Deck soft washing is the safest way to clean wood surfaces without splitting fibers or stripping finishes—but choosing the wrong method or contractor can still leave you with costly repairs. Knowing what to expect in terms of pricing, technique, and aftercare will help you hire the right professional and protect your investment. Let's break down what soft washing actually costs and how to prevent damage before it happens.
What Is Deck Soft Washing?
Soft washing uses low-pressure water combined with biodegradable cleaning solutions to remove algae, mold, mildew, and dirt from wood decks. Unlike pressure washing, which shoots water at 3,000+ PSI and can gouge or splinter wood, soft washing operates at 500 PSI or lower—or sometimes just gravity-fed spray with no pressure at all. The chemicals do the heavy lifting while water gently rinses everything away.
This approach is essential for cedar, pressure-treated lumber, and any stained or sealed deck. Professional soft washing respects wood while delivering thorough cleaning.
Typical Pricing for Deck Soft Washing
Cost varies by deck size, condition, and your region, but here's what to expect:
- Small decks (under 200 sq. ft.): $150–$300
- Medium decks (200–500 sq. ft.): $300–$600
- Large decks (500+ sq. ft.): $600–$1,200+
Most companies charge per square foot ($0.75–$2.50) or offer flat rates for common sizes. Additional fees apply if your deck has heavy mold, requires sealing afterward, or sits in a hard-to-access location. Get quotes from multiple providers—Mercoly makes it easy to compare trusted pressure and soft washing contractors in your area so you can see pricing side-by-side.
How Wood Damage Happens During Cleaning
The wrong cleaning method causes three main types of damage:
High-pressure damage. Pressure washers above 1,500 PSI can split wood grain, especially in softer species like cedar. Water is forced deep into the wood, raising grain and leaving permanent splintering.
Chemical burn. Overly strong cleaners or improper dwell time (how long chemicals sit on wood) can bleach, etch, or discolor the surface. Acidic solutions left too long eat through protective finishes.
Moisture trap. If the deck isn't properly dried after cleaning, water gets trapped under sealant or in joints, leading to rot, warping, and mildew regrowth within weeks.
Prevention: What to Ask Your Contractor
Before hiring, ask these specific questions:
- "What PSI will you use, and why?" (Answer should be under 1,500; many pros use 500 or less for wood.)
- "What cleaning solution do you use?" (It should be biodegradable and safe for plants/pets near runoff areas.)
- "How long will chemicals sit on the wood before rinsing?" (Typically 10–20 minutes for soft wash solutions.)
- "Will you dry the deck, and how?" (Air drying takes 24–48 hours; some pros use blowers to speed it up.)
- "Do you recommend sealing afterward?" (Many decks benefit from a fresh coat within 48 hours of cleaning.)
Reputable contractors will answer these without hesitation. If someone brushes off your questions, keep looking.
Post-Cleaning Care
After soft washing, your role matters:
- Wait 24–48 hours before walking heavily on the deck while it fully dries.
- Avoid sealing immediately. Most pros recommend waiting 48 hours so moisture escapes before you seal.
- Check joints and crevices. Wipe standing water from railings, steps, and gaps where moisture lingers.
- Inspect for remaining mold. A small amount of algae regrowth is normal; heavy regrowth within 2 weeks suggests incomplete cleaning or poor aftercare.
Plan for resealing every 2–3 years if you live in a wet climate, or every 3–4 years in drier areas. A fresh seal prevents dirt and moisture from embedding themselves and reduces how often you need cleaning.
When to Avoid Soft Washing Altogether
Some decks are too fragile or damaged for soft washing:
- Severely rotted wood (it needs replacement, not cleaning)
- Old pressure-treated lumber from the 1980s–1990s (arsenic-based treatments pose contamination risks if disturbed)
- Composite or synthetic decking (follow manufacturer guidelines; most allow soft wash only, not pressure)
If you're unsure about your deck's material or condition, ask a contractor for a free inspection first.
Frequently Asked Questions
Q: Is soft washing safe for composite decks? Most composite materials can handle soft washing at low pressure, but some brands are sensitive to certain chemicals—always verify with your deck's manufacturer specs before hiring.
Q: How often should I soft wash my deck? Once per year in humid climates, or every 1–2 years in drier regions; more frequent cleaning prevents deep mold buildup and reduces damage risk.
Q: Can I soft wash my deck myself? You can rent equipment, but improper technique with chemicals or pressure causes more damage than hiring a pro—professional-grade solutions and experience are worth the cost for wood preservation.
Compare quotes from certified contractors today and protect your deck investment.