Power washing is a powerful tool for cleaning grime, dirt, and mold from almost any surface. But with great power… comes the potential for serious damage if used incorrectly. 💥
While pressure washers are amazing on siding, concrete, decks, and fences, there are some surfaces you should never — or only very carefully — power wash. Whether you’re a homeowner or a professional, knowing what not to power wash can save you from costly repairs, unhappy customers, or even safety hazards.
In this article, we’ll explore the top materials and areas you should steer clear of — or approach with extra caution — when using high-pressure water. 🧠💧
🏠 1. Asphalt Roof Shingles
Let’s start with one of the biggest power washing mistakes people make: spraying the roof.
Why Not?
- Shingles are made with protective granules that can be stripped away with high pressure.
- Removing granules shortens the roof’s lifespan and voids warranties.
- Water can get underneath shingles, leading to rot, leaks, or mold. 😬
Safer Alternative:
Use a soft wash method — low-pressure rinse with roof-safe chemicals designed to kill moss, algae, and mildew. 🧴
🧱 2. Old Brick or Mortar
Brick is tough — but not indestructible. Older brick structures with crumbling mortar are especially vulnerable.
What Can Go Wrong?
- High-pressure spray can erode mortar joints.
- Loose bricks may dislodge.
- Water can seep into cracks, freeze, and cause further damage.
What to Do:
If you must clean brick, use:
- A low-pressure setting (under 1,000 PSI)
- A 40° white tip
- Detergents that loosen dirt before rinsing
⚠️ Always inspect the brick condition first.
🪵 3. Weathered or Painted Wood
Wood surfaces, especially if older or untreated, can suffer from too much pressure.
Risky Results:
- Splintering and gouging the surface
- Peeling paint or stain
- For decks: damaging structural integrity over time
Safer Method:
- Use low pressure (under 1,500 PSI)
- Spray with the grain
- Keep the wand at least 12 inches away
- Soft wash painted surfaces instead 🎨
🖼️ 4. Windows and Glass Panels
Tempted to blast those dirty windows? Think again.
Here’s Why:
- High pressure can crack or shatter glass
- It may break seals in double-pane windows, causing fogging
- Water can be forced into window frames, leading to rot or mold
💡 Use a soft cloth or a hose with a squeegee for window washing. For high-up areas, consider a professional window cleaning tool.
🪞 5. Vents, Openings, and Electrical Panels
When cleaning a house exterior, it’s easy to overlook:
- Dryer vents
- Electrical boxes
- Outdoor outlets
- HVAC units
- Light fixtures
But these areas are not designed to get soaked under pressure.
What Can Happen:
- Water intrusion in electrical areas = ⚡ fire hazard or short circuit
- Dryer vent damage = reduced airflow or mold buildup
- Soaked insulation inside walls
✅ Cover these areas before washing, or work around them with low pressure.
🪟 6. Fiber Cement Siding
Fiber cement is durable, but manufacturers (like James Hardie) recommend against pressure washing with high PSI.
Why?
- Excessive pressure can dislodge caulking, allowing water to seep behind panels
- Surface paint can chip or fade prematurely
- It voids many warranties 📝
Safer choice: soft washing with detergent, gentle rinse, and scrub brushes as needed.
🚪 7. Wood Furniture and Wicker
It may be tempting to blast that grimy patio set — but power washing delicate outdoor furniture can lead to splintering, peeling, and broken frames.
Damage Risks:
- Wicker and rattan = disintegrate under pressure
- Wooden chairs/tables = splinter, warp, or lose finish
- Screws and fasteners may loosen
🪑 Use a garden hose or low-pressure rinse instead, followed by scrubbing and sealant reapplication.
🖼️ 8. Antique or Decorative Items
Fountains, statues, planters, garden gnomes — anything decorative or fragile should be cleaned by hand.
High pressure can:
- Chip paint
- Crack ceramic or stone
- Damage hand-painted or delicate finishes
✨ Treat these items like art — because they often are.
🐾 9. Surfaces with Loose or Damaged Paint
If your goal isn’t paint removal, do not power wash:
- Fences with flaking paint
- Siding with bubbled or cracked coatings
- Painted metal with visible rust
The force will strip away more than you want and may create uneven patches or expose bare material underneath.
🎨 Sanding and repainting may be required after high-pressure cleaning.
🏠 10. Interior Use (Never!)
Last but definitely not least: NEVER use a power washer inside your home. It may seem obvious, but accidents have happened.
Why not?
- Risk of flooding walls, floors, or insulation
- Can damage appliances, wiring, drywall
- Can lead to mold and mildew growth
🛑 Just don’t do it.
✅ Final Tips: How to Stay Safe
To avoid damage:
- Always start with the lowest pressure setting
- Test a small hidden area first
- Keep the nozzle 12–24 inches away from the surface
- Use appropriate detergents for the material
- Consider soft washing when in doubt
📸 Take before-and-after photos and inspect the surface after cleaning — it’s the best way to learn and improve.
🎯 Final Thoughts
Power washing is a powerful cleaning method, but it’s not a one-size-fits-all solution. Knowing what NOT to wash — or how to do it safely — can save you:
- Time
- Money
- Client complaints
- Unintended damage
If you’re unsure, err on the side of caution and soft wash or consult a pro. Your property (and your customers) will thank you. 🙏💧
