House Wash Mix Recipes: Professional Ratios for Every Surface

Key Takeaways

• Standard house wash = 1% SH (sodium hypochlorite) - Strong enough to clean, safe for most surfaces
• Surfactant is non-negotiable - Without it, chemicals run off before working
• Always add chemicals to water - Never water to chemicals (safety rule)
• Mix fresh daily - SH loses potency over time
• Test surface first - Some materials can’t handle even 1% SH

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Understanding House Wash Chemistry

The Three Components

Sodium Hypochlorite (SH) is your workhorse—12.5% strength from a pool supplier, not grocery store bleach. It kills the organic growth that makes houses look bad: algae, mold, mildew. The percentage matters because you’re cutting it down to strength for different jobs.

Surfactant is the soap that actually makes the chemicals stick. Without it, your mix runs off before it does anything. It also breaks down dirt and creates that foam that clings to vertical surfaces. Pros have their favorites—Elemonator, Gain, Simple Cherry—but most work fine once you dial in the ratio.

Water is your carrier. It dilutes the SH to safe levels and gets everything where it needs to be.

The Sweet Spot: 1% SH

Most house washing jobs call for 1% sodium hypochlorite. It’s strong enough to kill growth without stripping paint or scorching landscaping. You’ll find this concentration in just about every pro’s playbook.

Go to 2-3% when you’re facing real neglect—heavy black streaks, years of buildup, or pre-painting prep where you need it spotless. Roof cleaning needs the extra punch too.

Drop to 0.5% on anything delicate: surfaces you’re not sure about, homes you cleaned recently, expensive materials that can’t take the hit. Test first every time.

North-facing walls collect shade-loving algae that standard 1% struggles with, so bump it to 1.5% and add extra surfactant to help it cling longer. Painted wood siding gets the lightest touch—0.5% maximum, and honestly soft washing is better for that anyway.

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Essential Equipment for Mixing

You need basic stuff. You don’t need to buy much.

A 5-gallon bucket is your mixer. Measuring cups for SH and surfactant—keep them completely separate or they’ll react weird. Permanent marker for labeling. A funnel saves spills. That’s the core.

Safety Gear (Non-Negotiable)

PPE requirements aren’t optional—they exist because of real hazards. Learn the complete chemical safety requirements.

SH exposure in the eyes causes severe chemical burns requiring immediate medical attention. Use goggles with full seal around the eyes, not safety glasses. Chemical-resistant gloves (nitrile or rubber) protect against caustic burns. Respirator at minimum N95, or a half-face respirator if mixing daily. Wear a rain suit or apron as a barrier against chemical splash and skin exposure.

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Standard House Wash Mix (1% SH)

For 5 Gallons:

• Water: 4 gallons + 64 ounces (approx. 4.6 gallons total)
• 12.5% SH: 12 ounces (1.5 cups)
• Surfactant: 2-4 ounces

The Order Matters:

1. Pour water first—4+ gallons into the bucket
2. Add surfactant, stir it in
3. Add SH slowly while stirring gently
4. Label it: “House Wash 1% SH” and the date

This is critical for safety: Always add chemicals to water, never water to concentrated SH. Water striking concentrated bleach creates a violent chemical reaction with dangerous splash-back. This is a fundamental rule across all pressure washing operations. Chemicals into water is safe. Water into chemicals is dangerous.

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Surface-Specific Mix Recipes

Vinyl Siding

Use the standard 1% recipe. Apply with a black soap nozzle (65° fan), work bottom to top, let it sit 5-10 minutes without drying, then rinse top to bottom with a white or green tip.

Don’t go over 1.5% SH on vinyl—you’ll start stripping paint or worse. Never use red or yellow tips, keep 10-12 inches away, and don’t spray upward at an angle. Water behind the siding causes problems.

Stucco and EIFS

Go lighter here—0.75-1% SH. For 5 gallons: 4.5+ gallons water, 9 ounces SH, 3-4 ounces surfactant.

Use a white nozzle (40° fan), apply gently with even passes—don’t focus on one spot. Let it dwell 5-7 minutes; stucco is porous and soaks it up. Rinse multiple times because stucco holds chemicals deep.

Test in an inconspicuous spot first; stucco varies wildly. Never exceed 1,500 PSI. Stay 12+ inches away. If the color starts coming off, stop immediately.

Brick and Masonry

Go 1-1.5% depending on what you’re dealing with. For 5 gallons at 1.5%: 4.5 gallons water, 18 ounces SH, 4-6 ounces surfactant.

Apply with a green nozzle (25°), let it sit 10-15 minutes—brick is porous and needs the time. Scrub stubborn spots with a stiff brush. Rinse thoroughly with multiple passes.

Some brick colors fade, so test first. Mortar joints are softer than brick, so watch for erosion. Old brick gets the lighter 1% treatment.

Painted Wood Siding

This is tricky. Use 0.5-0.75% max. For 5 gallons at 0.5%: 4.8 gallons water, 6 ounces SH, 4-6 ounces surfactant.

Apply extremely gently. White nozzle (40° fan) only. Let it dwell 3-5 minutes but don’t let it dry. Rinse right away if the paint starts lifting.

Honestly, soft wash is better for painted wood. Test multiple spots because paint varies. If it’s fragile or expensive, hand wash it or call a pro. Paint repair costs way more than having someone else clean it.

Fiber Cement Siding (Hardie Board)

Standard 1% recipe works fine. Use white or green nozzle, dwell 5-10 minutes, rinse top to bottom.

Hardie board handles pressure washing well and is tougher than vinyl, but still stay under 2,000 PSI.

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Heavy-Duty Mixes

Neglected House Mix (2% SH)

When you’re dealing with a house that hasn’t been touched in years, or heavy black algae buildup:

For 5 Gallons: 4.2 gallons water, 24 ounces SH, 6-8 ounces surfactant

Rinse very thoroughly afterward—this is stronger stuff. Protect plants carefully. Always test the surface first. The two-pass method works well: apply, rinse, apply fresh mix again, rinse thoroughly.

Pre-Painting Prep (1.5-2% SH)

Painters want spotless surfaces. Kill all the organic growth, remove chalking, leave it perfect.

For 5 Gallons (1.5%): 4.4 gallons water, 18 ounces SH, 6-8 ounces surfactant

Apply it, let it dwell 15 minutes, scrub with a soft brush if needed, rinse thoroughly multiple times. Let it dry 48 hours before the painter shows up.

North-Facing Walls (1.5% SH)

Shade-facing walls stay wet and grow heavy algae and mold that regular 1% struggles to handle.

For 5 Gallons: 4.4 gallons water, 18 ounces SH, 8 ounces surfactant (extra)

The extra surfactant helps it penetrate the heavy growth and stay wet longer in the shade. More foam means it clings better to shady surfaces.

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Surfactant Options

Elemonator is professional-grade—thick foam, excellent clinging, neutralizes bleach smell. At 2-3 ounces per 5 gallons, it’s $60-80 per batch. Worth it if you’re doing this regularly.

Gain Original is cheap and available everywhere—$15-20 per batch at 4-6 ounces per 5 gallons. Decent foam, doesn’t neutralize smell, but gets the job done.

Simple Cherry has red dye so you can see where you’ve sprayed—also 4-6 ounces per batch, same price as Gain. The dye can stain if you’re not careful.

For surfactant amounts, the standard is 2-4 ounces per 5 gallons. Go heavier (6-8 ounces) on vertical surfaces, heavy growth, hot days, or second-story work where you need it to cling and stay wet. Less (2 ounces) on flat surfaces or light cleaning where it naturally stays on longer.

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Mix Calculation Shortcut Guide

Quick Reference: 5-Gallon Batches

Target SH %	12.5% SH Needed	Water Needed	Surfactant
0.5%	6 oz (¾ cup)	4.8 gal	4-6 oz
0.75%	9 oz (1 cup)	4.6 gal	4-6 oz
1%	12 oz (1.5 cups)	4.5 gal	2-4 oz
1.5%	18 oz (2.25 cups)	4.4 gal	6-8 oz
2%	24 oz (3 cups)	4.2 gal	6-8 oz
3%	36 oz (4.5 cups)	3.9 gal	8-10 oz

Quick Reference: 1-Gallon Batches

Target SH %	12.5% SH Needed	Water Needed
1%	2.4 oz	~1 gallon
1.5%	3.6 oz	~1 gallon
2%	4.8 oz	~1 gallon

Note: For small batches, use our Chemical Dilution Calculator for precise measurements.

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Mixing Best Practices

The Dos:

• Add chemicals to water, every time, no exceptions
• Mix outside where you’ve got air flow; SH fumes can knock you out indoors
• Wear full PPE even for quick mixes—that’s when accidents happen
• Label every container clearly with what it is and the date
• Mix fresh daily; SH loses strength over time
• Use containers just for chemicals, never reuse them for anything else
• Rinse the bucket when you’re done

The Don’ts:

• Never mix SH with acids (creates chlorine gas—deadly)
• Never mix SH with ammonia (also toxic gas)
• Never use hot water; SH breaks down faster and fumes get worse
• Never store mixed chemicals longer than 24 hours
• Never reuse measuring cups; cross-contamination causes unpredictable reactions
• Never mix in open containers where kids, pets, or wind can get to it

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Storage and Disposal

Mixed chemicals last 24 hours max. Mark the date on the bucket. Keep it out of direct sun and in a cool place—heat and UV kill the potency fast.

Concentrated SH stays in the original pool-supply container, in a cool dark place, kept upright. It lasts 6-12 months, so check the expiration. Store acids separately.

To dispose of unused mixed chemical, dilute it heavily with water (10:1 ratio) and pour it down a sanitary sewer, never a storm drain. Check local rules—some areas have restrictions. Empty containers get triple-rinsed, air-dried, and recycled if possible. Mark them “empty” so no one gets confused.

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Troubleshooting

Mix not cleaning? Check concentration first—jump from 1% to 1.5%. Add more surfactant (helps penetration). Extend dwell time to 15 minutes. Make sure you’re applying thick enough to see foam coverage.

Plants browning? You’re not rinsing plants enough before and during the job. Rinse them again after. Cover delicate plants with tarps. Water landscaping repeatedly while you work. Diluted vinegar rinse helps with residual chemical burns.

House still dirty after rinsing? The SH is probably too weak or degraded. Try the two-pass method: apply, dwell 10 minutes, rinse, apply fresh mix, dwell 15 minutes, rinse thoroughly. Scrub stubborn spots with a soft brush. Make sure your SH isn’t old.

Chemicals drying too fast? Sunlight, heat, and wind kill your dwell time. Work in smaller sections. Mist with plain water if it’s drying. Work early morning or late afternoon, away from peak sun. More surfactant helps retain moisture. Pick an overcast day if you can.

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Cost Comparison

Pre-mixed house wash runs $15-20 per gallon, so $75-100 per 5 gallons. You’re paying for convenience and someone else’s markup.

DIY at 1%: 12 ounces of 12.5% SH ($5-8), 2-4 ounces of surfactant ($2-4), tap water. Total: $7-12 per 5 gallons.

You save $65-90 per batch. Mixing supplies cost maybe $50 upfront. After the first batch, it’s pure savings.

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Pro Tips

Use warm water for mixing. Surfactant dissolves smoothly in warm water (around 90–100°F) instead of forming clumps. The temperature doesn’t affect cleaning power—it simply ensures proper mixing and uniform consistency. Avoid hot water over 100°F, as it accelerates SH degradation and increases fume release.

Mark your bucket clearly. “CHEMICALS ONLY - NO FOOD” with permanent marker. Include the mix ratio and date. Yes, people actually drink from chemical buckets if you’re not careful.

Pre-wet the surface with plain water first. Light mist, not soaking. Lets your chemical spread evenly instead of beading up and penetrates better.

Start with 1-gallon batches while you’re learning. Wasting 5 gallons hurts. Use the calculator to scale. Once you’ve dialed it in, go to 5-gallon batches.

Keep a mix log. Notebook or phone notes. Record the surface type, SH percentage, surfactant amount, dwell time, and how it turned out. After a few jobs you’ll have your own playbook and can stop guessing.

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Next Steps

Ready to mix like a pro?

• House Washing 101
• Sodium Hypochlorite Guide
• Surfactants Guide
• Pressure Washing Safety