Efflorescence, the white powdery residue that appears on brick surfaces, happens when water moves through masonry, dissolves soluble salts inside, and carries them to the surface where they crystallize as the water evaporates. Preventing it comes down to one principle: keep water from entering and traveling through the brick. That means making smart choices before, during, and after construction.
Why Efflorescence Forms
Three ingredients must be present at the same time for efflorescence to occur: soluble salts within the masonry materials, moisture to dissolve and transport those salts, and a path for that moisture to reach the surface. Eliminate any one of these three and you won’t see white deposits on your brick. The salts can come from the brick itself, the mortar, the soil behind a retaining wall, or even the water used during mixing. Portland cement is a common culprit because it naturally contains sodium and potassium compounds that dissolve easily.
This is why efflorescence often shows up in the first year after construction. Fresh mortar is loaded with soluble salts, and any rain or groundwater that contacts the wall will start pulling those salts to the surface. The good news: once the salts are flushed out, efflorescence from that source stops. The bad news: if water keeps finding new paths into the wall, it can dissolve salts from deeper within the masonry for years.
Choose Low-Salt Materials
Prevention starts at the supply yard. Brick manufacturers test their products for efflorescence potential, and many produce lines specifically rated “not effloresced” under ASTM C67 testing. Ask your supplier for bricks with low soluble salt content. The same applies to mortar: use clean, washed sand and potable mixing water. Contaminated sand or water with high mineral content introduces extra salts into the wall before it’s even built.
Portland cement type also matters. Type II and Type V cements generally contain fewer alkalis than Type I. If efflorescence is a known concern in your climate or soil conditions, specifying lower-alkali cement for your mortar mix is a straightforward way to reduce the available salt load.
Protect Materials on the Job Site
Bricks and mortar bags sitting uncovered on a job site absorb rain and ground moisture, activating salts before construction even begins. Store brick pallets off the ground on raised platforms and cover them with waterproof tarps that still allow air circulation. OSHA limits loose brick stacks to 7 feet in height, with tapering required above 4 feet, but from an efflorescence standpoint the key issue is moisture exposure, not just stacking height. Keep bags of cement and dry mortar mix completely dry and sealed until use.
During construction, cover the top of unfinished walls at the end of each workday. Rain soaking into a partially built wall saturates fresh mortar joints and starts the salt migration cycle immediately.
Design Walls to Shed Water
The single most effective long-term defense against efflorescence is a wall system that moves water out before it can travel through the brick. This comes down to three elements: flashing, weep holes, and proper capping.
Through-wall flashing should be installed at every point where water might pool or enter the wall assembly. At the base of a cavity wall, flashing seals to the backup wall, projects downward to the foundation, and then angles outward to the face of the wall with a sloped drip edge. This catches any water that penetrates the outer brick layer and redirects it outside. Flashing is also critical above windows, doors, shelf angles, and anywhere the wall meets a roof line.
Weep holes or open head joints should be spaced no more than 32 inches apart along the base of the wall and above every flashing location. These openings must extend completely through the wall thickness so trapped water has a clear exit. Without functioning weep holes, water collects behind the brick, slowly wicking salts to the surface for months or years.
Wall caps and copings should overhang at least 4 inches beyond the face of the masonry and slope away from the wall on both sides. A flat or poorly sealed cap lets water run directly down the brick face, which is one of the most common causes of persistent efflorescence on garden walls, retaining walls, and parapets.
Add Water Repellents to the Mortar
Integral water repellent admixtures are liquid additives mixed directly into the mortar during batching. They work by reducing the capillary action inside mortar joints, making it harder for water to wick through the wall. These are typically liquid polymeric compounds added at the manufacturer’s recommended rate during mixing. The installer should follow the dosage precisely, since too little won’t provide adequate protection and too much can weaken the mortar bond.
Integral repellents are especially useful in single-wythe walls (walls without a drainage cavity), where there’s no air gap or flashing system to intercept moisture. They don’t eliminate the need for good flashing and drainage in cavity walls, but they add a meaningful extra layer of protection. Some brick manufacturers also produce units with water repellent built into the brick body itself, which can be paired with treated mortar for a fully repellent system.
Apply a Breathable Sealer After Construction
Surface sealers offer a final line of defense, but choosing the wrong type can make efflorescence worse. Film-forming sealers like epoxies and some acrylics sit on top of the brick surface. While they block water from outside, they can also trap moisture vapor inside the wall. That trapped moisture dissolves salts and deposits them just beneath the sealer, eventually causing the coating to peel or blister and creating an even worse appearance problem. Epoxies also tend to chalk and degrade under UV light, limiting them to interior use.
Penetrating silane-siloxane sealers work differently. Their molecules are small enough to soak into the pores of dense brick rather than forming a film on top. Once inside, they bond chemically to the pore walls and create a hydrophobic barrier that repels liquid water while remaining 100 percent breathable. Water vapor from inside the wall can still escape, which means salts don’t get trapped and pushed to the surface. The brick looks unchanged after application, with no glossy sheen or color darkening.
Apply a penetrating sealer only to clean, dry masonry. If efflorescence has already appeared, remove it first with a stiff brush and, if needed, a diluted acid wash (typically muriatic acid at a 1:10 ratio with water), then rinse thoroughly and let the wall dry completely before sealing. Sealing over existing salt deposits locks them in place and defeats the purpose.
Manage Drainage and Grading Around the Wall
Water doesn’t only enter a wall from the front. Groundwater wicking up through a foundation or pooling against a below-grade wall is a major and often overlooked source of efflorescence. Make sure the soil grade slopes away from the structure so rainwater drains away rather than collecting at the base. For retaining walls and foundation walls, a gravel backfill layer with a perforated drain pipe at the footing level keeps groundwater from saturating the masonry from behind.
Sprinkler systems that spray directly onto brick walls are another common offender. Each watering cycle pushes a small amount of moisture into the masonry, and over weeks and months this produces stubborn, recurring efflorescence. Redirecting sprinkler heads even a few inches away from the wall face can solve the problem entirely.
When Efflorescence Keeps Coming Back
If white deposits reappear after cleaning, the wall still has a moisture path that hasn’t been addressed. Persistent efflorescence on an older wall usually points to failed flashing, cracked mortar joints, missing or clogged weep holes, or a new water source like a plumbing leak or changed drainage pattern. Simply cleaning and resealing without fixing the moisture source guarantees the salts will return.
Repointing deteriorated mortar joints with fresh mortar containing an integral water repellent can help. For walls where flashing was never installed or has failed, a mason can cut in new flashing at critical locations, though this is more invasive and costly. In many cases, a combination of repointing, applying a penetrating sealer, and correcting exterior drainage is enough to stop the cycle for good.