Crushed Stone Prevents Weeds Paving Blocks

The installation of paving blocks can incorporate bricks and crushed stone as a foundation. This helps inhibit the growth of weeds between the paving units. 

In the photo above, the red brick foundation serves to stabilize the paving blocks (connecting blocks), minimizing movement. This paved area is intended solely for pedestrian use, not for vehicular traffic. 

A thin layer of a cement-sand mixture is applied over the soil to lock the red bricks and crushed stone in place. This prevents the crushed stone from sinking into the soil over time due to water exposure, while also creating a more robust foundation capable of supporting loads—ensuring the paving does not easily subside or shift. The cement-sand layer is only about 1 centimeter thick; its purpose is merely to secure the crushed stone, not to create a solid, impermeable seal over the ground. 

As shown also in the photo, a long piece of wood is used to level the crushed stone spread over the cement-sand layer, ensuring it aligns with the height of the red bricks. If leveling the crushed stone proves difficult, more red bricks can be added. Because of their uniform shape, red bricks are easier to level. Whereas the irregular shape of crushed stone makes it more challenging to achieve an even surface. 

Crushed stone allows rainwater to drain from the surface of the paving, passing through the gaps and into the soil, which prevents water from pooling on the pavement. While using a larger amount of cement would result in a stronger, more load-bearing foundation, it could also hinder water from seeping into the ground. 

Conversely, using a foundation with a high sand content creates an environment conducive to the growth of moss, weeds, grasses, and other small plants, which can spread through the sand, navigate the gaps between the paving blocks, and emerge on the surface. Plant roots can easily spread through sand, but they struggle to grow in the wide spaces between pieces of crushed stone.  

Because sand grains can form capillary voids capable of retaining water, which makes them favorable for plant roots. 

Plant roots easily attach or hold on between grains of sand. However, they have a harder time attaching themselves between crushed stones because the gaps are wider, and no water is trapped by capillary voids.

Sand is often used as a paving base, because it is relatively inexpensive, and easy to spread and level. 

Sand is also commonly used to fill the gaps between paving blocks to stabilize them. The sand in the gaps absorbs water through capillary action, providing a favorable environment for moss, grass, and other plants to grow.

In the photo above, some of the paving blocks have already been installed. If any part of the paved surface sits too high, it can be adjusted by tapping down the protruding pieces of crushed stone. A small amount of cement may be added to fill in areas that are too low. Avoid using excessive sand to level the surface, as plant roots—particularly from creeping plants—can grow into it. 

A drawback of using crushed stone as a base for paving is that the blocks may still shift when stepped on. Use a small amount of cement to secure any blocks that move excessively. If the paving blocks are uniform in size and installed tightly and neatly, such movement can be minimized. 

Some suggest that mixing sand with limestone to create a base for paving can help prevent weeds from growing between the blocks. However, lime is relatively expensive, and its presence can also kill plants intentionally grown around the paved area.