How to Clean and Reseal Exterior Brick (4 Steps for Lasting Protection)

TL;DR: Exterior brick should be cleaned and resealed every 5–7 years to stop water infiltration that leads to freeze-thaw cracking, efflorescence, and mortar deterioration. Power wash (800–1200 PSI) with a 15° nozzle, let dry 48–72 hours, then apply a breathable silane/siloxane sealer in two coats. Skip sealing if mortar is crumbling — repoint those joints first.

_Last reviewed: July 2026 · 6 min read_

Brick looks indestructible until water gets in. Freeze-thaw cycles crack the face, white salt blooms (efflorescence) appear after rain, and mortar joints start to powder. Cleaning and sealing every 5–7 years stops these problems before they demand expensive masonry repair. This guide covers when to clean, how to wash safely, what sealers work, and when to call a pro.

Okoniq Property Hub logs exterior maintenance dates and attaches before/after photos so you know exactly when the next reseal is due.

When should you clean and reseal exterior brick?

Clean and reseal if:

• The brick has been exposed for 5+ years without treatment.
• You see white efflorescence stains (salt deposits leached from the mortar).
• Water no longer beads on the surface — it soaks in.
• You plan to paint or coat the brick (cleaning is mandatory first).

Do not seal if mortar joints are crumbling or missing. Water trapped behind a sealer accelerates decay. Repoint the mortar first, then seal 6–8 weeks later when the new mortar has cured.

Check the brick after heavy rain. If dark wet patches linger for hours, the old sealer has failed or was never applied. Unprotected brick in northern climates will spall (flake) within 10–15 years as freeze-thaw cycles expand trapped water.

Spring and fall are ideal — temperatures between 50–85°F, low humidity, and no rain forecast for 48 hours before and after sealing. Avoid sealing in full sun; the sealer dries too fast and won't penetrate.

How do you clean exterior brick before sealing?

Start with a garden hose rinse to remove loose dirt. For heavy staining, rent or buy a pressure washer rated 800–1200 PSI with a 15° nozzle. Higher pressure or a 0° nozzle will blast mortar out of joints.

Hold the wand 12–18 inches from the surface, angle downward, and overlap passes. Work top to bottom so dirty runoff doesn't streak cleaned areas. For organic stains (mold, algae), mix 1 part bleach to 3 parts water in a pump sprayer, let sit 10 minutes, then pressure wash. For efflorescence, use a masonry cleaner (diluted muriatic acid) following the label — always wet the brick first, apply cleaner, scrub with a stiff brush, then rinse thoroughly.

Let the brick dry 48–72 hours. Use a moisture meter if available — readings should be below 15% before sealing. Wet brick traps moisture behind the sealer and causes blistering or peeling within months.

Never sandblast historic or soft brick. It removes the hard outer surface and accelerates weathering. If you're unsure of brick age or hardness, test a small section with medium pressure before committing.

What type of sealer should you use on exterior brick?

Use a penetrating breathable sealer, not a film-forming topcoat. Silane/siloxane blends are the standard — they soak into the brick and repel water while allowing trapped moisture to escape. Film sealers (acrylics, urethanes) trap moisture and peel within 2–3 years.

Look for products labeled "breathable" or "vapor-permeable" with a water vapor transmission rate above 50 perms. Popular brands include PROSOCO, SiloxaneWR, and DRYLOK Siloxane. A 5-gallon pail covers 250–500 square feet depending on brick porosity — older brick absorbs more.

Apply two coats with a low-pressure pump sprayer (not a paint roller — uneven coverage leaves streaks). The first coat soaks in within 10–15 minutes. Apply the second coat immediately after the first appears dry to the touch. Total coverage should be 100–200 square feet per gallon for both coats combined.

Work in 3–4 foot sections to maintain a wet edge. Overspray on glass, siding, or painted trim wipes off easily within 10 minutes but cures permanent if left overnight. Mask adjacent surfaces or keep a rag and mineral spirits handy.

Reapplication every 5–7 years maintains protection. Silane/siloxane sealers wear gradually — they don't peel or blister, they just lose effectiveness. Log the application date and check water beading annually.

How do you maintain sealed brick between applications?

Rinse the brick once a year with a garden hose to remove dirt and prevent buildup that traps moisture. Check mortar joints for cracks or gaps — repoint any deteriorated sections before water enters the wall cavity.

Inspect downspouts and gutters. Overflowing water saturates brick faster than rain alone. If you see persistent wet patches below a gutter, extend the downspout or add a splash block to divert runoff.

Trim vegetation at least 12 inches away from brick. Ivy and climbing plants hold moisture against the surface and accelerate efflorescence. Their roots also widen mortar joints.

Test the sealer annually by splashing a small area with water. If it beads for 5+ seconds, the sealer is intact. If water soaks in immediately, plan a reseal within the next 6 months.

If you notice new cracks, white powder between bricks, or flaking (spalling), call a mason for an inspection. These are signs of deeper structural issues — water infiltration behind the brick, inadequate drainage, or failed flashing around windows and doors.

When should you hire a professional instead?

Call a mason if:

• Mortar joints have gaps wider than 1/4 inch or crumble when scraped.
• Brick faces are flaking or chipping (spalling) — a sign of freeze-thaw damage.
• Efflorescence reappears within 6 months of cleaning (indicates a moisture source behind the wall).
• The building is 3+ stories and requires scaffolding or lifts.
• The brick is historic (pre-1900) or soft — improper cleaning or sealing destroys the surface.

A professional tuckpointing and sealing job on a 1,500 square foot facade costs $2,000–$4,000 depending on scaffolding needs and mortar condition. DIY sealing alone (pressure washer rental + sealer + sprayer) runs $150–$300 for the same area.

If the brick has never been sealed and is 20+ years old, a mason should inspect first. Hidden damage behind the surface may require repair before sealing makes sense.

FAQ

How long does brick sealer last?

Silane/siloxane sealers last 5–7 years in most climates. Northern freeze-thaw zones may see 4–5 years before reapplication is needed. Film-forming sealers (acrylics) fail in 2–3 years and are not recommended for exterior brick.

Can you seal brick in cold weather?

No. Apply sealer when air and surface temperatures are 50–85°F with no rain or frost forecast for 48 hours. Cold temperatures prevent penetration, and frost can blister the sealer before it cures.

What is efflorescence and how do you prevent it?

Efflorescence is white salt residue leached from mortar when water migrates through the brick. Prevent it by sealing the brick, fixing gutter leaks, and ensuring proper drainage away from the foundation. Clean existing efflorescence with a masonry cleaner (diluted muriatic acid) before sealing — it won't disappear under sealer.

Should you seal painted brick?

Painted brick rarely needs a separate sealer — the paint acts as a barrier. If repainting, clean thoroughly and use a breathable masonry paint designed for exterior brick. Never seal over peeling paint; scrape it off, prime, and repaint.

How do you remove old sealer from brick?

Most penetrating sealers wear away naturally and don't require removal. If a film-forming sealer is peeling, use a chemical stripper formulated for masonry (follow manufacturer directions), then pressure wash. Let the brick dry 72+ hours before applying a breathable sealer.

This is educational information, not structural or engineering advice. Consult a licensed mason if you see cracking, spalling, or persistent moisture issues behind the brick.