Brick Foundation and Retaining Wall Waterproofing

Brick foundations and retaining walls are designed to support heavy loads and withstand years of exposure. However, brick, mortar, concrete, and concrete block are not naturally waterproof.

These materials contain pores that can absorb moisture. Walls also include mortar joints, cracks, drainage openings, construction joints, penetrations, and transitions where water may enter.

For a brick foundation, moisture may travel through the brick or damaged mortar and reach a basement, crawl space, or interior wall. For a retaining wall, water can collect in the soil behind the structure and create pressure that contributes to leaks, staining, movement, cracking, or failure.

Effective waterproofing must address both the wall and the water around it.

A coating or sealer may reduce absorption, but retaining wall waterproofing usually also depends on drainage. Without a way for water to escape, saturated soil can continue pushing against the wall and waterproofing system.

Rebotec USA supplies mineral-based waterproofing products for concrete and mortar used in residential, commercial, and industrial projects. For help choosing a product for waterproofing a brick foundation, concrete retaining wall, mortar repair, or related application, call Rebotec USA at +1 469-352-3379.

Why Brick Foundations and Retaining Walls Need Waterproofing

Brick and concrete walls often remain in contact with soil or are exposed to rain for long periods.

Water can enter through:

• Porous brick faces
• Mortar joints
• Cracks
• Wall caps
• Construction joints
• Pipe penetrations
• Wall-to-footing connections
• Concrete pores
• Honeycombed areas
• Damaged coatings
• Failed flashing
• Open wall transitions

A retaining wall faces an additional challenge: water may collect behind it.

When soil becomes saturated, the water increases the pressure placed against the wall. This pressure can push moisture through the masonry and may also increase the structural load on the wall.

Possible results include:

• Efflorescence
• Water stains
• Damp basement walls
• Peeling paint
• Mortar deterioration
• Spalling brick or concrete
• Mold-friendly conditions
• Rust on embedded metal
• Cracking
• Bowing
• Leaning
• Soil erosion
• Water flowing through joints
• Reduced wall service life

Waterproofing helps reduce water penetration, while drainage helps reduce the amount of pressure acting against the wall.

Is Brick Waterproof?

No. Brick is not automatically waterproof.

Some dense brick absorbs relatively little water, while older, softer, or more porous brick may absorb significantly more. Mortar joints are also common entry points, especially when they are cracked, recessed, loose, or missing.

Brick foundation moisture problems may be caused by:

• Porous masonry
• Deteriorated mortar
• Failed exterior coatings
• Groundwater
• Poor grading
• Short downspouts
• Clogged gutters
• Missing foundation drainage
• Cracks or settlement
• Water entering from the top of the wall

Applying a sealer without repairing the mortar or correcting drainage may provide incomplete protection.

Is a Retaining Wall Waterproof?

A retaining wall is not automatically waterproof simply because it is made from concrete, block, or masonry.

Retaining walls are designed primarily to hold back soil. Water management must usually be included separately through:

• Waterproofing or dampproofing
• Drainage aggregate
• Perforated drainpipe
• Filter fabric
• Weep holes
• Drainage board
• Proper wall caps
• Surface grading

A wall may appear dry during normal weather but begin leaking or staining after heavy rain because the soil behind it becomes saturated.

Waterproofing Brick Foundations

Waterproofing brick foundation walls requires careful treatment of the brick, mortar, cracks, and drainage around the structure.

For below-grade foundations, exterior positive-side waterproofing is often the most complete approach because it stops water before it enters the brick or mortar.

Signs a Brick Foundation Needs Waterproofing

Common warning signs include:

• Damp basement or crawl-space walls
• White mineral deposits
• Peeling interior paint
• Musty odors
• Mold or mildew
• Crumbling mortar
• Wet corners after rain
• Water around utility penetrations
• Dark brick or mortar
• Rust stains
• Spalling brick
• Stair-step cracks
• Water at the wall-to-floor joint

White powder on brick or mortar is often efflorescence. It forms when water moves through the masonry, carries salts to the surface, and evaporates.

Efflorescence should be cleaned, but the moisture source must also be corrected.

Exterior Brick Foundation Waterproofing

Exterior waterproofing is installed on the soil-facing side of the foundation.

A typical process may include:

1. Inspecting the foundation and drainage
2. Excavating the affected wall
3. Cleaning the brick and mortar
4. Repointing damaged joints
5. Repairing cracks and openings
6. Applying a parge coat when appropriate
7. Installing a waterproofing coating or membrane
8. Adding drainage or protection board
9. Inspecting the foundation drain
10. Backfilling carefully
11. Restoring the correct soil grade

The selected waterproofing system must be compatible with the brick, mortar, parging, and expected water exposure.

Why Parging May Be Needed

A brick or block foundation can have an uneven surface with recessed mortar joints and irregular masonry units.

Parging involves applying a cement-based layer over the wall. It may:

• Create a smoother surface
• Fill minor irregularities
• Cover mortar joints
• Provide a more uniform membrane substrate
• Reduce sharp edges
• Improve continuous coating coverage

Parging is not a substitute for structural repair or proper repointing. Loose and deteriorated mortar should be corrected first.

Interior Brick Foundation Waterproofing

Interior coatings may help reduce light dampness when exterior excavation is impractical.

Possible interior methods include:

• Cementitious coatings
• Mineral-based waterproofing products
• Masonry waterproofing paint
• Crack and mortar repair
• Wall drainage panels
• Interior perimeter drains
• Sump pumps
• Dehumidification

Interior products must be suitable for the direction of water pressure they will face.

When water enters from outside and pushes through the wall, it creates negative-side pressure against an interior coating. Ordinary paint may blister, peel, or separate under these conditions.

Interior waterproofing may manage the symptoms, but it does not always prevent water from entering and remaining inside the masonry.

Repointing Brick Before Waterproofing

Repointing is the process of removing deteriorated mortar and replacing it with compatible new mortar.

Repointing may be necessary when joints are:

• Cracked
• Missing
• Loose
• Deeply recessed
• Soft
• Washed out
• Separated from the brick

The replacement mortar should be compatible with the existing brick and masonry assembly.

Mortar that is too hard for older or softer brick can concentrate stress and contribute to brick damage.

Waterproofing should not be applied over loose or failing mortar.

Retaining Wall Waterproofing

Retaining wall waterproofing protects the soil-facing side of the wall from water and damp soil.

The system may be used with:

• Poured concrete retaining walls
• Concrete block retaining walls
• Brick retaining walls
• Masonry retaining walls
• Reinforced walls
• Basement walls that also retain soil
• Commercial landscape structures

The most effective time to waterproof a retaining wall is during construction, before the wall is backfilled.

Existing retaining walls may also be waterproofed, but excavation may be required to expose the back of the wall.

Why Drainage Matters Behind Retaining Walls

Water adds weight to the soil and creates pressure against the wall.

Without drainage, a retaining wall may experience:

• Constant dampness
• Water flowing through joints
• Efflorescence
• Freeze-thaw damage
• Staining
• Increased lateral pressure
• Cracking
• Bowing
• Leaning
• Soil washout
• Foundation movement

Waterproofing helps stop moisture from passing through the wall. Drainage reduces the water pressure behind it.

A complete system often needs both.

Retaining Wall Waterproofing Products

Retaining wall waterproofing products may include:

• Liquid-applied membranes
• Sheet membranes
• Cementitious coatings
• Rubberized coatings
• Mineral-based waterproofing products
• Asphalt-based coatings
• Drainage board
• Protection board
• Bentonite products
• Joint sealants
• Waterstops
• Integral concrete additives

The best product depends on:

• Wall material
• Soil conditions
• Groundwater
• Wall height
• Structural movement
• Drainage design
• Interior or exterior exposure
• Accessibility
• Required service life

Liquid-Applied Retaining Wall Membranes

Liquid membranes are brushed, rolled, sprayed, or troweled onto the prepared wall.

Once cured, they form a continuous protective layer.

Potential advantages include:

• Seamless coverage
• Conforms to irregular surfaces
• Easier detailing around some penetrations
• Can cover complex wall shapes
• Flexible product options

Potential limitations include:

• Field-controlled thickness
• Pinholes
• Missed areas
• Weather-sensitive installation
• Possible primer requirements
• Need for curing
• Vulnerability during backfilling

The required thickness should be followed carefully. Stretching the material too thin may reduce performance.

Sheet Waterproofing Membranes

Sheet membranes are manufactured in rolls or panels and installed over the wall.

Potential advantages include:

• Consistent thickness
• Strong liquid-water barrier
• Visible coverage
• Use in demanding below-grade conditions

Potential weaknesses include:

• Seams
• Overlaps
• Corners
• Wrinkles
• Terminations
• Penetrations
• Punctures

Sheet membrane seams must be installed according to the complete system requirements.

Cementitious Waterproofing

Cementitious coatings are made from cement-based materials and selected additives.

They generally bond well to:

• Poured concrete
• Concrete block
• Mortar
• Brick
• Parging
• Other cementitious surfaces

Some cementitious products are rigid, while others are polymer modified for more flexibility.

Rigid coatings may crack when a retaining wall moves. Expansion joints, construction joints, and structural cracks require separate detailing.

Mineral-Based Waterproofing Products

Mineral-based waterproofing products are designed for compatibility with concrete and mortar.

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

Rebotec Admix Powder can be added to new concrete, mortar, grout, or compatible repair materials to create hydrophobic properties throughout the cementitious material.

These products may be considered for:

• Concrete retaining walls
• New masonry
• Brick foundation repairs
• Mortar
• Parging
• Foundation walls
• Concrete repairs
• Commercial structures

The right product depends on whether the wall is new or existing and on the project's expected water exposure.

Concrete Retaining Wall Waterproofing

Concrete retaining walls may be poured in place, precast, or constructed from concrete masonry units.

Although poured concrete has fewer joints than masonry block, it may still contain:

• Shrinkage cracks
• Construction joints
• Form-tie holes
• Honeycombing
• Wall-to-footing transitions
• Pipe or drain penetrations
• Surface voids

Concrete retaining wall waterproofing should address these details before the main coating or membrane is installed.

Waterproofing New Concrete Retaining Walls

A new wall may include:

• Integral waterproofing additive
• Waterstops at construction joints
• Proper concrete consolidation
• Crack-control reinforcement
• Exterior waterproofing membrane
• Protection board
• Drainage board
• Perforated drainpipe
• Drainage aggregate
• Filter fabric
• Weep holes when appropriate
• Properly compacted backfill

Planning the full system before concrete placement makes it easier to create continuous protection.

Waterproofing Existing Concrete Retaining Walls

An existing wall may need to be excavated from behind.

The process may include:

1. Removing soil carefully
2. Cleaning the concrete
3. Repairing cracks and voids
4. Sealing penetrations
5. Applying a waterproof membrane
6. Installing drainage or protection board
7. Repairing or adding drainage
8. Backfilling with suitable material
9. Restoring surface grading

If the wall is already leaning, bowing, or heavily cracked, structural evaluation may be required before waterproofing.

Retaining Wall Drainage Systems

Drainage is one of the most important parts of a retaining wall system.

Perforated Drainpipe

A perforated pipe is commonly installed near the base of the wall to collect and redirect water.

It should discharge to:

• A safe gravity outlet
• A drainage system
• A sump system
• Another approved location

The outlet should not return water to the back of the wall.

Drainage Aggregate

Free-draining stone or gravel can provide space for water to move downward toward the drainpipe.

Fine soil placed directly against the wall may retain more water and increase pressure.

Filter Fabric

Filter fabric can help prevent fine soil from clogging the drainage aggregate or pipe.

The complete detail should allow water to enter the drainage system without allowing soil to wash away.

Drainage Board

Drainage board is installed against the waterproofing system and provides a vertical pathway for water.

It can also protect the waterproofing layer from some backfill damage.

Weep Holes

Weep holes allow trapped water to escape through the wall.

They may be used in certain masonry or retaining wall designs, but they should not be treated as the only drainage method for every wall.

Weep holes can clog and may leave visible staining on the wall face.

Waterproofing Brick Retaining Walls

Brick retaining walls combine the moisture concerns of masonry with the structural pressures of retained soil.

Water may enter through:

• Brick faces
• Mortar joints
• Wall caps
• Cracks
• The back of the wall
• Open drainage points
• Failed flashing

A brick retaining wall may require:

• Mortar repointing
• Cap repair
• Structural repair
• Back-side waterproofing
• Drainage board
• Drainpipe
• Free-draining aggregate
• Surface grading

Applying a clear sealer only to the visible face may reduce rain absorption, but it will not stop water collecting behind the wall.

The soil-facing side should be evaluated whenever possible.

Positive-Side vs Negative-Side Waterproofing

Positive-side waterproofing is installed where water first contacts the wall.

For a brick foundation or retaining wall, this is usually the exterior or soil-facing side.

Benefits include:

• Stops water before it enters the masonry
• Protects the wall material
• Covers repaired cracks and joints
• Works with drainage
• Reduces moisture inside the structure

Negative-side waterproofing is applied to the opposite face, such as the interior basement wall or visible front of a retaining wall.

Negative-side coatings may help with certain conditions, but water can still enter and remain within the wall.

For retaining walls, waterproofing only the visible face may trap moisture inside the masonry or fail to address pressure from behind.

How to Waterproof a Brick Foundation or Retaining Wall

The exact process varies, but the following steps provide a general overview.

Step 1: Identify the Water Source

Determine whether moisture comes from:

• Rain
• Groundwater
• Irrigation
• Poor grading
• Roof runoff
• Saturated backfill
• Cracks
• Mortar joints
• Failed drainage
• Plumbing

Step 2: Inspect the Wall

Look for:

• Loose mortar
• Cracks
• Bowing
• Leaning
• Efflorescence
• Spalling
• Open joints
• Failed coatings
• Water stains
• Missing caps
• Active leaks

Structural movement should be evaluated before waterproofing.

Step 3: Correct Surface-Water Problems

Possible improvements include:

• Cleaning gutters
• Extending downspouts
• Correcting grading
• Redirecting irrigation
• Repairing wall caps
• Installing surface drains
• Preventing water from flowing over the wall

Step 4: Expose the Soil-Facing Side

Existing foundation and retaining walls may require excavation.

Excavation must account for utilities, soil stability, nearby structures, wall support, and worker safety.

Step 5: Clean and Repair the Wall

Remove soil, loose mortar, failed coatings, and weak materials.

Repair cracks, joints, penetrations, voids, and damaged masonry with compatible materials.

Step 6: Apply Parging or Primer if Required

A parge coat may create a smoother surface. Some membranes also need a compatible primer.

Follow the complete system's preparation instructions.

Step 7: Install the Waterproofing Product

Apply the coating or membrane at the specified:

• Thickness
• Coverage rate
• Number of coats
• Overlap
• Temperature
• Surface-moisture condition
• Cure time

Pay close attention to corners, footing transitions, joints, wall caps, and penetrations.

Step 8: Install Drainage and Protection

Add the required:

• Protection board
• Drainage board
• Drainpipe
• Drainage stone
• Filter fabric
• Weep or outlet details

Step 9: Inspect the System

Check for:

• Gaps
• Thin spots
• Pinholes
• Punctures
• Failed seams
• Unsealed penetrations
• Incomplete transitions
• Drainage problems

Step 10: Backfill Carefully

Backfill should not damage the membrane or overload the wall.

Suitable drainage material should be installed where required by the wall design.

Common Waterproofing Mistakes

Avoid these frequent errors:

• Waterproofing only the visible wet spot
• Ignoring deteriorated mortar
• Coating over efflorescence
• Applying products to dirty walls
• Failing to repair cracks
• Using an above-grade sealer below ground
• Waterproofing the front of a retaining wall while ignoring the back
• Applying liquid membrane too thin
• Leaving sheet-membrane seams open
• Skipping protection board
• Backfilling before the coating cures
• Omitting drainage
• Allowing drain outlets to clog
• Ignoring wall caps
• Covering structural movement with paint

Waterproofing performs best when the wall, drainage, and surrounding site are treated as one system.

How to Choose the Best Waterproofing Product

Consider these factors before selecting a product.

Wall Material

Brick, concrete block, poured concrete, stone, and mortar may need different preparation and products.

Water Exposure

Occasional rain is different from groundwater or saturated soil.

Structural Movement

Flexible membranes may tolerate limited movement, but they do not repair an unstable wall.

Interior or Exterior Application

Products must be approved for the side and environment where they will be installed.

Above- or Below-Grade Use

Below-grade products must tolerate soil contact and expected water pressure.

Drainage Design

The coating or membrane should work with the drainpipe, drainage board, gravel, and backfill.

Existing Coatings

Old tar, paint, sealers, or unidentified materials may interfere with adhesion.

New or Existing Construction

New concrete and mortar can include an integral waterproofing product. Existing walls typically require surface preparation, repairs, coatings, and drainage work.

When to Contact a Professional

Professional evaluation is recommended when there is:

• A leaning or bowing retaining wall
• Large horizontal cracks
• Significant stair-step cracking
• Repeated basement leaks
• High groundwater
• Deep excavation
• Severe mortar deterioration
• Soil erosion
• Commercial retaining walls
• Water entering through several locations
• An unclear drainage outlet
• Structural movement

Waterproofing should not be used to hide a wall that is structurally unsafe.

Get Help Choosing a Waterproofing Product

Choosing among retaining wall waterproofing products, mineral-based coatings, membranes, sealers, integral additives, and drainage systems can be difficult.

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

Call Rebotec USA at +1 469-352-3379 for product information, application guidance, and help choosing a waterproofing solution for a brick foundation, concrete retaining wall, mortar repair, or related project.

Conclusion

Brick foundations and retaining walls require protection from both moisture and water pressure.

Brick foundation waterproofing may include mortar repair, parging, an exterior waterproofing coating or membrane, foundation drainage, and correct grading. Interior coatings can help with some dampness problems, but they may not prevent water from entering the brick and mortar from outside.

Retaining wall waterproofing must address the soil-facing side of the wall whenever possible. A membrane helps block water, while drainage board, aggregate, drainpipe, filter fabric, and properly directed outlets reduce the pressure behind the structure.

Concrete retaining wall waterproofing should also address cracks, construction joints, tie holes, penetrations, and wall-to-footing transitions.

For new walls, integral waterproofing can be added directly to concrete, mortar, grout, or compatible repair materials. Existing walls may require excavation, repairs, surface-applied products, and improved drainage.

No coating should be expected to stabilize a leaning wall or replace a working drainage system.

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

FAQs About Brick Foundation and Retaining Wall Waterproofing

Can a brick foundation be waterproofed?

Yes. Brick foundations can be waterproofed using mortar repairs, parging, exterior coatings or membranes, drainage, and properly sealed penetrations.

What is the best way to waterproof a brick foundation?

Exterior positive-side waterproofing is often the most complete method because it stops water before it enters the brick or mortar.

Should brick be sealed before waterproofing?

The wall should first be inspected, cleaned, and repaired. Whether a separate sealer is needed depends on the selected waterproofing system.

Can brick foundation walls be waterproofed from inside?

Yes, certain interior coatings and drainage systems may be used. However, water may still enter and remain inside the masonry.

Does waterproofing brick stop efflorescence?

It may reduce the moisture movement that causes efflorescence, but existing deposits and the source of water must also be addressed.

What is retaining wall waterproofing?

It is the use of coatings, membranes, repairs, and drainage systems to prevent water from passing through or damaging a wall that holds back soil.

Do retaining walls need waterproofing?

Many retaining walls benefit from waterproofing, especially when water staining, occupied space, sensitive finishes, or prolonged soil moisture are concerns.

Is drainage more important than retaining wall waterproofing?

Both are important. Waterproofing blocks water movement, while drainage reduces pressure behind the wall.

What are common retaining wall waterproofing products?

Common products include liquid membranes, sheet membranes, cementitious coatings, mineral-based products, rubberized coatings, drainage boards, and joint sealants.

What is the best retaining wall waterproofing product?

The best product depends on the wall material, water exposure, soil, movement, drainage, and project design.

How is a concrete retaining wall waterproofed?

The wall is cleaned and repaired before a compatible membrane or coating is installed. Drainage board, drainpipe, aggregate, and filter fabric may also be added.

Can retaining wall waterproofing be applied to the front of the wall?

It can be applied there in some situations, but positive-side waterproofing on the soil-facing side is generally more effective.

What is a drainage board?

Drainage board creates a pathway for water to move downward behind the wall and may also protect the waterproofing membrane.

Do retaining walls need weep holes?

Some designs use weep holes, but they may not be the only drainage component needed. The wall should have a complete water-management plan.

What causes water to leak through a retaining wall?

Common causes include saturated soil, failed drainage, cracks, porous masonry, open joints, missing membranes, and clogged weep holes.

Can waterproof paint stop water through a retaining wall?

It may help with light moisture, but it may not resist significant pressure from saturated soil behind the wall.

Should cracks be repaired before waterproofing?

Yes. Cracks, joints, voids, and penetrations should be evaluated and repaired before the main waterproofing system is installed.

Can a leaning retaining wall be fixed with waterproofing?

No. Leaning or bowing usually indicates a structural or soil-pressure problem. The wall should be evaluated and repaired appropriately.

Can waterproofing additives be used in a new retaining wall?

Yes. Compatible integral waterproofing products may be added to new concrete, mortar, or grout to improve water resistance throughout the material.

Does integral waterproofing replace drainage?

No. It improves the water resistance of the cementitious material but does not replace drainpipe, drainage aggregate, grading, or other water-management details.

Who can help me select brick or retaining wall waterproofing products?

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