Preventing Efflorescence on New Brick: Water Sources, Curing, and Best Practices

Efflorescence is a white or pale bloom that appears on masonry surfaces. It can be mistaken for a structural problem, but it is primarily a surface phenomenon. Understanding the difference helps guide the right mitigation steps.

The basic mechanism involves water moving salts from within the masonry to the surface as it evaporates. When water evaporates, dissolved salts are left behind, forming the visible coating or crystals on brick or mortar faces.

Chemical and Physical Causes

Efflorescence is caused by soluble salts moving through your new brickwork. These salts come from a few places:

• Masonry cement: It contains salt that can leach out.
• Brick and mortar: Some bricks and mortars have naturally occurring salts.
• Groundwater: If your site has high groundwater levels, it might contain salts.

The process goes like this:

• Water moves through tiny capillaries in the brickwork, picking up salts along the way.
• This water then evaporates at the surface, leaving the salts behind.

Visual Signs, Timing, and Severity Assessment

Efflorescence appears as a white, powdery deposit on the surface of your brickwork. Here’s how to tell if it’s fresh or old:

• Fresh efflorescence: It’ll be white and fluffy, like snow.
• Old efflorescence: It’ll be grayish or yellowish, and might be harder to the touch.

It usually appears on:

• The top courses of walls.
• Vertical joints.
• Anywhere water tends to pond or drip.

To assess severity, look for signs of active moisture movement. If the efflorescence is growing or changing color, it’s still active.

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External sources include rain, runoff, and groundwater that can infiltrate the wall system. Internal sources are moisture produced inside the building structure, such as condensation or plumbing leaks. Construction-related water comes from curing moisture or improper drainage around the wall.

The core strategy is to minimize water entry and accumulation. Identify and address likely water paths and monitor for any ongoing leaks or seepage that could feed salt movement.

External water paths (rain, splash, roof/runoff)

Efflorescence loves to sneak in through gaps and cracks on the outside of your brickwork. Here’s how:

Poor flashing around windows, doors, and chimneys can let rainwater trickle down behind the bricks. Missing or inadequate overhangs above doors and windows don’t protect the walls from direct rain impact. Surface splash from rain hitting the ground below can also send water up into your brickwork.

To keep external water out, ensure proper flashing installation, maintain overhangs, and consider using a liquid membrane on walls that are prone to splash.

Ground and rising moisture, drainage issues

Water from below can cause efflorescence too. Here’s how it happens:

Sub-surface water finds its way up through capillary action, especially if your bricks are porous or there’s no barrier to stop it. Inadequate site drainage means water lingers around the base of your walls, encouraging efflorescence.

To combat this, ensure a proper damp-proof course is installed at the base of your walls. Sloping the ground away from the walls helps too, improving site drainage and reducing moisture buildup.

Construction and material moisture (wet mortar, stored units)

Material choices during construction can also contribute to efflorescence. Here’s what to watch out for:

• Wet mortar: Using too much water in your mortar mix leaves excess moisture that can’t escape, leading to efflorescence.
• Stored units: Storing bricks outside before use exposes them to rain and dew. This extra moisture gets trapped when they’re laid.
• Mixing water: Using impure or salty water in your mortar mix introduces salts that will later appear as efflorescence.
• On-site water handling: Poorly controlled water sources on site can lead to accidental contamination of materials.
• Wrong material choice: Using bricks with high salt content or poor absorption rates can result in cracking, staining, and weak bond due to trapped moisture.

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Brick quality and the mineral content of the units influence how much salt is available to migrate. Mortar constituents and the moisture handling during mixing also affect salt transport. Use clean water and keep mixing conditions stable to avoid introducing contaminants.

Store materials properly to reduce exposure to rain or damp conditions before installation. Check product labels and manufacturer instructions for guidance on storage and handling related to salts and pozzolanic additives.

Brick selection and on-site storage practices

Choosing the right bricks is crucial to prevent efflorescence. Go for low-salt, well-fired bricks when possible.

Why? High salt content in bricks can lead to efflorescence. Well-fired bricks have less salt and are better quality.

Store your bricks properly on-site too. Keep them off the ground and under cover to limit moisture pickup.

Why bother? Moisture can dissolve salts, leading to efflorescence. Keeping bricks dry reduces this risk.

Mortar selection, water quality, and admixtures

Mortar composition and mixing water quality matter. Low-salt mortar and clean water help prevent efflorescence.

What’s low-salt mortar? It has less salt content than regular mortar. Ask your supplier for options.

Use clean mixing water too. Rainwater or well-water can have high salt content, so avoid them if possible.

Admixtures can help. Check manufacturer guidance to see which ones reduce soluble salts in your specific case.

Testing for soluble salts and reporting needs

Get pre-installation testing done by an accredited lab. Test for soluble salts and moisture profiling.

Why test? It helps you understand the salt content in your materials and if there are any moisture issues.

Request clear test limits from project specifications. This ensures everyone’s on the same page about what’s acceptable and what’s not.

When to test? Do it before installation. That way, you can address any issues before they become problems.

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Controlled curing helps keep water within the wall system long enough for proper hydration without promoting excessive salt movement. Curing methods should align with the local conditions and the masonry assembly design. Avoid practices that trap overly moist surfaces during hot, windy, or drying conditions.

Consider how curing choices interact with ambient weather to affect final appearance. When in doubt, verify recommended curing procedures with the product data sheet or manufacturer instructions.

Principles of curing relevant to salt movement

Curing is crucial for minimizing efflorescence. It’s about controlling how moisture leaves the brick.

Slow, even curing lets water escape gradually. This gives salts time to move out with the water, rather than being left behind as the brick dries too fast.

Moisture retention helps keep the brick hydrated uniformly. This ensures a consistent pore structure throughout the brick. Inconsistent pores can trap salts and push them to the surface.

Uniform hydration also prevents stress within the brick. Stress can cause cracks, which become pathways for salt migration.

Practical curing methods and selection criteria

There are several ways to cure your bricks. Each has its pros and cons:

Wet curing involves keeping the brick surface wet for a few days after laying. This is simple but can be messy and time-consuming.

Damp covers, like burlap or plastic sheets, retain moisture but allow air circulation. They’re easy to use but may need frequent wetting.

Membrane curing uses special compounds that form a protective layer on the brick surface. These are convenient but can be more expensive.

Choose based on your job’s needs and manufacturer instructions. Always consider your site conditions – temperature, humidity, wind, etc.

When to use curing compounds or membranes

Curing compounds or membranes can be a good choice when you need more control over the curing process:

They’re great for large projects where consistent, even curing is crucial. They can also help in harsh weather conditions like high winds or extreme temperatures.

However, they may not be necessary for small jobs or mild climates. Wet curing or damp covers might suffice.

Always check if the compound is compatible with your bricks and any coatings you plan to use. Some compounds can react negatively with certain materials.

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Passive details like flashing, weeps, and proper drainage planes direct water away from the masonry. Overhangs and coping work with gravity and shading to reduce water infiltration. The goal is to keep the wall dry during normal service conditions.

Think through the path water would take and install details that interrupt that path before it reaches the brick or mortar. Check design notes and local building guidance for any specific detailing requirements for your project.

Flashing, Weep Holes, and Cavity Drainage

Flashing is your first line of defense against water intrusion. It’s a thin sheet of metal or plastic that diverts water away from vulnerable areas like windows, doors, and corners.

Install it at these locations, lapping up and under masonry to create a watertight barrier. Weep holes, tiny openings in the mortar joints near the bottom of walls, let any trapped water escape. Space them evenly, about every 30 inches or so.

Cavity drainage systems are another tool. They’re plastic channels installed behind masonry that collect and direct water to weep holes. Use them in areas with high moisture risk.

Joint Profiles, Pointing and Coping Details

The shape of your mortar joints can make a big difference. Concave joints shed water better than flat or convex ones. They slope slightly inward, encouraging water to run off.

Pointing is the process of filling and finishing mortar joints. A st struck joint, where the mortar is pressed into the joint and then scraped flush with the face of the brick, is best for preventing efflorescence. It leaves no pockets for water to sit in.

Coping details at the top of walls are crucial too. A proper coping overhang keeps rain from splashing back onto the wall. Use a drip edge or a sloped coping piece to direct water away.

Wall Assemblies and Substrate Compatibility

Your wall needs to breathe, so use compatible substrates. Brick on wood studs is a no-no; they expand and contract at different rates. Use concrete or steel backups instead.

Air/moisture barriers like house wrap or fluid-applied membranes stop water from getting in but let moisture out. Install them behind your masonry, but don’t seal the bottom. You need that path for water to escape.

Ties hold the wall together and help it drain. Use expansion ties that allow movement while keeping the wall secure. And make sure they’re properly spaced – usually every 16-24 inches vertically, and every 30-36 inches horizontally.

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