Brick looks rugged, but the surface is more delicate than people realize. Acidic cleaners can dissolve mortar joints, pressure washing at the wrong PSI strips the fired skin, and the wrong brush leaves metal flecks that rust and stain. Cleaning brick properly takes the right combination of cleaner, dwell time, and mechanical action — and the methods change dramatically depending on whether you are working on an exterior wall, a fireplace, or a patio. Get it right and your brick lasts another 50 years. Get it wrong and you accelerate decay you cannot reverse.
- Understanding Brick Before You Clean It
- Methods for Exterior Brick Walls
- Light Dirt and Mildew
- Heavy Mildew and Algae
- Efflorescence (White Crystalline Deposits)
- Paint, Graffiti, and Stains
- Cleaning Brick Fireplaces
- Brick Patios and Walkways
- Tools You Need
- What to Avoid
- Sealing After Cleaning
- When to Call a Pro
- Realistic Cost and Time
- FAQ
Understanding Brick Before You Clean It
Most residential brick is fired clay with a hard outer “fire skin” that is largely waterproof. The inner core is more porous. If you abrade the fire skin away with aggressive cleaning, you expose porous interior brick that absorbs water, freezes, and spalls (flakes off) in winter. This is why pressure washing brick at high PSI is one of the most damaging things homeowners do.
Mortar joints are even more vulnerable. Modern mortar is portland cement based and resists acid better than older lime mortar, but acidic cleaners still etch and weaken joints over time.
Methods for Exterior Brick Walls
Light Dirt and Mildew
Mix one cup of trisodium phosphate (TSP) substitute and one quart of bleach into a gallon of water. Apply with a soft-bristle brush, let dwell 5 minutes, scrub gently, and rinse with a garden hose at normal pressure. This handles 80% of exterior brick cleaning jobs.
Heavy Mildew and Algae
Use a dedicated outdoor brick cleaner like Wet & Forget (about $30 per gallon). Spray on, walk away, let rain do the work over the following weeks. No scrubbing, no rinsing. This works because the surfactant penetrates and continues breaking down organics over time.
Efflorescence (White Crystalline Deposits)
Efflorescence is salt that wicks to the surface as moisture evaporates through brick. Brush off dry deposits with a stiff nylon brush. If they persist, use a 5% white vinegar solution sparingly, then rinse thoroughly. Fix the underlying moisture source or efflorescence will return.
Paint, Graffiti, and Stains
Use a dedicated brick paint stripper like Peel Away 7 ($60 per gallon). Apply, cover with the supplied paper, wait 24 to 48 hours, then peel and scrape. For graffiti, World’s Best Graffiti Remover handles most paints without damaging brick.
Cleaning Brick Fireplaces
Soot and creosote require different approaches than exterior dirt. Start with a stiff dry brush to remove loose soot — never wet brick before this step or you will smear soot deep into the pores.
For light soot, mix dish soap with warm water and scrub with a soft brush. For heavy soot, mix one part TSP with six parts warm water plus one part bleach. Apply with a sponge from bottom to top (counterintuitive, but prevents streak marks), let dwell 5 minutes, scrub, and wipe with clean water.
For stubborn smoke staining on the firebox face, use a paste of cream of tartar and water. Apply, let dry, and brush off. This trick has been used by chimney sweeps for over a century and still works.
Brick Patios and Walkways
Sweep first to remove debris. Pull weeds from joints by hand or with a flame weeder. Apply Wet & Forget for organic growth or use a 30:1 dilution of household bleach for faster results.
Power washing brick patios is acceptable at 1,500 PSI maximum with a 25 or 40 degree fan tip held at least 12 inches from the surface. Anything stronger blasts mortar out of the joints and erodes the brick face. Plan to re-sand polymeric joint sand afterward.
Tools You Need
- Soft to medium nylon bristle brushes (avoid metal — metal flecks rust and stain)
- Garden pump sprayer for cleaner application
- 5-gallon buckets, rubber gloves, safety glasses
- Drop cloths for protecting plants and paint
- Garden hose with adjustable spray nozzle
- Optional: pressure washer set to 1,500 PSI maximum
What to Avoid
- Muriatic acid (full strength): The classic mistake. Burns skin, etches brick, dissolves mortar. If you must use it, dilute 1:10 minimum and rinse aggressively.
- Wire brushes: Embed metal flecks that rust and create permanent orange stains.
- High-pressure washing above 2,000 PSI: Strips the fire skin and forces water deep into mortar joints.
- Cleaning in freezing weather: Water in joints freezes and cracks brick.
- Cleaning in direct hot sun: Cleaners evaporate before they work and can leave streaks.
Sealing After Cleaning
After exterior brick is cleaned and fully dry (allow 48 hours), consider applying a breathable masonry sealer like Prosoco SureKlean Weather Seal Siloxane PD ($80 per gallon, covers about 200 sq ft). This prevents future mildew and reduces water absorption. Avoid film-forming sealers that trap moisture inside the brick.
For fireplaces, do not seal. Sealers can off-gas dangerous fumes when heated and reduce the brick’s ability to absorb and release heat properly.
When to Call a Pro
For brick walls over 2 stories, severe efflorescence indicating water infiltration, historic mortar (lime-based, found in pre-1930 buildings), or whole-house cleaning jobs, hire a masonry restoration specialist. They charge $1,500 to $4,500 for a typical single-family exterior, and they have the equipment and chemistry knowledge to clean without damage.
Repointing — replacing failed mortar — is also pro work. If your mortar joints crumble during cleaning, the joints need professional attention before any sealing happens.
Realistic Cost and Time
- 200 sq ft brick wall DIY: $30 to $80 in cleaner, 4 to 6 hours
- Same job hired out: $400 to $900
- Brick fireplace face DIY: $20 in supplies, 2 to 3 hours
- 500 sq ft brick patio: $60 in cleaner plus $20 polymeric sand, full weekend
FAQ
Is vinegar safe for cleaning brick?
Diluted vinegar (5% or weaker) is safe for spot use but should not be used on large areas. The acid weakens mortar joints over time.
Can I pressure wash brick?
Yes, but at 1,500 PSI maximum with a wide fan tip held at least 12 inches away. Higher pressure damages the brick face and joints.
How often should I clean exterior brick?
Every 3 to 5 years for general maintenance. Sooner if you see green algae growth or heavy efflorescence.
Will the cleaning process remove old paint?
Standard cleaners will not. You need a brick-rated paint stripper like Peel Away 7 to remove paint without damaging the brick surface.
What is the safest cleaner for indoor brick?
A mix of dish soap and warm water handles most indoor brick. For tougher jobs, dilute TSP works without strong fumes when ventilated.
