Pool Waterproofing Guide

A swimming pool constantly holds thousands of gallons of water against concrete, mortar, masonry, joints, penetrations, and interior finishes. Even a small crack, poorly sealed fitting, or weak construction joint can allow water to escape from the pool or enter the structure from the surrounding soil.

That is why pool waterproofing should be planned as a complete system rather than treated as a single coating applied over the visible surface.

Concrete and masonry may appear solid, but they contain pores and capillary pathways that can absorb and transmit moisture. Cinder block pools create additional concerns because the walls include multiple blocks, mortar joints, internal cells, and transitions that must all work together.

A dependable pool waterproofing system may include:

• Proper structural construction
• Integral waterproofing in new concrete or mortar
• Crack and joint treatments
• Waterstops
• Cementitious waterproofing
• A pool waterproofing membrane
• Compatible interior finishes
• Sealed plumbing penetrations
• Drainage around the outside of the pool
• Correct curing and water-filling procedures

The correct products depend on whether the pool is new or existing, built from poured concrete or concrete block, located above or below grade, and finished with plaster, tile, stone, or another material.

Rebotec USA supplies mineral-based waterproofing products for concrete and mortar used in residential, commercial, and industrial projects. For product information related to a concrete or masonry pool project, call Rebotec USA at +1 469-352-3379.

Before using any waterproofing product in a swimming pool, water feature, potable-water structure, or area exposed to animals, confirm that the product and complete system are approved for that specific use.

What Is Pool Waterproofing?

Pool waterproofing is the process of creating a continuous system that helps prevent water from passing through the pool shell, walls, floor, joints, fittings, and surrounding construction.

The system may need to resist water moving in two directions.

Water Moving Out of the Pool

Water inside the pool creates pressure against:

• Pool walls
• Pool floor
• Construction joints
• Drains
• Lights
• Skimmers
• Returns
• Plumbing penetrations
• Steps and benches

If any part of the pool shell or waterproofing system is incomplete, water may escape into the surrounding soil or building.

Water Moving Into the Pool Structure

Groundwater may also press against the outside of an in-ground pool.

This external pressure may affect the pool when it is:

• Empty
• Partially drained
• Located in wet soil
• Near a high water table
• Surrounded by poor drainage

Pool waterproofing should therefore consider both internal water containment and external groundwater conditions.

Is Concrete Naturally Waterproof?

Standard concrete is not completely waterproof.

Concrete contains:

• Microscopic pores
• Capillary pathways
• Construction joints
• Control joints
• Possible shrinkage cracks
• Tie holes
• Honeycombing
• Plumbing penetrations

Dense, well-consolidated, properly cured concrete may resist water better than poorly placed concrete, but it should not automatically be treated as a complete watertight system.

Concrete pool waterproofing may require protection:

• Within the concrete
• On the pool's interior surface
• At every joint and penetration
• On the exterior where groundwater is a concern

Why Pools Leak

A leaking pool does not always mean that water is passing through the open wall surface. Many leaks begin at joints, equipment, or penetrations.

Common causes include:

• Structural cracks
• Shrinkage cracks
• Failed construction joints
• Loose fittings
• Damaged plumbing
• Leaking skimmers
• Failed light niches
• Cracked drains
• Deteriorated sealant
• Failed tile grout
• Damaged plaster
• Poor waterproofing transitions
• Inadequate curing
• Movement between different materials

Water may also disappear because of evaporation or splash-out, so the source should be investigated before the pool surface is removed or coated.

Signs a Pool May Have a Waterproofing Problem

Possible warning signs include:

• Water level dropping faster than expected
• Damp soil around the pool
• Wet areas beneath an elevated pool
• Efflorescence on the outside of the pool wall
• Cracks in plaster or concrete
• Loose or hollow-sounding tile
• Rust stains
• Spalling concrete
• Damp equipment rooms
• Water stains around penetrations
• Repeated repair failure
• Water appearing in nearby structures

White mineral deposits on the outside of a concrete or masonry pool may indicate that water is passing through the material and depositing salts as it evaporates.

A professional leak test may be needed to determine whether the problem comes from the pool shell, plumbing, evaporation, or equipment.

Concrete Pool Waterproofing

Concrete pool waterproofing protects the shell from water passing through pores, cracks, joints, and penetrations.

A complete system may include:

1. Properly designed structural concrete
2. Correct concrete mix and placement
3. Integral waterproofing
4. Waterstops at construction joints
5. Crack repair
6. Surface preparation
7. Waterproofing membrane or coating
8. Reinforcement at corners and transitions
9. Compatible plaster, tile, or finish
10. Proper curing before filling

The waterproofing layer should remain continuous across the pool floor, walls, steps, benches, drains, lights, skimmers, and plumbing fittings.

New Concrete Pool Construction

New construction offers the best opportunity to plan waterproofing before the pool shell is placed.

Important considerations include:

• Structural design
• Soil conditions
• Groundwater
• Reinforcement
• Concrete mix design
• Construction-joint locations
• Waterstops
• Plumbing penetrations
• Concrete consolidation
• Curing
• Interior membrane
• Final finish

Rebotec Admix Powder is a mineral-based product designed to help create hydrophobic properties throughout compatible new concrete or mortar.

An integral waterproofing product may improve the water resistance of the cementitious material, but it does not replace:

• Structural engineering
• Reinforcement
• Waterstops
• Crack-control design
• Correct concrete placement
• Proper consolidation
• Curing
• Membranes when required
• Sealing around penetrations

Each part of the system must work together.

Existing Concrete Pool Waterproofing

An existing pool may need to be drained and inspected before repairs begin.

The project may include:

• Removing failed plaster
• Removing tile in damaged areas
• Cleaning the concrete
• Repairing cracks
• Treating rusted reinforcement
• Repairing spalled concrete
• Sealing penetrations
• Correcting hollow or weak areas
• Applying a waterproofing membrane
• Installing new plaster, tile, or another finish

A new surface should not be installed over loose, contaminated, cracked, or structurally unstable material.

How to Waterproof a Cinder Block Pool

Cinder block and concrete block pools require special attention because the walls contain many individual masonry units and mortar joints.

The blocks may also be hollow unless they are filled and reinforced as part of the pool's structural design.

A block wall should not be assumed capable of holding pool water simply because the visible surface has been plastered.

Step 1: Confirm the Pool Is Structurally Designed

A pool wall must resist the pressure of water inside the pool and the force of surrounding soil outside it.

The structure may require:

• Reinforcing steel
• Filled block cells
• Bond beams
• Proper footings
• Engineered wall thickness
• Connections between walls and floor
• Structural mortar or grout

Waterproofing products cannot make an inadequately constructed wall structurally safe.

Step 2: Inspect the Block and Mortar

Look for:

• Cracked blocks
• Open mortar joints
• Loose mortar
• Uneven wall sections
• Honeycombing
• Exposed reinforcement
• Failed patches
• Active water leaks
• Movement between the wall and floor

Damaged materials should be repaired before applying the waterproofing system.

Step 3: Fill Voids and Create a Continuous Surface

A rough cinder block wall may require a cementitious parging or rendering layer before the main membrane is applied.

This layer can help:

• Fill block texture
• Cover mortar joints
• Create a smoother surface
• Eliminate low spots
• Provide a continuous substrate
• Improve membrane coverage

The parging material should be compatible with the block, mortar, and waterproofing system.

Step 4: Treat the Wall-to-Floor Joint

The joint where the block wall meets the pool floor is a common leak location.

This transition may require:

• Waterstop
• Flexible sealant
• Cementitious cove
• Reinforcing fabric
• Additional membrane thickness
• Compatible joint treatment

A rigid coating applied over an active or poorly constructed joint may crack.

Step 5: Repair Cracks and Mortar Joints

Cracks should be evaluated to determine whether they are stable or moving.

Possible repair materials include:

• Cementitious repair mortar
• Flexible sealant
• Injection resin
• Hydraulic repair material
• Reinforcing mesh
• Compatible pool patching products

Structural or recurring cracks should be evaluated before waterproofing.

Step 6: Detail Plumbing Penetrations

Seal around:

• Main drains
• Return fittings
• Skimmers
• Lights
• Suction fittings
• Overflow pipes
• Cleaning-system fittings

The waterproofing membrane should connect continuously to each fitting or approved flange.

Step 7: Apply the Pool Waterproofing Membrane

The selected membrane should be approved for:

• Continuous immersion
• Pool chemicals
• The chosen substrate
• The planned finish
• Positive-side water pressure
• Expected movement
• Interior pool use

Apply it at the specified thickness and number of coats.

Step 8: Install the Compatible Pool Finish

Possible finishes include:

• Pool plaster
• Tile
• Stone
• Specialty pool coatings
• Other approved systems

The finish and setting materials must be compatible with the waterproofing membrane.

Step 9: Cure the Complete System

The pool should not be filled until repair materials, membranes, adhesives, grout, plaster, and finishes have cured as required.

Filling too early may cause:

• Soft material
• Discoloration
• Poor adhesion
• Blistering
• Washout
• Reduced performance

Pool Waterproofing Membrane

A pool waterproofing membrane creates a continuous barrier across the interior shell.

Membranes may be:

• Cementitious
• Flexible cementitious
• Liquid applied
• Sheet applied
• Polyurethane based
• Epoxy based
• Mineral based
• Polymer modified

Not every general waterproofing product is suitable for a swimming pool.

A pool membrane may need to tolerate:

• Continuous immersion
• Chlorinated or treated water
• Temperature changes
• Cleaning
• Water pressure
• Tile-setting materials
• Plaster
• Movement at joints
• Long curing periods

Always confirm the product's approval for the exact application.

Cementitious Pool Waterproofing Membrane

Cementitious membranes are commonly used over concrete and masonry because they bond well to compatible cement-based substrates.

Potential benefits include:

• Strong concrete compatibility
• Ability to fill surface pores
• Application to some damp surfaces
• Compatibility with selected tile systems
• Mineral or cement-based construction

Some cementitious membranes are rigid. Others include polymers to provide additional flexibility.

Rigid materials may crack if the pool shell moves.

Liquid-Applied Pool Membrane

A liquid-applied membrane may be brushed, rolled, sprayed, or troweled onto the surface.

Potential advantages include:

• Fewer seams
• Coverage over complex shapes
• Easier detailing around some fittings
• Continuous protection over steps and benches

Potential limitations include:

• Field-controlled thickness
• Pinholes
• Missed areas
• Uneven application
• Strict cure requirements
• Possible sensitivity to substrate moisture

Sheet Pool Membrane

Sheet membranes may provide consistent factory-controlled thickness.

However, the installer must carefully treat:

• Seams
• Corners
• Drains
• Fittings
• Steps
• Benches
• Curved surfaces
• Terminations

The sheet membrane and all adhesives or tapes should be approved for continuous pool immersion.

Concrete Pool Waterproofing Products

Concrete pool waterproofing products can serve different purposes within the system.

They may include:

• Integral concrete admixtures
• Waterstops
• Crack-repair materials
• Injection resins
• Cementitious membranes
• Mineral-based coatings
• Flexible liquid membranes
• Sheet membranes
• Joint sealants
• Tile adhesives
• Pool plaster
• Protective finishes

The best product depends on:

• New or existing construction
• Pool material
• Water pressure
• Groundwater
• Surface condition
• Structural movement
• Finish material
• Chemical exposure
• Interior or exterior application

A product that works on an exterior basement wall is not automatically appropriate for continuous pool immersion.

Integral Waterproofing Products

Integral waterproofing is mixed into fresh concrete, mortar, grout, or compatible repair material.

Potential benefits include:

• Protection throughout the cementitious material
• Reduced dependence on a single surface layer
• Water resistance in new concrete or mortar
• No surface film to peel in the same manner as paint
• Support for complex concrete shapes

Rebotec Admix Powder may be considered for compatible new concrete, mortar, grout, parging, or cementitious repairs.

Project specifications and product approval should be confirmed before use in a pool or continuously immersed structure.

Surface-Applied Mineral Waterproofing

Rebotec Paint is a surface-applied mineral-based hydrophobic waterproofing product for compatible concrete and masonry.

For swimming pools, water features, tanks, and continuous immersion, verify suitability, approvals, finish compatibility, water chemistry requirements, and curing instructions before selection.

Pool Waterproofing Details That Matter

The waterproofing system is often most vulnerable at transitions and penetrations.

Wall-to-Floor Joint

This joint may experience movement and concentrated stress.

Possible details include:

• Waterstop
• Flexible sealant
• Reinforced cove
• Additional membrane
• Designed construction-joint treatment

Inside and Outside Corners

Corners may require reinforcing fabric or additional membrane layers to reduce stress concentration.

Main Drains

The membrane must connect continuously to the drain assembly.

A drain leak may be caused by:

• Cracked fitting
• Loose flange
• Failed sealant
• Broken plumbing
• Membrane stopping short
• Movement around the drain

Skimmers

Skimmers connect the pool shell to plumbing and may be surrounded by different materials.

The waterproofing transition should remain continuous around the skimmer body and adjacent concrete.

Pool Lights

Light niches and conduit penetrations can leak when seals, fittings, or transitions fail.

Electrical pool components should be handled by qualified professionals and installed according to applicable safety requirements.

Return and Suction Fittings

All fittings should be securely installed and integrated into the waterproofing system.

Steps and Benches

Steps and benches create numerous corners, edges, and transitions that need complete membrane coverage.

Expansion and Construction Joints

Joints should be treated according to expected movement.

A rigid patch should not be used where a flexible joint system is required.

Positive-Side and Negative-Side Pool Waterproofing

Positive-side waterproofing is installed on the side that directly faces the water.

For a pool, this is generally the interior surface.

Potential benefits include:

• Stops water before it enters the pool shell
• Protects the structural concrete
• Covers repaired cracks and pores
• Integrates with fittings and drains
• Supports tile or plaster systems

Negative-side waterproofing is applied to the outside of the shell or to the dry side after water has entered the concrete.

Exterior waterproofing may be useful for resisting groundwater, but it does not replace a complete interior containment system when one is required.

A pool may need both interior and exterior water management depending on site conditions.

Groundwater Around In-Ground Pools

Groundwater may create pressure outside an in-ground pool.

This can be especially important when the pool is emptied.

Potential concerns include:

• Water entering cracks
• Dampness behind the membrane
• Exterior pressure on the shell
• Pool movement or uplift
• Coating failure
• Saturated soil
• Drainage problems

The pool may require:

• Site drainage
• Hydrostatic relief
• Exterior waterproofing
• Drainage stone
• Perimeter drains
• Sump or dewatering systems

A pool should not be drained without understanding groundwater conditions and the structural design.

How to Waterproof a Concrete Pool

A general concrete pool waterproofing process may include the following steps.

Step 1: Investigate the Leak

Determine whether water loss comes from:

• Evaporation
• Plumbing
• Skimmers
• Drains
• Fittings
• Cracks
• Pool shell
• Equipment
• Overflow systems

Do not assume the visible crack is the only leak source.

Step 2: Drain the Pool Safely

Consider groundwater, structural conditions, finish requirements, and applicable professional guidance before draining.

Step 3: Inspect the Pool Shell

Look for:

• Cracks
• Spalling
• Rust stains
• Loose plaster
• Hollow tile
• Failed joints
• Exposed reinforcement
• Damaged fittings
• Efflorescence
• Previous repairs

Step 4: Remove Failed Materials

Remove:

• Loose plaster
• Delaminated coatings
• Weak concrete
• Failed sealant
• Damaged tile
• Unstable patches
• Contamination

Step 5: Repair the Structure

Repairs may include:

• Crack injection
• Concrete patching
• Reinforcement treatment
• Joint repair
• Mortar replacement
• Rebuilding damaged areas
• Repairing or replacing fittings

Structural repairs should be completed before surface waterproofing.

Step 6: Prepare the Surface

Preparation may involve:

• Grinding
• Abrasive blasting
• Pressure washing
• Cleaning
• Vacuuming
• Removing laitance
• Creating the required surface profile

The substrate should be clean, sound, and compatible with the membrane.

Step 7: Detail Joints and Penetrations

Apply approved sealants, reinforcement, collars, waterstops, or additional membrane around critical details.

Step 8: Apply Primer if Required

The primer should be approved for the substrate, membrane, and immersion conditions.

Step 9: Install the Main Waterproofing Membrane

Follow the required:

• Coverage rate
• Wet-film thickness
• Dry-film thickness
• Number of coats
• Recoat interval
• Temperature
• Surface-moisture condition
• Cure time

Step 10: Inspect and Test

Look for:

• Pinholes
• Gaps
• Thin areas
• Open seams
• Incomplete fitting details
• Poor corner coverage
• Damage

Testing methods depend on the pool system and project.

Step 11: Install the Interior Finish

The finish should be compatible with the membrane and applied according to the complete system requirements.

Step 12: Allow Proper Curing and Fill the Pool

Follow the specified schedule for filling and balancing the pool water.

Some finishes require the pool to be filled continuously once filling begins.

Waterproofing a Pool Before Tile

Tile is a finish, not usually the primary waterproofing barrier.

Water can pass through:

• Grout
• Small cracks
• Joints
• Failed adhesive
• Corners
• Penetrations

A pool designed for tile may require:

1. Sound concrete or masonry substrate
2. Repairs and surface preparation
3. Pool waterproofing membrane
4. Approved tile-setting mortar
5. Compatible grout
6. Flexible movement joints
7. Proper curing

The membrane, adhesive, grout, and sealants should be approved as a compatible system.

Common Pool Waterproofing Mistakes

Avoid these common errors:

• Assuming concrete is naturally waterproof
• Waterproofing before repairing structural cracks
• Applying products over loose plaster
• Ignoring block mortar joints
• Skipping the wall-to-floor transition
• Failing to seal plumbing penetrations
• Using ordinary exterior paint inside a pool
• Selecting a product not approved for immersion
• Applying the membrane too thin
• Leaving pinholes
• Mixing incompatible products
• Installing tile before curing
• Filling the pool too early
• Ignoring groundwater
• Assuming tile and grout are waterproof
• Draining a pool without considering external water pressure

Pool Waterproofing Maintenance

Routine inspection can help identify problems before they become larger leaks.

Check for:

• Cracked tile or grout
• Damaged sealant
• Rust stains
• Unusual water loss
• Loose fittings
• Cracks in plaster
• Efflorescence
• Damp areas outside the pool
• Failed expansion joints
• Spalling concrete

The pool's water chemistry should also be properly maintained because unbalanced water may affect certain finishes, grouts, metals, and cementitious surfaces.

When Pool Waterproofing Is Not Enough

A coating or membrane alone may not solve:

• Major structural cracks
• Bowing block walls
• Pool settlement
• Extensive reinforcing-steel corrosion
• Failed plumbing
• Severe groundwater pressure
• Inadequately reinforced masonry
• Unsafe pool walls
• Significant shell movement
• Damaged drains or fittings

These conditions may require engineering, plumbing repair, structural reconstruction, drainage improvements, or replacement of damaged components.

Get Help Choosing Concrete Pool Waterproofing Products

Choosing among pool waterproofing products, integral additives, cementitious coatings, mineral-based products, liquid membranes, sheet membranes, and joint treatments can be difficult.

The correct solution must match the pool structure, finish, water pressure, chemical exposure, groundwater, and local project requirements.

Rebotec USA helps contractors, builders, distributors, engineers, and property owners evaluate mineral-based waterproofing products for concrete and mortar.

Rebotec products may be considered for compatible:

• New concrete pool shells
• Concrete repairs
• Mortar
• Block-wall parging
• Cementitious pool components
• Water features
• Tanks
• Other water-exposed concrete or masonry

Before using any product in a swimming pool or continuously immersed structure, confirm the product's approval and compatibility with the full pool system.

Call Rebotec USA at +1 469-352-3379 for product information and application guidance.

Conclusion

Pool waterproofing protects concrete, cinder block, mortar, joints, fittings, and surrounding construction from water intrusion and leakage.

Concrete is durable but not automatically waterproof. A concrete pool may require integral waterproofing, crack and joint repair, waterstops, a pool waterproofing membrane, sealed penetrations, and a compatible interior finish.

Cinder block pools require careful structural construction because the walls contain multiple blocks, mortar joints, and often hollow cells. The block wall may need reinforcement, filled cells, parging, joint treatment, and a continuous membrane before the final pool finish is installed.

A pool waterproofing membrane must be rated for continuous immersion, water pressure, pool chemicals, and the selected plaster or tile system. Ordinary exterior paint or a general-purpose basement coating should not automatically be used inside a pool.

Critical pool waterproofing details include wall-to-floor joints, drains, skimmers, lights, returns, suction fittings, steps, benches, corners, and construction joints.

Groundwater outside the pool should also be evaluated, especially before an in-ground pool is drained.

For new construction, integral waterproofing can improve water resistance throughout the concrete or mortar. It does not replace structural engineering, waterstops, reinforcement, placement, curing, membranes, or penetration details when those elements are required.

For help evaluating a mineral-based waterproofing product for concrete or mortar, call Rebotec USA at +1 469-352-3379.

FAQs About Pool Waterproofing

What is pool waterproofing?

Pool waterproofing is the process of creating continuous protection that helps prevent water from passing through the pool walls, floor, joints, and penetrations.

Does a concrete pool need waterproofing?

Yes. Standard concrete contains pores and may develop cracks, joints, voids, and penetrations that allow water to pass through.

What is concrete pool waterproofing?

Concrete pool waterproofing combines structural construction, integral protection, repairs, joint treatments, membranes, and compatible finishes to create a watertight pool shell.

What are common pool waterproofing products?

Common products include integral admixtures, waterstops, crack-repair materials, cementitious membranes, flexible liquid membranes, mineral-based coatings, sheet membranes, and joint sealants.

What is a pool waterproofing membrane?

It is a continuous liquid- or sheet-applied barrier installed over the pool shell to help prevent water from entering or escaping through the concrete or masonry.

Is tile enough to waterproof a pool?

No. Tile and grout are not normally the complete waterproofing system. A compatible membrane is generally required beneath the finish.

How do you waterproof a cinder block pool?

The wall should be structurally reinforced, repaired, parged or rendered as needed, detailed at joints and penetrations, and covered with a compatible immersion-rated membrane and finish.

Can cinder block hold pool water?

A properly designed, reinforced, filled, and waterproofed concrete block structure may be used for a pool. Unreinforced or hollow block walls should not be assumed capable of handling pool pressure.

Does a block pool need parging before waterproofing?

It may. Parging can fill surface texture, cover mortar joints, and create a more continuous substrate for the membrane.

How do you waterproof the joint between a pool wall and floor?

The joint may require a waterstop, flexible sealant, reinforced cove, additional membrane, or another engineered detail.

Can pool waterproofing be applied over old plaster?

Only when the existing plaster is sound, securely bonded, clean, and compatible. Loose or hollow plaster should be removed.

Can ordinary waterproof paint be used in a swimming pool?

Not unless it is specifically approved for continuous immersion, pool chemicals, the substrate, and the planned finish.

What is the best concrete pool waterproofing product?

The best product depends on the pool design, concrete condition, water pressure, finish, movement, groundwater, and applicable approvals.

Can integral waterproofing be used in a concrete pool?

Yes, when the product and project specifications support the application. Integral treatment is generally added to new concrete, mortar, grout, or repairs.

Does integral waterproofing replace a pool membrane?

Not necessarily. Surface membranes, waterstops, joint treatments, penetrations, and compatible finishes may still be required.

Can a leaking pool be waterproofed from the outside?

Exterior waterproofing may help manage groundwater or exterior moisture, but leakage from the pool interior usually requires positive-side repairs and waterproofing.

Why is my pool losing water?

Possible causes include evaporation, plumbing leaks, damaged fittings, skimmers, drains, cracks, failed joints, or a leaking pool shell.

How can I tell whether my pool is leaking or evaporating?

Water-level testing and professional leak detection can help distinguish ordinary evaporation from a plumbing or structural leak.

Can pool cracks be covered with waterproofing?

Cracks should be evaluated and repaired before the membrane is applied. Moving or structural cracks may require specialized treatment.

How thick should a pool waterproofing membrane be?

The required thickness varies by product. Follow the specified coverage rate and wet- or dry-film thickness rather than estimating visually.

How long should pool waterproofing cure before filling?

Cure time depends on the repair materials, membrane, adhesive, grout, finish, temperature, and humidity. Follow the complete system instructions.

Can waterproofing stop groundwater from entering an empty pool?

Exterior drainage, hydrostatic relief, and outside waterproofing may be needed. Interior coating alone may not address significant external pressure.

Should a pool be drained to repair waterproofing?

Many repairs require draining, but groundwater and structural conditions should be evaluated before an in-ground pool is emptied.

Who can help me choose concrete pool waterproofing products?

Rebotec USA can help evaluate mineral-based waterproofing products for concrete and mortar. Call +1 469-352-3379 for product and application guidance.