You’ve seen it before: those stubborn weeds pushing up through the joints of your beautiful interlock paving. You pull them out, sweep the area clean, maybe even apply some weed killer—and within weeks, they’re back. If you’re tired of fighting the same battle every spring and summer, you’re not alone. Weeds in interlock joints are one of the most common complaints we hear from Ottawa homeowners.
The good news? There’s a proper, permanent solution. But first, let’s understand why those weeds keep coming back, and why quick fixes only make the problem worse.
Why Do Weeds Grow in Interlock Joints?
Interlock pavers are designed with small gaps (joints) between each stone. These joints serve an important purpose: they allow for drainage, prevent cracking from ground movement, and give the pavement flexibility during freeze-thaw cycles—critical in Ottawa’s climate.
However, when these joints aren’t properly filled and sealed, they become the perfect environment for weed growth. Here’s why:
1. Empty or Degraded Joint Sand
Most interlock installations use regular masonry sand or “jointing sand” to fill the gaps between pavers. Over time, this sand washes away from rain, gets blown out by wind, or simply settles and compacts from foot traffic and vehicle weight. Empty joints create pockets where weed seeds, carried by wind or birds, can settle and germinate.
2. Organic Matter Accumulation
Leaves, grass clippings, dirt, and other organic debris settle into the joints between pavers. As this material decomposes, it creates nutrient-rich soil—essentially a mini garden bed—perfect for weed seeds to take root. Even a thin layer of decomposed organic matter is enough to support aggressive weed species like dandelions, crabgrass, and clover.
3. Moisture Retention
While proper drainage is essential for interlock longevity, joints filled with regular sand can retain just enough moisture to support plant growth without draining properly. This creates ideal conditions for germination, especially during Ottawa’s wet spring months.
4. Sun Exposure and Temperature
The dark color of most interlock pavers absorbs heat, warming the sand in the joints. This warmth, combined with moisture and organic matter, accelerates seed germination. Driveways and patios get full sun exposure, making them prime real estate for hardy weed species.
Temporary Fixes: Why They Don’t Last
When weeds appear, most homeowners try one or more of these common “solutions.” While they may provide short-term relief, none address the root cause of the problem.
Hand Pulling
Pulling weeds by hand removes what you see above ground, but rarely gets the entire root system. Perennial weeds like dandelions have deep taproots that break off when pulled, allowing the plant to regenerate. You’ll be pulling the same weeds again in 2-3 weeks.
Chemical Weed Killers
Herbicides kill existing weeds but do nothing to prevent new seeds from germinating. They also introduce chemicals into your yard that can affect pets, children, and beneficial insects. In Ottawa, where many properties are near waterways, chemical runoff is an environmental concern. Plus, once the dead weeds are gone, the empty joints remain—ready to host the next generation.
Vinegar or Boiling Water
Natural alternatives like vinegar or boiling water can kill weeds on contact, but like chemical herbicides, they’re only treating symptoms. The joints remain vulnerable, and new weeds will appear as soon as more seeds arrive.
Regular Sand Refill
Simply sweeping fresh sand into the joints is marginally better than leaving them empty, but regular masonry sand offers no weed resistance. It will wash out again with the next heavy rain, and any seeds already in the joints will germinate right through it.
The Permanent Solution: Proper Polymeric Sand Installation
If you want to stop weeds from returning year after year, you need to eliminate the conditions that allow them to grow. That’s where polymeric sand installation comes in.
Unlike regular jointing sand, polymeric sand contains special additives and binding agents. When properly installed and activated with water, these polymers create a solid, semi-flexible bond between the sand particles. This creates a barrier that:
- Prevents weed growth by eliminating the loose, nutrient-rich environment weeds need
- Resists erosion from rain, sprinklers, and power washing
- Deters insect colonization, particularly ants that can destabilize pavers
- Maintains joint stability while still allowing proper drainage and flexibility
- Lasts for years with minimal maintenance, unlike regular sand
For a deep dive into how polymeric sand works and what to expect, check out our complete polymeric sand guide for Ottawa homeowners.
How Polymeric Sand Installation Works
Proper polymeric sand installation isn’t just about dumping a bag and calling it done. There’s a specific process that must be followed for long-lasting results:
Step 1: Complete Joint Cleaning
All existing sand, weeds, roots, and debris must be completely removed from the joints. We use specialized tools to extract old material down to the compacted base layer. This is critical—polymeric sand won’t bond properly if there’s contamination in the joints. Professional interlock cleaning ensures the surface and joints are pristine before installation.
Step 2: Surface Preparation and Repairs
Any damaged, sunken, or lifted pavers should be repaired before installing polymeric sand. If your interlock has structural issues like settling or lippage (uneven pavers), now is the time to address them. Learn more about when repairs are needed in our guide on interlock repair solutions.
Step 3: Polymeric Sand Application
The polymeric sand is carefully swept into the joints, ensuring complete fill from the base to approximately 1/8 inch below the paver surface (the chamfer line). Overfilling or underfilling can compromise the bond and longevity of the installation.
Step 4: Compaction and Excess Removal
The surface is thoroughly cleaned to remove all loose sand from the paver faces. Any residue left behind will bond to the stone surface during activation, creating a hazy film that’s difficult to remove later.
Step 5: Water Activation
Using a fine mist, the polymeric sand is carefully activated. Too much water can wash out the polymers; too little won’t activate the bonding agents. The water penetrates the joints and triggers the chemical reaction that binds the sand particles together.
Step 6: Curing Period
The installation must cure for 24-48 hours without disturbance. During this time, the area should be kept dry and free from foot traffic or vehicle use. Once cured, the polymeric sand forms a durable, semi-flexible joint fill that will protect your interlock for years.
What About DIY Polymeric Sand Installation?
We understand the appeal of tackling this project yourself. Polymeric sand is available at most home improvement stores, and the process might seem straightforward. However, there are significant risks:
- Improper joint cleaning: Contaminated joints won’t bond properly, leading to premature failure
- Incorrect water activation: This is the most common DIY mistake and can ruin an entire installation
- Surface residue: Polymer haze on paver surfaces requires professional cleaning equipment to remove
- Weather timing: Temperature and moisture conditions must be right for proper curing
- Product selection: Different polymeric sand formulations work better for different joint widths and paver types
A failed DIY installation often costs more to fix than hiring professionals from the start. You’ll need to remove the failed polymeric sand (which is much harder than regular sand), clean the joints again, and start over—this time with less material to work with if pavers were damaged in the process.
Long-Term Maintenance After Polymeric Sand Installation
Once your polymeric sand is properly installed, maintenance becomes far easier. Here’s what you can expect:
- Annual cleaning: A simple sweep or gentle power wash (using proper technique) keeps the surface looking great
- Rare weed appearance: You might occasionally see a weed seed try to germinate on top of the polymeric sand, but it won’t take root and can be easily brushed away
- Joint inspection: Every 2-3 years, check for any areas where joints may need minor top-up due to extreme weather or settling
- Expected lifespan: With proper installation, polymeric sand typically lasts 10-15 years in Ottawa’s climate
Ottawa’s Climate and Polymeric Sand Performance
Ottawa’s extreme temperature swings—from -30°C winters to +30°C summers—make it especially important to use high-quality polymeric sand designed for freeze-thaw cycles. Not all polymeric sand products are created equal.
We’ve installed polymeric sand on countless driveways, patios, and walkways across Ottawa, from Stittsville to Gloucester, and can recommend the right product for your specific installation. Factors like joint width, paver type, sun exposure, and drainage all influence which polymeric sand formulation will perform best.
When to Consider Professional Polymeric Sand Installation
If your interlock is more than 5 years old and you’ve never had polymeric sand installed—or if it’s been 10+ years since the last installation—it’s likely time for service. Other signs include:
- Persistent weed growth despite regular maintenance
- Visible joint erosion or missing sand
- Ant colonies disturbing the sand between pavers
- Pavers becoming loose or shifting
- You’ve recently had repairs done and need to reseal the joints
Ready to Say Goodbye to Weeds for Good?
Stop wasting your weekends pulling weeds and fighting a losing battle. Professional polymeric sand installation is a one-time investment that protects your interlock, preserves its beauty, and eliminates the frustration of recurring weed growth.
At Interlock Experts, we’ve helped hundreds of homeowners across the city solve their weed problems permanently. Our team uses premium polymeric sand products, follows manufacturer specifications precisely, and guarantees our installations.
Contact us today for a free quote on polymeric sand installation. We’ll assess your interlock, recommend the best solution for your specific situation, and provide a detailed estimate with no obligation. Your weed-free interlock is just one phone call away.
Serving Ottawa and surrounding areas including Kanata, Barrhaven, Orleans, Nepean, Stittsville, Gloucester, Manotick, and Riverside South.