Why Your Pavers Sink After Every Ottawa Winter.

Every April, Ottawa driveways tell the same story: ruts where the car sits, a dip by the garage, edges creeping outward, and weeds in the joints. It is not bad luck, and it is not the pavers. It is physics — and it was decided the day the base was installed.

What Ottawa freeze-thaw actually does

Ottawa cycles above and below freezing more than 60 times in a typical winter. Each cycle works the same way: water sitting in the soil under your driveway freezes, expands by about 9%, and lifts everything above it. When it thaws, the surface settles back — but never quite evenly. Multiply that by 60 cycles and a few winters, and a shallow base turns into a roller coaster.

Our clay-rich soil makes it worse. Clay holds water instead of draining it, which means there is always moisture available to freeze. Clay can heave four to six inches between November and April — that is the force your base has to absorb.

Why shallow bases fail first

Frost in Ottawa penetrates well past 4 feet in a cold snap. No residential base goes that deep — so the strategy is not depth alone, it is drainage. A properly built base uses 8-12 inches of HPB (high-performance bedding) limestone, an open-graded stone that lets meltwater drain through instead of sitting under your pavers. No water, no ice lens, no heave.

A 4-inch "base" — often just screenings thrown on soil — does the opposite. It holds water like a sponge. The first winter moves it; the third winter makes it obvious.

The five signs your base is the problem

• Car ruts — two parallel dips where your wheels track. The base is thinnest or least compacted there.
• Birdbaths — water pooling after rain means the surface has settled below drainage pitch.
• Creeping edges — border pavers spreading outward means the edge restraint failed, not the pavers.
• Weeds and ant hills — joints full of organic dust instead of polymeric sand. Weeds root in the joint, not under the paver.
• A step or lip at the garage — the driveway settled but the garage slab, on a proper foundation, did not.

What a Zone 5a base looks like

• Excavation to 8-12 inches depending on use (walkways 8, patios 10, driveways 12)
• Woven geotextile fabric separating soil from stone
• HPB limestone compacted in 4-inch lifts with a plate compactor
• Concrete haunch or spiked aluminum edge restraint
• Polymeric sand swept into joints and hardened

If your driveway is already sinking, you usually do not need a new one. Lift, re-base and re-lay keeps your existing pavers and fixes the actual problem at a fraction of replacement cost. Not sure which you need? Book a free assessment.