Eliminate Weeds from Concrete Cracks: A DIY Guide

Weeds growing in the cracks of your driveway or sidewalk can be frustrating. No matter how many times you pull them out or spray them with herbicide, they always seem to return. This recurring issue happens because the cracks in concrete provide the perfect environment for weed growth. If you’re tired of dealing with these unwanted plants, this guide will walk you through both temporary and permanent solutions to keep your driveway and sidewalk weed-free.

Understanding the Problem: Why Do Weeds Grow in Concrete Cracks?

Before jumping into solutions, it's important to understand why weeds thrive in concrete cracks and expansion joints. These cracks may seem like tough, barren spaces, but they actually create ideal conditions for weeds to sprout and grow.

Common Causes of Weed Growth in Concrete Cracks

• Soil Accumulation: Over time, dirt, dust, and organic matter settle into the cracks, creating a fertile environment for seeds to germinate.

• Moisture Retention: Rainwater and irrigation seep into these gaps, providing the moisture necessary for plant growth.

• Sunlight Exposure: Unlike weeds in shaded garden beds, weeds in concrete cracks receive full sun, accelerating their growth.

• Seed Dispersal: Weed seeds are lightweight and can easily be carried by the wind or by foot traffic, settling into the cracks and taking root.

The Challenge of Weed Removal

Many people try pulling weeds by hand or spraying them with herbicides, but these methods only provide short-term relief. Most weeds have deep roots that remain embedded in the soil beneath the concrete, allowing them to regrow quickly. If you’re serious about eliminating these pesky plants, you need a more effective approach.

Temporary Solution: Using Preen Granules for Weed Prevention

If you’re looking for a quick and easy way to prevent weeds from growing in concrete cracks, using Preen granules can be an effective short-term solution. Preen is a pre-emergent herbicide that stops weed seeds from sprouting, providing a protective barrier that lasts for months.

Step-by-Step Application of Preen Granules

1. Clear the Area: Begin by removing any existing weeds and debris from the cracks. Pull weeds out by hand, use a flathead screwdriver, or trim them down with a string trimmer to extract as much of the root as possible.

2. Rinse Thoroughly: Use a garden hose to flush out any remaining dirt, dust, or loose weed roots from the cracks. Aim to clean at least a couple of inches below the surface to ensure thorough removal.

3. Let It Dry: Allow the area to dry completely before proceeding to the next step. This helps the granules adhere to the cracks more effectively.

4. Apply Preen Granules: Evenly sprinkle Preen into the cleaned cracks and expansion joints. The granules create a chemical barrier that prevents new weeds from sprouting.

5. Monitor the Area: This method provides protection for approximately six months. However, rain, wind, and natural debris accumulation can introduce new soil into the cracks, which may allow new weeds to grow over time.

While Preen granules are a great short-term fix, they do not permanently seal the cracks. If you want a long-term solution that eliminates weeds for good, consider sealing the expansion joints properly.

Natural Methods to Keep Weeds Away

If you prefer a more natural approach to weed control, here are a few additional methods to consider:

• Boiling Water: Pouring boiling water directly into cracks can kill weeds and their roots instantly. This method is best for smaller infestations.

• Vinegar Solution: A mixture of white vinegar and salt can be sprayed onto weeds to dry them out. Be cautious when using vinegar, as it can also harm surrounding plants.

• Baking Soda: Sprinkling baking soda into cracks can make the environment inhospitable for weed growth.

• Flame Weeding: A propane torch can be used to burn weeds down to the root, preventing regrowth.

Permanent Solution: Sealing the Expansion Joints and Cracks

The most effective way to stop weeds from growing in concrete cracks is to seal them completely. By blocking the gaps with a backer rod and sealant, you remove the space where weeds can take root.

Step-by-Step Guide to Sealing Concrete Cracks

1. Measure the Gap: Determine the width of the expansion joint or crack. A carpenter’s pencil, which is typically 1/2 inch by 1/4 inch, can be a useful reference tool.

2. Select the Right Backer Rod: Choose a backer rod slightly larger than the measured gap (you can use a pool noodle for this- simply cut to the desired width). For example, if the crack is 1/2 inch wide, use a 5/8 inch or 3/4 inch backer rod. The goal is to create a snug fit so that the sealant does not seep underneath.

3. Insert the Backer Rod: Press the backer rod firmly into the gap, ensuring that it sits about 1/4 inch below the surface of the concrete. This prevents excessive sealant usage and ensures a durable bond.

4. Choose the Right Sealant:

   • For level surfaces, use a self-leveling sealant such as Sika Self-Leveling Sealant.

   • For slightly sloped surfaces, use a semi-self-leveling sealant like Tremco Vulkem 45 SSL to prevent pooling and uneven curing.

5. Apply the Sealant: Fill the expansion joint with the sealant, ensuring complete coverage of the crack.

6. Blend the Sealant with Sand: Immediately after applying the sealant, lightly sprinkle sand on top. This helps the sealant blend naturally with the concrete surface and prevents debris from sticking while it cures.

7. Allow Proper Curing: Depending on the product used, the sealant may take 24-48 hours to fully cure. Avoid walking or driving over it during this time.

Important Tips and Considerations for Best Results

• Proper Preparation is Key: If the backer rod is not securely placed, it can float to the top of the sealant, causing issues with adhesion and durability.

• Check Weather Conditions: Avoid sealing cracks on extremely hot days (above 80°F) or in direct sunlight, as this can cause bubbling or improper curing.

• Use an Alternative Backer Rod: For larger or irregular cracks, a pool noodle can be custom-cut to serve as a backer rod.

• Regular Maintenance: Even after sealing, periodically check for any wear and tear to ensure long-lasting results.

Say Goodbye to Weeds for Good

Weeds growing in concrete cracks can be a persistent problem, but with the right approach, you can eliminate them for good. While temporary solutions like Preen granules offer a quick fix, sealing the cracks permanently is the best way to prevent weeds from returning. By following these simple DIY methods, you can keep your driveway and sidewalks looking clean and well-maintained all year round.

Whether you choose to apply a short-term solution or invest in a long-term fix, taking action today will save you time and frustration in the future.