House Wash Recipes: Quick-Reference Mix Ratios for Common Scenarios

Why recipes matter

Consistency beats guessing. These recipes are tested and proven. Use them every time for predictable results.

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Recipe #1: Standard vinyl siding (most common)

Best for: Clean vinyl, light mold, general dirt

Mixing ratio:

• 1 part SH (12.5% sodium hypochlorite)
• 2 parts water
• Add 1-2 oz surfactant per 5 gallons

Concentrate in tank:

• 5 gallons: 1.7 gallons SH + 3.3 gallons water + 1-2 oz surfactant
• 10 gallons: 3.3 gallons SH + 6.7 gallons water + 2-3 oz surfactant
• Total delivered: ~2-3% SH at nozzle (perfect for vinyl)

Application:

• Spray entire surface evenly
• Dwell time: 10-15 minutes (let it work)
• Rinse thoroughly with low pressure (40 degree nozzle)
• Work on cloudy days if possible (heat speeds evaporation)

Expected results:

• Dirt and light algae gone
• Finish looks new
• No damage to paint or caulk

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Recipe #2: Heavy mold/algae (green, black, or heavy growth)

Best for: Dark staining, heavy algae, mold-prone areas

Mixing ratio:

• 1 part SH (12.5%)
• 1 part water
• Add 1.5-2 oz surfactant per 5 gallons

Concentrate in tank:

• 5 gallons: 2.5 gallons SH + 2.5 gallons water + 1.5-2 oz surfactant
• 10 gallons: 5 gallons SH + 5 gallons water + 3-4 oz surfactant
• Total delivered: ~4-5% SH at nozzle

Application:

• Spray entire surface
• Dwell time: 15-20 minutes (let it work, don't rush)
• You'll see mold start to visibly lighten as it dies
• Rinse thoroughly
• In humid climates, let cure 24+ hours before rinsing (better kill)

Expected results:

• Dark staining mostly gone
• May require second application for extreme cases
• Longer kill time = longer lasting prevention

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Recipe #3: Stucco-safe (low-pressure alternative)

Best for: Stucco, ancient brick, soft masonry surfaces

Important: Stucco is porous and delicate. This recipe uses lower SH and gentler delivery.

Mixing ratio:

• 1 part SH (12.5%)
• 3 parts water
• Add 1-1.5 oz surfactant per 5 gallons

Concentrate in tank:

• 5 gallons: 1.25 gallons SH + 3.75 gallons water + 1-1.5 oz surfactant
• 10 gallons: 2.5 gallons SH + 7.5 gallons water + 2-3 oz surfactant
• Total delivered: ~1.5-2% SH at nozzle

Application:

• Use soft-wash nozzle (minimal pressure) or garden sprayer
• Spray gently — don't force the solution in
• Dwell time: 15-20 minutes
• Rinse gently with low pressure (white nozzle maximum)
• Never use red/yellow nozzles on stucco

Expected results:

• Surface cleaned without damage
• Results are slower than higher-concentration recipes (normal)
• No etching, erosion, or surface breakdown

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Recipe #4: Brick-safe (historic or sealed brick)

Best for: Brick homes, historic buildings, sealed surfaces

Key principle: Brick is porous but often sealed. Too strong a mix can damage pointing or seals.

Mixing ratio:

• 1 part SH (12.5%)
• 2.5 parts water
• Add 1-1.5 oz surfactant per 5 gallons

Concentrate in tank:

• 5 gallons: 1.6 gallons SH + 3.4 gallons water + 1-1.5 oz surfactant
• 10 gallons: 3.2 gallons SH + 6.8 gallons water + 2-3 oz surfactant
• Total delivered: ~2% SH at nozzle

Application:

• Spray evenly on entire surface
• Dwell time: 15-20 minutes
• Watch for discoloration (signs it's working)
• Rinse gently — don't blast pointing or mortar
• Use 40-degree nozzle at distance (2-3 feet away)

Expected results:

• Brick looks cleaner and color restored
• No damage to mortar pointing
• No sealer damage (with proper concentration)

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Recipe #5: Rinse-only (when not to use chemicals)

When to use this:

• Customer requests no chemicals
• Environmental restrictions
• Fragile plants nearby (customer concerned about runoff)
• Recently sealed surfaces (sealer instructions say no SH for 30 days)
• Light dust or pollen (pressure alone solves it)

Your formula:

• Water only (or water + minor surfactant for wetting)
• Higher pressure (2500-3000 PSI acceptable without chemicals)
• Lower angle (closer to surface, more aggressive)
• Multiple passes if needed

Application:

• Pre-rinse entire surface (loosen dirt)
• Spray with pressure, work methodically
• No dwell time (no chemistry working)
• Final rinse to settle dust

Expected results:

• Works for light to moderate dirt
• Heavy algae/mold won't come clean
• Honest with customer: "Pressure alone may not remove dark staining"

Price note: Rinse-only is simpler but often less impressive results. Price accordingly (lower) but be transparent about limitations.

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Mixing tips and tricks

Measuring accurately

For precise ratios:

• Use measuring cups or gallon jugs
• Mark your 5-10 gallon tank with tape (measure once, mark for future)
• Never eyeball it — consistency comes from precision

Quick estimates in field:

• 5-gallon bucket fills ~20 liters or 5.3 gallons (close enough)
• Use consistent scoops for chemical additions
• If unsure, go weaker — you can strengthen next batch, can't undo too strong

Surfactant selection

Good options:

• Elemonator or similar surfactant blends ($30-50/gallon) — industry standard
• Dawn dish soap (1-2 oz per 5 gallons) — cheap, works, but less effective
• Purpose-built house wash surfactants ($40-70/gallon) — premium option

Why it matters:

• Surfactant improves wetting and penetration
• Helps chemical reach dirt faster
• Reduces dwell time needed
• Better results than straight SH

Temperature effects

Cold weather (below 50°F):

• Chemical works slower — increase dwell time 5-10 minutes
• Evaporation slower (good: more time for chemistry)
• Rinse may be needed longer to fully clear

Hot weather (above 85°F):

• Chemical evaporates faster — decrease dwell time slightly
• Work faster to avoid having to re-spray
• Early morning or late afternoon best (cooler, slower evaporation)

Humidity effects

High humidity (>75%):

• Dwell time works better (water stays on surface longer)
• You can use slightly lower concentration and get same results
• Algae kill is faster (moisture helps)

Low humidity (under 40%):

• Evaporation very fast — spray and get to work immediately
• May need to increase concentration slightly
• Night work in arid climates helps (dew slows evaporation)

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Quick reference card (copy to your phone)

Vinyl/Standard: 1 SH : 2 water + surfactant → Spray, wait 15 min, rinse

Heavy Mold: 1 SH : 1 water + surfactant → Spray, wait 20 min, rinse

Stucco: 1 SH : 3 water + surfactant → Soft spray, wait 15 min, gentle rinse

Brick: 1 SH : 2.5 water + surfactant → Spray, wait 20 min, gentle rinse

Rinse Only: Water + 40° nozzle, multiple passes, no chemicals

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Testing protocol

Why testing saves you:

• Catches concentration errors before they affect whole surface
• Shows you results (helps manage customer expectations)
• Protects you from liability (you were careful)
• Gives you data for future jobs on similar surfaces

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Bottom line

Use these recipes. They work. Adjust only after testing. Document what works best for each surface type in your market. Over time, you’ll refine these based on your local climate, water quality, and customer expectations.

The goal: Consistent results, every time, without guessing.