Pressure Washing & Surface Prep
Professional pressure washing for driveways, siding, decks, and commercial surfaces
Overview
Pressure washing removes years of dirt, mildew, algae, oil stains, and oxidation from virtually any exterior surface. It is also the essential first step before any exterior painting, staining, or sealing project. The key is using the right pressure, nozzle, and technique for each surface -- too much pressure damages wood, stucco, and mortar; too little leaves surfaces dirty.
Denver's dry climate means less mildew overall compared to humid regions, but heavy growth concentrates on north-facing surfaces and shaded areas. Sprinkler overspray zones are the biggest mildew contributor in Denver. Intense UV causes oxidation buildup on siding and fading on painted surfaces.
Professional pressure washing uses a combination of high-pressure mechanical cleaning and low-pressure chemical cleaning (soft washing). Soft washing is essential for delicate surfaces like stucco, EIFS, painted wood, and roofing. Most jobs require both methods on different surfaces of the same property.
Materials & Tools Needed
Equipment
- Commercial gas pressure washer (3,000-4,000 PSI, 3.5-8 GPM)
- Surface cleaner attachment (16-24 inch spinning bar) for flat concrete
- Extension wands (12-24 ft telescoping) for multi-story reach
- Assorted spray nozzles (0, 15, 25, 40 degree) and downstream injector
Chemicals
- Sodium hypochlorite solution with surfactant for mildew/algae
- Concrete degreaser (sodium hydroxide based) for oil stains
- Wood cleaner and brightener (oxalic acid based)
- Efflorescence remover and neutralizing agents
Protection and Safety
- Chemical-resistant gloves, boots, and eye protection
- Plastic sheeting for plant and landscaping protection
- Caution/wet floor signage
Wastewater Management
- Containment berms and mats for environmental compliance
- Wet/dry vacuum or water reclamation system
- Portable pump for collecting chemical runoff
Step-by-Step Guide
Property Assessment
Identify all surfaces and their substrate type (concrete, vinyl, wood, stucco, brick). Document contamination type for each surface. Note delicate surfaces requiring soft washing.
Equipment Selection
Select PSI for each surface: 1,300-1,900 for delicate surfaces, 2,000-2,800 for wood and siding, 2,800-3,500 for concrete, 3,500+ for heavy commercial. Select appropriate nozzles.
Pre-Treatment and Protection
Pre-soak landscaping with clean water. Cover delicate plants. Close all windows and doors. Cover electrical outlets and light fixtures. Move outdoor items away from work areas.
Chemical Application
Apply cleaning solution from bottom to top on vertical surfaces to prevent streaking. Use appropriate chemicals for each contaminant: bleach solution for mildew, degreaser for oil, oxalic acid for rust.
Agitation
Scrub stubborn stains with brushes. Oil stains may need multiple degreaser applications. Use telescoping brush for second-story siding.
Hard Surface Washing
Use surface cleaner attachment on flat concrete for uniform results. Maintain 12-18 inch distance. Work in sections, rinsing downhill. Use appropriate pressure for brick and stone (1,500-2,500 PSI).
Siding Washing
Use 1,200-1,800 PSI for vinyl, 1,000-1,500 for wood and fiber cement, soft wash (under 500 PSI) for stucco. Always spray at a downward angle -- never aim under siding laps.
Deck and Fence Washing
Use 1,500-2,000 PSI max on softwood, up to 2,500 on hardwood. Always wash with wood grain. For deck prep before staining, apply wood brightener after cleaning.
Rinse and Neutralize
Rinse all surfaces top to bottom. Neutralize acid-treated areas. Re-rinse landscaping. Verify all soap residue is removed -- dried soap streaks are a common callback issue.
Post-Wash Inspection
Inspect for remaining stains, missed areas, and any damage. Re-treat stubborn areas. Verify window seals are dry and intact.
Wastewater Management
Contain and manage wastewater per Denver regulations. Chemical runoff cannot be discharged into storm drains. Collect for proper disposal.
Drying and Follow-Up
Allow 24-48 hours drying before painting, staining, or sealing. Inspect post-drying for issues not visible when wet. Provide recommendations for sealing or painting.
Denver Pro Tips
Denver's hard water leaves spots
Denver's moderately hard water (120-180 ppm) leaves mineral deposits on glass and dark surfaces. For final rinses on windows and high-end surfaces, use a water softener filter or deionized water rinse.
Freeze risk in shoulder seasons
Denver can freeze overnight as late as mid-May and as early as September. Water trapped in wood or stucco that freezes causes damage. Schedule so surfaces have full daylight to dry before temperatures drop below 35 degrees F.
Mildew concentrates on north faces and sprinkler zones
Denver's dry climate means less overall mildew, but growth concentrates on north-facing surfaces and sprinkler overspray zones. Recommend adjusting sprinkler heads away from siding and fences to prevent rapid regrowth.
Altitude reduces pump performance
Gas pressure washers lose approximately 3% power per 1,000 feet. At Denver altitude, expect 15-16% reduction. A 4,000 PSI unit may deliver only 3,400 PSI. Size equipment one class higher than sea level.
What Affects Pricing
- Total surface area to be cleaned
- Contamination level -- light annual cleaning vs. heavy mildew/oil remediation
- Surface type complexity -- single substrate vs. mixed requiring different PSI
- Chemical treatment requirements
- Access and logistics -- ground-level vs. multi-story requiring extension wands
- Wastewater containment requirements for commercial jobs
- Pre-paint prep scope -- cleaning only vs. cleaning + brightening + sanding
Frequently Asked Questions
Will pressure washing damage my surfaces?
How often should I pressure wash?
What is the difference between pressure washing and soft washing?
Will it remove paint or stain from my deck?
How We Can Help
Professional pressure washing & surface prep is complex work that benefits from experience, proper equipment, and knowledge of Denver's unique climate conditions.
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