Brick piers are a common and attractive structural element in residential construction, supporting porches, decks, entry canopies, and light-frame structures. However, when brick piers extend both above and below grade, they face a unique set of moisture challenges that can dramatically shorten their service life if not properly addressed. The interface between the buried portion of the pier and the surrounding soil is a zone of constant moisture exposure, where water, dissolved minerals, and freeze-thaw cycles work together to deteriorate both the brick and the mortar.
The rate of mortar deterioration in brick masonry is directly influenced by the length of time the masonry remains wet. Saturated brickwork is vulnerable to a cascade of problems: freeze-thaw damage in cold climates, efflorescence (the white, powdery deposit of soluble salts), spalling (surface flaking or chipping), and loss of bond between brick and mortar. Proper waterproofing of the below-grade portion of brick piers is therefore not merely a cosmetic concern but a structural necessity.
| Waterproofing Method | Material Cost (per sq ft) | Labor Cost (per sq ft) | Durability (years) | Suitable Soil Types | Relative Effectiveness |
|---|---|---|---|---|---|
| Parging + bituminous coating | $1.50 – $3.00 | $3.00 – $6.00 | 10-20 | All types | Good |
| Cementitious crystalline coating | $2.00 – $4.00 | $4.00 – $8.00 | 20+ | All types | Excellent |
| Sheet membrane (PE/PVC) | $3.00 – $6.00 | $5.00 – $10.00 | 25+ | Aggressive soils | Excellent |
| Liquid rubber membrane | $4.00 – $8.00 | $4.00 – $8.00 | 15-25 | Most types | Very good |
| Bentonite clay panels | $2.50 – $5.00 | $3.00 – $6.00 | 30+ | Swelling clays | Self-sealing, excellent |
Understanding Rising Damp
Rising damp is a phenomenon that occurs when moisture from the soil is drawn upward through the brick and mortar by capillary action. The pores in brick and mortar act like tiny wicks, pulling water upward from the saturated soil into the above-grade portion of the pier. In severe cases, rising damp can extend several feet above the grade line, keeping the lower portion of the pier continuously wet even during dry weather.
The height of rising damp depends on the pore structure of the materials, the rate of evaporation from the exposed surface, and the availability of moisture in the soil. A dense brick with small pores will have greater capillary rise potential than a more open-textured brick, but the actual height observed is usually limited by evaporation. In humid environments with limited air movement, rising damp can reach 3 to 5 feet above grade.
The consequences of rising damp are significant. The continuously wet masonry is more susceptible to freeze-thaw damage, which can cause brick faces to pop off (spalling) and mortar joints to deteriorate. Efflorescence is common on piers affected by rising damp, as water-soluble salts from the brick, mortar, or soil are carried to the surface where they crystallize as the water evaporates.
Below-Grade Waterproofing Methods
Below-grade waterproofing for brick piers involves creating a barrier that prevents soil moisture from entering the masonry. The two primary methods are cement parging combined with a bituminous foundation coating, and modern crystalline waterproofing systems applied to the masonry surface before backfilling.
The traditional and most common approach is to parge the below-grade portion of the pier with a 3/8-inch (10 mm) coat of mortar. The parging mixture consists of one part Portland cement to three parts clean, sharp sand by volume, mixed with sufficient water to achieve a workable consistency. The parging provides a dense, relatively impermeable layer that protects the brick and mortar from direct soil contact.
After the parging has cured for a minimum of seven days, a black foundation sealer (bituminous coating) is applied over the parging. The sealer is typically a solvent-based or water-based asphalt emulsion that forms a flexible, waterproof membrane. The coating should extend from the top of the footing to at least 2 inches above the finish grade line to ensure complete coverage of the below-grade zone.
Parging Application Technique
Proper application of parging is essential for its effectiveness. The surface of the brick pier should be clean and free of loose mortar, dirt, or efflorescence before parging begins. Any voids or open joints in the brickwork should be filled and struck flush before the parging coat is applied.
The parging mortar should be applied in one continuous coat, troweled firmly onto the pier surface to ensure good adhesion. The finished surface should be smooth and uniform, with no gaps or thin spots. The parging should extend from the top of the footing to the finished grade elevation, with special attention to the transition at the grade line where the exposed brick meets the parged surface.
The seven-day curing period is important. During this time, the parging should be kept moist (not saturated) to allow proper cement hydration and prevent shrinkage cracking. Moisture can be maintained by covering the parging with damp burlap or by misting it periodically. After curing, the surface should be dry before the foundation sealer is applied.
Foundation Sealer Application
Foundation sealers are typically applied with a brush, roller, or sprayer. Two coats are recommended for full protection, with the first coat allowed to dry according to the manufacturer’s instructions before the second is applied. The total dry film thickness should be at least 15 to 20 mils (0.015 to 0.020 inches) for effective waterproofing.
The sealer should be applied from the top of the footing to approximately 2 inches above the finish grade. Extending the sealer slightly above grade creates a visual “water line” and ensures that any splashing rain or snow melt that wets the pier at the grade line does not infiltrate below the waterproofing.
One important detail: if the pier is located in a region with aggressive soil chemistry (high sulfate or chloride content, acidic soil), a specialized foundation coating designed for such conditions should be specified. Standard bituminous coatings can degrade in contact with certain soil chemicals. The manufacturer should be consulted for recommendations specific to the project’s soil conditions.
Above-Grade Considerations: Leave Brick Exposed
Unlike the below-grade portion, the above-grade section of a brick pier should NOT be waterproofed or sealed. The exposed brick surface promotes rapid drying of any moisture that enters the pier from rainfall, splashing, or condensation. Sealing the above-grade portion of a brick pier can trap moisture inside, accelerating deterioration rather than preventing it.
The only exception to this rule is the application of a breathable, water-repellent treatment specifically designed for masonry. These treatments, known as silane/siloxane water repellents, penetrate the brick surface and line the pores with a hydrophobic (water-repellent) coating without blocking the passage of water vapor. This allows moisture within the pier to dry outward while preventing wind-driven rain from being absorbed.
If a water repellent is used, it should be applied only to the above-grade portion and should never bridge the transition to the below-grade waterproofing system. The water repellent and the waterproofing coating should have a gap at the grade line to allow a clear delineation between the two systems.
Drainage: The Supporting Cast
No waterproofing system can succeed without proper drainage. The soil around brick piers should be graded to divert surface water away from the pier base. For piers that are part of a larger structure with a footing drain system, the drain should extend around the pier footings as well.
At the base of each pier, a 6 to 12-inch gap filled with clean gravel or crushed stone provides a drainage path for any water that reaches the footing level. This gravel should be separated from the surrounding soil by filter fabric to prevent soil migration into the drainage media. A perforated drain pipe connected to the gravel zone can carry water away from the pier to a suitable outlet.
Above grade, the finished grade should slope away from the pier at a minimum of 5% (6 inches per 10 feet). If the pier supports a porch or deck, the floor above should be designed to shed rainwater away from the pier rather than directing it down the pier surface.
Maintenance and Inspection
Brick piers should be inspected annually, particularly after the winter season in cold climates. The inspection should check for: cracks in the below-grade parging (which may be visible above grade), separation between the parging and the brick, deterioration of the foundation coating where it is exposed at the grade line, signs of rising damp (dampness or efflorescence above grade), and spalling or pop-outs on the brick faces near the grade line.
If the parging or foundation coating is found to be damaged, the repair should be made promptly. For minor damage, a patch of parging mortar can be applied and coated with foundation sealer. For extensive damage, the pier may need to be excavated and the waterproofing system replaced entirely.
Efflorescence above grade is a sign that either the below-grade waterproofing has failed or the rising damp is exceeding the drying capacity of the exposed brick. If efflorescence is observed, the pier should be monitored for continuing moisture, and additional waterproofing measures may be needed.
Special Considerations for Different Climate Zones
In cold climates, frost heave is a significant concern for brick piers that extend below the frost line. The footings must be placed below the frost depth to prevent the pier from being lifted by frost action. The waterproofing system must be flexible enough to accommodate minor soil movements without cracking.
In warm, humid climates, the risk of rising damp is higher because evaporation rates are lower. Piers in these climates benefit from the maximum practical waterproofing protection below grade and the use of breathable water repellent treatments above grade to control moisture absorption from high humidity and frequent rainfall.
In arid climates, the primary concern is less about moisture and more about salt damage. Soils in dry regions often contain high concentrations of soluble salts. When these salts are carried into the brick by occasional rainfall or irrigation, they can recrystallize within the pore structure and cause spalling. A robust below-grade waterproofing system is essential to prevent salt-laden soil moisture from entering the pier at the base.
Waterproofing brick piers is a straightforward but critical construction task that requires attention to detail and an understanding of the mechanisms that cause masonry deterioration. The combination of cement parging and bituminous foundation coating, properly applied below grade, provides reliable protection against soil moisture and rising damp. Leaving the above-grade brick exposed allows it to dry naturally, completing a system that balances moisture exclusion with moisture management.
With proper waterproofing and drainage, brick piers can provide structural support for generations. Without it, the same piers may begin to show signs of deterioration within a few years, requiring expensive and disruptive repairs. The investment in proper below-grade waterproofing is a small fraction of the cost of pier replacement and is one of the most cost-effective measures a builder can take to ensure the long-term durability of masonry construction.
For more information on related construction topics, see our detailed guide on related building practices.