trowel gives an average 3 mm bed. Tiles fixed on dabs leave voids that fill with water. Fix within the 30 minute open time.Why: A full, solid bed leaves no voids under the tile, and water in a void pops the tile off.
4. 4
   Leave movement joints

   Carry every expansion joint in the shell up through the tile bed and the tiles, and seal it with ROOFEX-SEAL PS. Do not tile across a movement joint.Why: The shell moves, and a tile bed with no movement joints cracks along the same line.
5. 5
   Wait before grouting

   Allow a minimum of 24 hours after fixing before grouting.Why: Tiles need the adhesive to set before grouting, or they move.
6. 6
   Grout the joints

   For epoxy grout, mix Part A and Part B fully, add Part C and nothing else, and work it into clean joints. Apply between 16°C and 32°C. Do not use acid cleaners on the tiles before or after epoxy grouting.Why: The grout mixed in full and worked into the joints is dense, and it keeps water out of the bed.
7. 7
   Clean on time

   Scrub the tile face with clean water 30 to 40 minutes after epoxy grouting, wipe with a thick towel, and wash with soap within 24 hours. TILEXKLEEN AC / DA / LC removes cement haze from tiles grouted with cement grout.Why: Epoxy grout sets hard on the tile face and has to be cleaned in its window.
8. 8
   Protect, cure and fill

   Cover open pools from direct sunlight for 7 days after epoxy grouting. Tile adhesive needs 14 days before permanent contact with water. Fill the pool only after that, and after the wait of the lining under the tiles (see the cure and test step above). The longest wait applies.Why: Sun on fresh epoxy makes it cure unevenly, and the pool is filled only after full cure.

Tile selection for floors, walls and decks outside the water is covered on the tile fixing and grouting page.

Swimming pool leakage repair: find the leak, then seal fittings, joints and cracks

Swimming pool leakage repair starts with finding where the water goes. Most leaks in a tiled pool are at a fitting or a joint, not through the middle of a wall. Those can be repaired locally, without stripping the pool.

How to stop a pool leak while water is flowing

Water running through a hole, crack or joint is stopped before any other work. A lining or grout applied over running water lifts at that spot.

Injection work is covered in full on the injection grouting page.

Repairing pool fittings, pipe sleeves, expansion joints and cracks

1. 1
   Lower the water and dry the area

   Drop the level below the leak, or drain the pool for work on the floor. Clean off scale, algae and all loose grout and mortar.Why: The area has to be dry, since repair materials do not bond to wet surfaces.
2. 2
   Pipe sleeves, lights and the main drain

   Rake out the gap around the fitting to sound material and pack it with non-shrink grout made with RAPIDSTRONG GROUT ADMIX. Where water is still coming through, stop it first with RAPIDSTRONG PLUG 31 or WONDERSEAL PLUG XL.Why: The gap round a fitting is the usual leak, and it is raked out and packed with a bonded material.
3. 3
   Expansion joints

   Cut out the old sealant, clean and dry the joint faces, prime with ROOFEXSEAL PRIMER PS / NPS and reseal with ROOFEX-SEAL PS. It is recommended for potable water-retaining structures, takes joints of 6 to 25 mm in a single application with the width twice the depth, and cures in 7 days at 20°C. Gun grade is used in wall joints and pour grade in floor joints.Why: The old sealant is cut out so that the new one bonds to sound, dry, primed faces.
4. 4
   Cracks in the shell

   Remove the tiles over the crack, open it to a V-groove, inject it if it leaks, and fill the groove with a putty of ROOFCOAT FLEXI 100 and cement. Coat the strip with the lining in two coats, with fibre mesh in the first coat, lapping onto the sound lining on each side.Why: The tiles are removed so that the crack can be opened, injected and filled.
5. 5
   Seeping shell: grout through drilled holes

   If the shell seeps or sweats through honeycombed or porous concrete, grout it through drilled holes before any lining goes on, so the water is stopped inside the concrete and the lining is not pushed off later. Drill 12 to 14 mm holes into the leaking zone, fix a rubber nozzle in each with cement and the accelerator RAPIDSTRONG QS 113, and pump cement slurry made with RAPIDSTRONG GROUT ADMIX (250 g per 50 kg of cement), RAPIDSTRONG GROUT PB 66 or ROOFEX GP at about 140 psi until the hole refuses more. Where water is running or gushing, cement would wash away, so inject RAPIDSTRONG GROUT PU instead, which reacts with the water and expands to block the flow. Then remove the nozzles and seal every hole flush with ROOFCRETE AR and cement. The six steps, with the reason for each, follow right below as steps 5a to 5f.Why: Seeping concrete is stopped inside the concrete first, and a lining over a seeping shell is pushed off.

Step 5 in detail: grout the seeping shell through drilled holes

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. 5a
   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. 5b
   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. 5c
   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. 5d
   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. 5e
   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. 5f
   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.

1. 6
   Retile and regrout the repaired strip

   Fix the tiles back in a full bed of adhesive and grout as in the tiling section.Why: The repaired strip is retiled in a full bed, so it matches and holds.
2. 7
   Cure, refill and watch the level

   Refill only after the repair has cured, then mark the level and record it daily.Why: The repair has to cure before water loads it, and the level shows whether it holds.

Pool tiles falling off or the shell leaking: strip, reline and retile

This is the extreme case, and it is the last resort. It is right when tiles sound hollow or are falling over large areas, when earlier local repairs have failed, or when the shell itself seeps through cracks and porous concrete. Local repair is tried first. When it cannot reach the problem, the pool is taken back to the shell and rebuilt in the right order.

1. 1
   Drain the pool and strip to the shell

   Remove the tiles, the old bed and any failed coating. Remove all loose, hollow and flaking plaster down to sound concrete.Why: The repair bonds to the sound shell, so failed tile, bed and coating all come off.
2. 2
   Check for groundwater

   If the empty shell is damp or water enters, plug and inject those points first with RAPIDSTRONG PLUG 31 and RAPIDSTRONG GROUT PU. Where groundwater is high, do not leave the pool empty longer than needed.Why: Groundwater pushing into an empty shell lifts any lining, so it is dealt with first.
3. 3
   Make the shell sound

   Inject leaking cracks and construction joints, rebuild honeycombed or damaged concrete with ROOFCRETE AR over ROOFBOND SBR 401, and grout every pipe sleeve with non-shrink grout made with RAPIDSTRONG GROUT ADMIX.Why: Cracks, joints and honeycombs are the leak paths, and they are repaired before relining.
4. 4
   Fill cracks, form the cove, reseal the joints

   V-groove and fill the cracks, form the cove at the floor and wall junction, and reseal the expansion joints with ROOFEX-SEAL PS over its primer.Why: The cracks are filled and the joints resealed, and the cove lets the lining turn the corner.
5. 5
   Reline in two coats

   Apply the lining chosen for the pool over the floor and walls, with fibre mesh bedded in the wet first coat at the junctions and over repairs.Why: Two coats with a mesh at the joints make a continuous waterproof skin.
6. 6
   Cure and water test

   Fill the pool and record the level daily. Do not tile until the shell holds water.Why: A slow leak shows over days, so the level is recorded before tiling.
7. 7
   Retile and grout

   Fix the tiles in a full bed of adhesive gauged for submerged work and grout with epoxy grout or latex-modified cement grout.Why: Submerged work needs an adhesive and grout made for it.
8. 8
   Wait, then fill

   Give the adhesive and grout their full cure before the pool is filled and dosed.Why: The adhesive and grout must reach their full cure before the water and the chemicals dose.

Best waterproofing for a swimming pool: comparing the Armstrong linings

The lining under the tiles is the main barrier in swimming pool waterproofing. Armstrong makes several that are listed for pools and water-retaining structures. Each is a sound choice. They differ in chemistry, in the pressure they are made for, so the reader can pick the one that fits the pool, and an Armstrong expert helps choose.

ROOFCRETE AR or ROOFCRETE AR 576: which repair mortar

The method is the same for both: cut back to sound concrete, saturate it to a saturated-surface-dry state, apply the bond coat (ROOFBOND SBR 401) and place the mortar into the tacky coat, compact, finish, then moist-cure for at least 7 days.

Pool shutter joints, cracks and planter boxes: the standard sequence

The shell of a pool or planter box leaks first at its shutter joints, cracks and seeping patches. These are closed one at a time and then the whole surface is coated, so the pool is sealed as one continuous, flexible shell. Doses, thicknesses and coats are the standard figures; the site and the exposure decide where they move.

1. 1
   Clean

   Clean the surface of dirt, dust and other contamination. For a planter box, remove the soil first.Why: The coating bonds to clean concrete only.
2. 2
   Shutter joints

   Seal the shutter joints with a polymer putty of ROOFBOND SBR 401 mixed with an equal quantity of water, then cement and fine sand.Why: Shutter joints are the cold joints where one pour met the next. The latex-modified putty bonds to old concrete and does not shrink away.
3. 3
   Cracks

   Cut a V-groove along each crack, prepare the surface and fill the crack with a putty of ROOFCOAT FLEXI 100 and cement.Why: The flexible putty keeps the crack sealed while it moves slightly.
4. 4
   Two coats

   Apply two coats of ROOFCOAT FLEXI 100, the acrylic polymer elastomeric cementitious coating, mixed with cement as the datasheet directs.Why: Two coats give a continuous, flexible waterproof skin over the whole surface.
5. 5
   Grout the shell if it seeps

   If the concrete itself seeps, grout through 12 to 14 mm holes as in the seeping-shell step above, using the rubber nozzles fixed with cement and quick-setting compound.Why: Seeping concrete lifts a coating laid over it, so it is stopped first.

Positive side and negative side in a swimming pool

Pool decks, balancing tanks and plant rooms follow their own pages: water tank waterproofing, balcony and podium waterproofing and basement waterproofing.

Swimming pool waterproofing chemicals and products by layer

How much waterproofing material for a 10 m by 5 m swimming pool

Approximate quantities for a pool 10 m long, 5 m wide and 1.5 m deep on average. The floor is 50 sq.m and the four walls are 45 sq.m, so 95 sq.m in all, or about 1,023 sq.ft. Figures are worked out from each product's stated coverage on a smooth, prepared surface. An Armstrong expert confirms the final quantity after seeing the site.

Standards and the water test for swimming pools

• IS 3370 is the Indian code for concrete structures that store liquids. Its water-tightness test: fill, let the structure stand, then record the level every 24 hours for 7 days.
• ROOFCOAT FLEXI 100 is tested to ASTM D412, ASTM C836 and ASTM D4541.
• ROOFBOND RFX PLUS 210 is tested to ASTM C836, ASTM D4541 and EN 1062-7, with no water penetration at a 50 m water head.
• ROOFCOAT PU 2K complies with EN 1062-3 and EN 1504-2, with nil chloride permeability to ASTM C 1202.
• ROOFEX 2K 711: hydrostatic resistance of 10 to 12 bar to ASTM D 5385.
• ROOFEX-SEAL PS complies with ASTM C-920-87, BS 4254-83, DIN 18549 and TT-S-00227E.
• TILEX 351 PLUS: ANSI A118.4, EN 12004 C2TE and IS 15477:2019 Type 2 T.
• CONPROOF LW 200 and CONPROOF 500 conform to IS 2645:2003. CONPROOF No. 1 is ISI marked to IS 2645.

Swimming pool waterproofing material calculator

Enter the pool size to see the lining, tile adhesive and grout needed for the floor and walls. Quantities only.

Eight mistakes that make a swimming pool leak

1. Treating tiles and grout as the waterproofing. They are the finish. The lining under them keeps the water in.
2. Tiling before the water test. A leak found after tiling means breaking tiles to reach it.
3. Leaving pipe sleeves and light niches ungrouted. Ordinary cement slurry shrinks and leaves a gap around every fitting.
4. Filling an expansion joint with mortar or tiling across it. The joint moves, the mortar cracks, and the tiles over it lift.
5. Fixing tiles on dabs of mortar. The voids fill with water and the tiles debond.
6. Using plain cement grout under water. It is porous and washes out. Use epoxy grout or a latex-modified cement grout.
7. Lining over loose plaster, algae or old flaking coating. The lining bonds to whatever is under it. Remove everything loose first.
8. Filling the pool too early. The lining, the adhesive and the grout each need their cure before they go under water.

Swimming pool waterproofing questions and answers