Ottawa relies heavily on road salt to keep streets safe through a long winter, and a surprising amount of it ends up in your driveway. Every time you pull in, your car drops salty slush from its wheel wells onto the concrete or interlock. By April, you may notice white chalky stains, crumbling paver edges, and loose, weedy joints.
Here's what's happening, and how to stop it.
How salt attacks concrete and interlock
1. Crystallization pressure
When salt dissolves in melting snow, the salty water soaks into the tiny pores in concrete and pavers. As it dries, the salt re-crystallizes inside those pores. The growing crystals push outward and, over time, flake off the surface. This is called spalling, and it's why older driveways get a pitted, rough texture.
2. More freeze-thaw cycles
Salt lowers the freezing point of water, so instead of freezing once and staying frozen, water in your driveway melts and refreezes many more times over the winter. Water expands about 9% when it freezes, so every cycle widens existing micro-cracks a little more.
3. Joint sand breakdown
The sand between interlock pavers holds them in place. Salt and constant moisture wash out and weaken that sand, especially older non-polymeric sand. Once the joints open up, pavers shift, and weeds and moss move in as early as May.
Why a garden hose isn't enough
Rinsing with a hose moves surface salt around but often pushes it deeper into the joints. It also can't lift the grime and algae bonded to the surface over the winter.
What professional power washing does
- Flushes salt out of the surface and joints using a rotary surface cleaner that applies even pressure without leaving stripes or gouging pavers.
- Removes moss, weeds, and grime from paver joints, down to the base.
- Treats oil and rust stains before washing, so they lift more completely.
- Prepares for re-sanding. Once the pavers are dry, polymeric sand is swept into the joints and activated. It hardens to lock pavers together and resists weeds, ants, and future salt wash-out.
When to do it
The best time is late April to June, once overnight temperatures stay above freezing and the salt season is over. Doing it every spring is one of the most cost-effective ways to protect a driveway or patio that cost thousands to install. For more on timing, see the best time to power wash your home in Ottawa.
Book your spring wash
AV Group provides driveway and interlock power washing across Ottawa, including Kanata, Nepean, and Orléans. Pair it with window cleaning for a full spring refresh.