Most interlock that looks tired in Stittsville, Kanata and the rest of west Ottawa does not need replacing. It needs reading. A dip by the garage, a hump in the middle of the patio, a border that has wandered into the lawn and a white haze on brand-new pavers are four different problems with four different fixes, and one of them is not a problem at all.
This is the repair guide. If you are planning new interlock, our interlocking guide for Stittsville covers patios, walkways and driveways from the base up.
Why interlock is worth repairing
Asphalt and poured concrete get cut and patched, and the patch shows forever. Interlock comes apart. Unilock’s paver maintenance guide describes the utility-repair procedure in six steps: lift the pavers over the area plus about 0.5 m (18 in) on each side, dig and repair, refill and compact the base, relevel the bedding, relay the pavers and compact, then refill the joints. Every repair below is a variation on that.
Reading the surface: six common problems
1. A low strip along the house, garage or step
This is the most common repair we see. Unilock notes that settlement is “commonly found adjacent to buildings or curbing where it is difficult for the installer to adequately compact the base material.” On newer Stittsville and Kanata homes there is a second cause: the soil backfilled against the foundation keeps consolidating for years after the builder leaves.
The fix: lift the strip, rebuild and compact the base in lifts, and relay with the surface sloping away from the wall. If the dip is more than 40 mm (1-1/2 in), the correction goes into the base. Unilock is explicit that you should not relevel by adding bedding sand alone.
2. A dip out in the open
When settlement shows up away from walls, Unilock lists three usual causes: water held in the base, bedding or joint sand that has washed out, or loose edge restraint letting the pavers drift apart. A dip under a downspout outlet is a classic example. So is a dip where a gas or cable line was trenched before the patio went down.
The fix: the same lift-and-relay, but the cause has to be fixed too. That might mean moving the downspout, adding drainage under the base or rebuilding a failed edge. Otherwise the dip comes back.
3. A hump that appeared over winter
An upward bulge is swell, and Unilock attributes it to frost action in the subgrade or swelling soil. On the clay that underlies much of Stittsville and Barrhaven, that usually means water is getting into the base and freezing. Our guide to patio base depth in Ottawa’s freeze-thaw climate explains why.
The fix: lift the area to find the cause. It is often a thin base, a spot where water collects, or fine material that holds water. Correct it, relevel the base and relay. If the whole surface heaves, see “When it is a rebuild” below.
4. Edges spreading, joints opening
Interlock holds together because each paver is locked by its neighbours, and the outer row is held by an edge restraint: a concrete curb, a buried plastic or aluminum edge spiked into the base, or a soldier course set in concrete. When the restraint fails, the border creeps outward, joints widen, sand washes out and the field starts to move.
On driveways there is a related problem Unilock calls horizontal creeping: where cars brake, accelerate or turn, the joint lines bend in the direction of the wheels. Mild creeping is managed by keeping the joints topped up. Severe creeping means lifting back to stable joints, relaying and recompacting.
The fix: reinstall or replace the edge restraint, pull the border back into line and refill the joints. The restraint is the cause; the open joints are the symptom, and a repair has to deal with both.
5. Weeds, ants and empty joints
Unilock’s advice is simple: “The best strategy to prevent weeds is to keep paver joints full.” When joints empty out, windblown seeds lodge and germinate. Ants move into the sand for the same reason.
The fix: clean the joints out, check for movement underneath, then refill with a polymeric sand or another stabilised jointing material. Polymeric sand hardens once wetted and stays flexible enough to accept freeze-thaw movement. Applying it to dry joints in dry weather is most of what makes it work.
6. A white haze on new pavers
That is efflorescence, and it is not a defect. Unilock describes it as a naturally occurring calcium salt that “does not affect the structural integrity of concrete” and “typically disappears with no further intervention after a season of rainfall.” If you want it gone sooner, Unilock’s efflorescence guide recommends dish soap, water and a stiff plastic brush (never a wire brush, which leaves rust marks), or an efflorescence remover tested on a hidden spot first. Pavers must be clear of it before any sealer goes on.
When it is a rebuild, not a repair
Relaying pavers over a bad base buys two or three winters. A rebuild is the honest answer when:
- the whole surface undulates, not one area,
- water sits on it after rain, or runs toward the house, or
- the base, once a test section is opened, turns out to be a few inches of stone dust on clay.
A rebuild means excavating to the depth your soil needs, laying geotextile, placing new granular base in compacted lifts and relaying. Often the original pavers can be cleaned and reused, which keeps the cost down and the look unchanged. In Kanata North, where bedrock can sit close to the surface near the Carp Hills, the base is sometimes built up rather than dug down.
Winter: the season that does the damage
Ottawa winters cause a lot of interlock damage that gets blamed on installation. Unilock’s guide is specific:
- Plows and blades. Metal blades can chip pavers and leave rust marks. Unilock recommends fitting blades with shoes or high-density plastic edges, or using a non-metal rotary snow broom.
- De-icers. Unilock lists rock salt for temperatures down to about −7 °C and calcium chloride, used sparingly, below that. It says not to use magnesium chloride, calcium magnesium acetate, potassium chloride, potassium acetate or fertilisers containing ammonium nitrate or ammonium sulfate, which “rapidly attack and disintegrate concrete.” Sweep up the excess after a melt and wash the surface in spring.
If your driveway is chipped along the plow line, that is the blade, not the base.
Sealing: optional, cosmetic, not a fix
Unilock says its pavers “do not require sealing to maintain their structural integrity.” Sealer can deepen colour, add sheen and make stains easier to lift, but one applied after installation generally needs redoing every two or three years, and applying it too often leaves a milky haze. It does nothing for a surface that is moving.
Driveways and the City’s right of way
The part of your driveway between the sidewalk (or curb) and the road is in the City’s right of way. The City’s Landscaping Education Guide says an access or road cut permit is not needed when resurfacing a driveway with no change to its size or slope. Widening it, changing its slope or rebuilding the apron is another matter. If the repair is turning into a redesign, see what an interlock driveway costs in Ottawa.
Two more rules apply to repairs as much as to new work. Provincial law requires locates through Ontario One Call before digging, and the City’s hardscaping contractor licence, required since March 1, 2026, covers businesses that install or reconstruct hard surfaces. A repair contractor needs it too.
What drives the cost of a repair
We do not publish a per-square-foot repair price, because two repairs of the same size can be very different jobs. What moves the number:
- Area and access. A strip along a garage is quicker than a patio behind a fence with no machine access.
- Base depth to correct. Relevelling bedding is quick. Rebuilding base in lifts takes longer.
- The cause. Moving a downspout or adding drainage adds a line; ignoring it means paying again.
- Paver condition. Most pavers can be reused. Broken units need matching, and discontinued colours sometimes mean borrowing pavers from a hidden area.
- Joint material. Polymeric sand versus a premium jointing compound.
For full replacement pricing, our interlocking patio cost guide sets out published Ottawa ranges.
Interlock repair in Stittsville, Kanata and west Ottawa
We repair and rebuild interlock patios, walkways, steps and driveways across Stittsville, Kanata, Barrhaven and Nepean. We are a licensed City of Ottawa hardscaping contractor, TechoPro certified and a Techo-Bloc authorized contractor, a Permacon installer partner, and our crew is Unilock trained. The full scope is on our hardscaping page. If the problem is water coming off the lot rather than the pavers themselves, see yard drainage and erosion control in Nepean.
Book a free on-site estimate. We will lift a test section if we need to, tell you whether it is a relay or a rebuild, and give you a fixed price for the one you actually need.
Published October 25, 2026 by ALM Construction & Landscaping. General information for Ottawa-area homeowners, not a substitute for the City's determination on your specific project.