Moss growing between pavers is a common issue that affects the appearance and safety of walkways and patios. While the soft, green growth may seem harmless, it creates dangerously slippery surfaces, particularly when wet. Finding a durable solution requires addressing both the existing growth and the underlying environmental factors that allow it to thrive. This comprehensive approach ensures the problem is prevented from returning.
Understanding the Conditions that Encourage Moss Growth
Moss is a non-vascular plant that absorbs moisture and nutrients directly from the air and surface. The primary factors creating an ideal habitat are consistent moisture and a lack of direct sunlight. Shaded areas, such as those beneath trees or on the north side of a structure, stay wet for extended periods after rain, allowing moss spores to settle and germinate.
Poor drainage also contributes significantly, as standing water or slow-drying surfaces keep the paver joints saturated. Over time, airborne dust, dirt, and organic debris accumulate within the joint sand, creating a nutrient-rich soil layer. This debris traps moisture, offering the moss a stable medium to anchor and develop into dense mats. Addressing these conditions is foundational to long-term moss control.
Immediate Physical Removal Methods
The most direct way to eliminate existing moss is through mechanical action, which involves physically scraping the growth out of the paver joints. Simple scraping tools or a sturdy utility knife can be used to pry the visible moss structure out of the crevices. For surface growth, a stiff-bristled brush or a wire brush is effective for scrubbing moss patches off the paver faces and the top layer of the joints.
Pressure washing is an alternative method that uses high-velocity water to blast the moss away quickly. This method requires caution, as excessive pressure can damage the paver surface or wash out too much of the joint sand. Removing the joint sand destabilizes the pavers and creates an easier location for new moss and weeds to root. When using a pressure washer, employ a wide fan tip and moderate pressure to minimize the loss of joint material.
Chemical and Natural Killing Treatments
Once the bulk of the moss is physically removed, a killing agent can be applied to destroy any remaining spores and roots within the joint material. Commercial moss-killing products often contain zinc sulfate or ferrous sulfate, which are effective at desiccating and killing the plant structure. These products are typically applied as a spray or powder and allowed to sit for several hours before being rinsed away, following the manufacturer’s instructions.
A common household alternative is a diluted bleach solution (one part bleach mixed with three parts water) applied to the affected joints. Because this chemical treatment is potent, surrounding vegetation should be pre-wet with plain water to minimize accidental damage from runoff. Alternatively, a natural solution can be made using household white vinegar, which contains acetic acid that creates an inhospitable environment for moss.
For tough growth, a five percent concentration of white vinegar can be sprayed directly onto the moss and left for about an hour to break down the plant tissue. Baking soda (sodium bicarbonate) is another option that kills moss by increasing the surface alkalinity. A liberal sprinkling of baking soda can be left on the wet moss for 24 hours before being swept away.
Long-Term Prevention Strategies
The most effective way to keep moss from growing is by changing the environment to make it unlivable for the plant. One structural approach involves stabilizing the paver joints by sweeping in polymeric sand. Unlike regular sand, polymeric sand contains polymers that harden when activated with water, creating a tight, mortar-like seal between the pavers. This hardened barrier locks the pavers in place, resists washing out, and prevents organic debris from accumulating in the joints, thus eliminating the moss’s growth medium.
Applying a paver sealer after cleaning and sanding is another layer of defense that reduces porosity and moisture absorption. Sealers create a water-repellent surface that makes the paver faces and joints dry out faster, deterring moss and algae growth. Many sealers include antifungal additives that suppress biological contaminants, and a sealed surface is easier to clean during routine maintenance.
Environmental modification is a simple, effective strategy to prevent moss return. Moss requires shade and persistent dampness, so increasing sunlight exposure and improving air circulation is beneficial. Trimming overhanging tree branches or shrubs allows more sun to reach the surface, helping the pavers to dry more rapidly after rain or irrigation. Additionally, ensuring the paver surface has a slight slope and that nearby gutters or downspouts are not directing water onto the area will prevent pooling and improve drainage.