Preparing Your Site for Line Marking

A facility manager in Tullamarine called us last week, frustrated. Their new carpark lines were peeling after just four months. The previous contractor had painted over oil stains and existing degraded markings without proper preparation. What should have lasted 24 months failed in 16 weeks.

Surface preparation accounts for roughly 40% of a line marking project's success. Skip it, and you're wasting money on paint that won't adhere properly. Here's exactly how we prepare sites for long-lasting results.

Why Surface Preparation Matters

Line marking paint needs to mechanically bond with the substrate. Contaminants like oil, dirt, rubber deposits, and old failing paint create a barrier that prevents adhesion. Even invisible contaminants can cause problems.

We learned this lesson early. In 2012, we marked a warehouse floor in Campbellfield that looked perfectly clean. Within six months, lines were lifting in sheets. Testing revealed invisible silicone contamination from a previous floor sealer.

Step 1: Site Assessment

Before any cleaning begins, we conduct a thorough site assessment. This identifies potential issues that could affect adhesion and helps us plan the right preparation approach.

What We Check:

Surface type (concrete, asphalt, sealed concrete, epoxy-coated)
Existing line marking condition (can we paint over or must we remove?)
Oil and chemical contamination (visual inspection and water bead test)
Cracks, spalling, and surface damage requiring repair
Moisture content (must be below 6% for most applications)

Step 2: Removing Existing Line Markings

Old, degraded line markings must be removed before new paint is applied. Painting over failing markings is the number one cause of premature line marking failure.

When Removal Is Required:

Existing paint is peeling, flaking, or lifting
Multiple layers of old paint have built up (more than 2-3 layers)
Layout is changing (lines in different positions)
Incompatible paint types (e.g., applying waterborne over old solvent)

Step 3: Surface Cleaning

Once old markings are removed, the surface needs thorough cleaning to remove dirt, dust, oil, and other contaminants.

High-Pressure Water Cleaning

For most outdoor carparks, high-pressure water cleaning at 3,000-4,000 PSI removes surface dirt, loose material, and light contamination. This is our standard approach for routine repainting projects.

Degreasing for Oil Contamination

Oil stains require chemical degreasing before line marking. We use commercial alkaline degreasers, apply them to contaminated areas, scrub with stiff brushes, and rinse thoroughly. A truck depot in Somerton had diesel stains covering 30% of their carpark. Two degreasing cycles plus high-pressure cleaning were required.

Step 4: Surface Profiling

For optimal adhesion, concrete surfaces need a suitable profile (texture) for the paint to grip. Most line marking applications require CSP-2 to CSP-3 profile. This can be achieved through light mechanical abrasion using diamond grinding or shot blasting.

Step 5: Crack and Damage Repair

Cracks and surface damage should be repaired before line marking. Paint applied over cracks will fail along the crack lines as the substrate moves.

Crack Treatment Options:

Hairline cracks (under 1mm): Generally acceptable, no treatment required
Small cracks (1-3mm): Fill with flexible crack filler, allow to cure
Large cracks (3mm+): Route out, fill with appropriate repair compound

Step 6: Moisture Testing

Concrete and asphalt must be dry before line marking. Moisture trapped beneath paint causes blistering, peeling, and adhesion failure. We test moisture content using electronic moisture meters and require readings below 6% before application.

Step 7: Weather Conditions Check

Weather conditions directly affect paint curing and adhesion. We check conditions before every application and will postpone work if conditions aren't suitable.

Ideal Conditions:

Temperature: 10-35°C (surface and ambient)
Humidity: Below 85%
No rain forecast for minimum 4 hours after application
Surface temperature at least 3°C above dew point

Common Preparation Mistakes to Avoid

Painting over failing existing markings without removal
Skipping degreasing on oil-contaminated surfaces
Not allowing adequate drying time after cleaning
Applying paint in unsuitable weather conditions

Get a site assessment and preparation quote

Frequently Asked Questions

How long should I wait after rain before line marking?

Minimum 24 hours for outdoor concrete surfaces in summer, 48-72 hours in cooler months. We always test moisture content before application regardless of time elapsed.

Can you line mark over sealed concrete?

Yes, but the sealer must be compatible with the line marking paint, and the surface typically needs light profiling for adhesion. We test adhesion on sealed surfaces before committing to full application.

Preparing Your Site for Line Marking | Line Marking Australia Blog