In Ontario, “surface preparation” isn’t just about cleaning; it’s a rigorous legal and technical requirement designed to ensure the longevity of infrastructure and the safety of the public. Whether you are a contractor or a property owner, adhering to these standards prevents premature failure and costly rework.
1. The Gold Standard: OPSS
The Ontario Provincial Standard Specifications (OPSS) are the primary guidelines used by the Ministry of Transportation (MTO) and municipalities.
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OPSS 310: Covers the construction of hot mix asphalt. It dictates that the underlying surface must be free of standing water, dust, and loose aggregate before any tack coat or asphalt is applied.
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OPSS 351: Governs the removal and preparation for concrete sidewalks and curbs.
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The “Clean & Dry” Rule: Almost all provincial standards mandate that surfaces must be “clean, dry, and free of deleterious material” before any coating or repair is initiated.
2. Preparation Methods by Surface Type
Different surfaces require specific mechanical or chemical interventions to meet Ontario building codes.
| Surface | Common Prep Standard | Key Requirement |
| Concrete (New) | CSP 3-5 (ICRI Guidelines) | Removing “laitance” (the weak top layer) via shot-blasting or grinding. |
| Asphalt (Repair) | OPSS 310 / 331 | Milling or routing cracks to a specific width/depth ratio before sealing. |
| Industrial Floors | ASTM D4259 | Mechanical abrasion to ensure a “profile” that allows epoxy to bond. |
3. Accessibility Standards (AODA)
In Ontario, surface preparation for public-facing areas must also comply with the Accessibility for Ontarians with Disabilities Act (AODA).
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Firmness & Stability: Surfaces must be prepared to be firm, stable, and slip-resistant.
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Changes in Level: Any vertical change in a surface greater than 6 mm must be beveled or repaired to prevent tripping hazards for those using mobility devices.
4. Environmental & Safety Regulations
Ontario’s Ministry of the Environment, Conservation and Parks (MECP) regulates how you handle the waste generated during preparation.
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Dust Control: Dry grinding or shot-blasting requires HEPA-filtered vacuums to prevent silica dust—a major health hazard under Ontario’s Occupational Health and Safety Act (OHSA).
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Wash Water: If using pressure washing or acid etching, you cannot allow the runoff to enter storm drains or “watercourses” (Environment Protection Act).
Expert Tip: In Ontario, “Good Workmanship” is a legal term under O. Reg. 517/06. If a repair fails because the surface wasn’t properly prepared (e.g., painting over oily concrete), the contractor can be held liable for not following “accepted trade standards.”
