Short answer: Yes, pressure washing is safe for interlock pavers — but only with low pressure, the right nozzle, and proper re-sanding afterward. High pressure destroys interlock joints and can cost $5,000-$15,000 to repair.
This guide covers the safe method, what damages interlock, and what to ask any contractor before they touch your driveway.
What Makes Interlock Vulnerable
Unlike poured concrete (one solid slab), interlock pavers are individual units held together by polymeric sand in the joints. This sand is the critical component — it locks pavers in place, prevents weed growth, and stops ant colonies.
High-pressure water blasts this sand out of the joints. Once the sand is gone:
- Pavers shift and settle unevenly
- Weeds grow aggressively in empty joints
- Ants build colonies under the pavers
- Water infiltrates the base, causing frost heave in winter
- Trip hazards form as pavers move
The Safe Method: Step by Step
Here's exactly how professional interlock cleaning should work:
Step 1: Pre-Treatment
Apply biodegradable cleaning solution to break down embedded dirt, algae, and organic staining. Let it dwell 10-15 minutes. This does most of the cleaning work before any pressure is applied.
Step 2: Weed Removal
Remove all visible weeds from joints before cleaning. If weeds are pressure-washed in place, root fragments remain and regrow faster.
Step 3: Low-Pressure Cleaning
| Setting | Safe Range | Danger Zone |
|---|---|---|
| PSI | 1,000-1,500 | 2,500+ (destroys joints) |
| Nozzle | 25° (green) or 40° (white) | 0° (red) or 15° (yellow) |
| Distance | 12-18 inches from surface | Under 6 inches |
| Angle | 45° to surface | 90° direct (blasts sand out) |
Step 4: Rinse and Dry
Thorough rinse to remove all cleaning solution and loosened debris. Allow joints to dry before re-sanding (critical — wet joints won't accept new sand properly).
Step 5: Polymeric Sand Re-Application
Sweep new polymeric sand into all joints. Vibrate or tamp to settle sand deeply. Mist with water to activate the polymer bonding agent. This is the step most DIYers and cheap contractors skip — and it's the most important.
Step 6 (Optional): Sealer Application
A clear paver sealer locks in the sand, enhances colour, and provides a barrier against future staining. Adds $200-$400 to the job but extends the clean appearance by 2-3 years.
What Damages Interlock (Common Mistakes)
| Mistake | What Happens | Repair Cost |
|---|---|---|
| Too high PSI (2,500+) | Sand blasted from joints immediately | $500-$1,500 (re-sand only) |
| Wrong nozzle (0° or 15°) | Concentrated stream cuts into sand and paver edges | $500-$2,000 |
| Too close (under 6") | Even low PSI damages at close range | $500-$1,500 |
| 90° angle (straight down) | Drives water into joints, blasts sand upward | $500-$1,500 |
| No re-sanding after | Joints empty, weeds in 2-4 weeks, pavers shift | $500-$1,500 (re-sand) to $5K-$15K (re-lay) |
| Rental machine (no PSI control) | Most rentals are 3,000+ PSI with no adjustment | $1,000-$15,000 |
Interlock Cleaning Pricing
| Service Level | What's Included | Price |
|---|---|---|
| Clean + Re-Sand | Low-pressure clean, weed removal, polymeric sand | $299 – $499 |
| Clean + Re-Sand + Seal | Above + clear paver sealer | $599 – $899 |
| Full Restoration | Deep clean + re-level pavers + re-sand + seal | $899 – $1,100+ |
GTA Interlock Hotspots
Some GTA areas have much higher interlock driveway density than others:
| Area | Interlock Density | Common Issues |
|---|---|---|
| Brampton (Castlemore, Springdale) | 🔴 Very High | New installs settling, salt damage, weed growth |
| Vaughan (Woodbridge, Kleinburg) | 🔴 Very High | Premium interlock, efflorescence, salt |
| Markham (newer areas) | 🟡 High | Mixed interlock + concrete, hard water staining |
| Richmond Hill | 🟡 High | Standard interlock, weed issues |
| Mississauga (Erin Mills, Churchill) | 🟡 High | Aging interlock, sand loss, settling |
| Oakville (south) | 🟡 Moderate-High | Premium stone, careful cleaning needed |
Questions to Ask Before Hiring
- "What PSI do you use on interlock?" — Correct answer: 1,000-1,500. Red flag: "Same as concrete" or "3,000."
- "Do you re-sand the joints?" — Correct answer: "Yes, with polymeric sand, included in the price." Red flag: "That's extra" or "Not necessary."
- "What nozzle tip?" — Correct answer: 25° or 40° fan. Red flag: Doesn't know or says "turbo nozzle."
- "Do you pre-treat?" — Correct answer: "Yes, with cleaning solution before pressure." Red flag: "We just blast it."
- "Are you insured?" — Correct answer: "$2M+ liability." Red flag: Hesitation or "working on it."
Safe Interlock Cleaning — Guaranteed
Low pressure. Proper re-sanding. No damage. Or you don't pay.
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