How do I prepare a garage floor for epoxy coating in NB?

Properly preparing a garage floor for epoxy coating is 80% of the job — the coating itself goes on quickly, but inadequate surface preparation is the reason most epoxy coatings fail prematurely in NB garages. The concrete must be clean, open-pored, and dry for epoxy to bond reliably through NB's winters.

Step 1: Test for Moisture

Before anything else, test for moisture vapour emission. Tape a 2-foot square of plastic sheeting to the floor with all edges sealed, and leave it for 24–48 hours. Condensation on the underside means significant moisture is coming through the slab — a problem that must be addressed before epoxy, or the coating will delaminate. NB garages, particularly over basements or in areas with high water tables (Riverview, parts of Moncton), often have elevated moisture. New concrete must cure for at least 28–30 days in NB conditions before epoxy application — longer in cool weather.

Step 2: Clean Thoroughly

Remove oil stains using a concrete degreaser. Oil contamination is the second most common cause of epoxy failure — even old, invisible oil residue from a car parked for years will prevent proper adhesion. For fresh stains, apply degreaser, scrub with a stiff brush, rinse thoroughly, and allow to dry completely. For old, deep oil penetration, you may need to apply degreaser multiple times or accept that heavily contaminated spots won't hold epoxy as well as clean concrete.

Step 3: Open the Surface (Most Critical Step)

Epoxy does not bond to a smooth concrete surface — it needs a texture equivalent to 60-grit sandpaper (Concrete Surface Profile 2–3). There are two ways to achieve this:

Diamond grinding (professional method) — a floor grinder with diamond tooling physically removes the surface laitance and opens the concrete pores. This is the most reliable method and what professional NB coaters use. Equipment rental is available but requires skill to avoid grinding unevenly.

Acid etching (DIY method) — muriatic acid diluted in water (10% solution) etched onto the floor, scrubbed, neutralized with baking soda and water solution, rinsed thoroughly, then allowed to dry for 24 hours minimum. Acid etching works on porous concrete but is less effective on hard, dense concrete and does nothing on any previously sealed surface. It also generates fumes and requires proper PPE (chemical-resistant gloves, eye protection, respirator).

Do not coat over an existing painted or sealed floor without grinding — epoxy applied over existing coatings will peel with the old coating, not bond to the concrete.

Step 4: Fill Cracks and Holes

Fill cracks wider than 1/8 inch and any spalled areas with an epoxy crack filler or polyurea joint filler before coating. Allow to cure per product instructions.

Step 5: Apply in the Right Conditions

For NB garages: apply epoxy when floor temperature is between 10°C and 30°C, relative humidity is below 85%, and rising temperatures are expected (not falling — falling temperatures condense moisture on the floor). Avoid application on rainy days when humidity is high. Late spring through early fall is ideal in NB.

For DIY application, a two-car garage floor preparation takes a full day. The coating goes on the next day. New Brunswick Concrete can match you with professional floor coating contractors across NB if you prefer a guaranteed result with proper equipment.