Should I repair the cracks in my garage floor before getting it coated or will the coating fill them?

You absolutely need to repair cracks before coating your garage floor. A coating is not a crack filler, and applying epoxy or polyaspartic over unrepaired cracks will not make them go away. The coating will follow the contour of the crack, and within a few months the crack will telegraph right through the coating and often cause it to peel or chip along the crack line.

Ottawa garage floors are especially prone to cracking because of our extreme freeze-thaw cycles. The ground under your slab freezes deeply in winter and heaves, then settles again in spring, and over the years this movement creates cracks ranging from hairline to half an inch or wider. Road salt tracked in from your car accelerates the problem because salt water penetrates existing cracks, freezes inside them, and forces them wider with each cycle.

The type of repair depends on the type of crack. Hairline cracks under an eighth of an inch can be addressed during the grinding or shot blasting phase of floor preparation. The grinding process opens these tiny cracks slightly, and the primer coat of your coating system flows into them and effectively seals them. No separate repair step is needed for these.

Small to medium cracks between an eighth of an inch and a quarter inch need to be filled with a flexible crack filler or a polyurea joint filler. These products remain slightly flexible after curing, which is important because concrete continues to move with temperature changes. A rigid filler in a moving crack will just crack again. Most Ottawa coating contractors include this level of crack repair in their standard preparation process at no extra charge or for a modest upcharge of $100 to $300.

Larger cracks over a quarter inch, and especially any cracks where one side is higher than the other, require more involved repair. The crack needs to be routed out with a grinder to create a clean channel, filled with an appropriate repair material, and then ground flush with the surrounding floor. If slabs have shifted and there is a lip between sections, that needs to be ground down to create a smooth transition. This type of repair can add $300 to $800 to your project depending on the extent of the damage.

Spalling, which is the flaking and pitting that salt damage causes on the surface, also needs to be addressed before coating. Small areas of spalling can be filled with a cementitious patching compound or an epoxy mortar. Larger spalled areas might need a skim coat to build the surface back up to a level plane. In severe cases where the spalling covers a significant portion of the floor, your contractor may recommend a self-leveling overlay before the coating goes on, which can add $1,000 to $2,000 to the project but gives you a perfectly smooth surface.

The key takeaway is that any reputable Ottawa coating contractor will thoroughly assess your floor condition and address all cracks and damage as part of the preparation phase. Be wary of any contractor who says they can just coat right over cracks and damage. Proper preparation is what separates a coating that lasts ten years from one that fails in two, and in Ottawa's harsh climate, cutting corners on prep is a guaranteed path to early failure.

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Looking for experienced contractors? The Ottawa Construction Network connects Ottawa homeowners with qualified professionals:

• 613Bins
• RenoMotion Inc.
• ALM Construction & Landscaping Inc.
• Titley Construction
• ARTEXPRO Tile & Finishes