Laying paving stones requires careful attention to the base, and one of the most common questions for DIYers and professionals alike is what to put under paving stones. While it might seem like a simple matter of just digging a hole and placing the stones, the materials beneath the surface are critical for long-term stability, drainage, and preventing sinking or shifting. The correct base is the invisible foundation that supports the entire paved area, distributing weight and resisting the forces of erosion and ground movement.
At its core, the primary function of what goes under paving stones is to create a stable, level, and well-drained platform. A proper base prevents the pavers from absorbing water, which weakens the sand and stone underneath. It also provides a rigid layer that stops the ground below from compacting unevenly over time. Without this essential layer, you risk cracks, trip hazards, and the entire surface needing to be redone, making the initial effort in selecting the right materials a worthwhile investment.
Understanding the Base Layers
The structure beneath a paved area is typically composed of multiple layers, each serving a specific purpose. You generally start with the subgrade, which is the native soil. This layer is often compacted and sometimes treated. On top of this, you add a base course, and finally, a bedding layer. Understanding the role of each layer is key to knowing exactly what to put under paving stones and in what order.
The Subgrade and Its Preparation
The subgrade is the existing soil beneath your project. Its condition is vital; if it's soft, muddy, or prone to shifting, no amount of top-layer material will fix the problem. Proper preparation often involves removing organic matter, excavating to a sufficient depth, and compacting the soil to create a solid, firmer foundation. This step ensures that the base materials are not sinking into the ground below.
The Primary Base Course: Crushed Stone
For most durable paving projects, the material directly on the compacted subgrade is crushed stone, often referred to as aggregate base or road base. Materials like crushed granite, limestone, or recycled concrete are ideal because they have jagged edges that lock together tightly. This angular shape creates a very stable and compactable layer that provides excellent drainage and prevents water from pooling underneath the final paving stones.
Bedding Sand: The Final Comfortable Layer
On top of the compacted crushed stone base sits a thin layer of coarse sand. This bedding layer is what allows you to level the individual paving stones perfectly. Unlike regular builder's sand, which can shift and compact, this is typically sharp, angular sand that locks together. It acts as the cushion that ensures the pavers sit evenly and provides slight adjustment during installation. Using the correct type of sand here is part of what to put under paving stones that ensures the surface remains flat and stable.
Material Comparison and Best Practices
Choosing the right materials involves understanding the specific properties and benefits of each option. Below is a comparison of common base materials to help clarify what works best and why.
| Material | Common Use | Key Benefit |
|---|---|---|
| Crushed Stone (e.g., 3/4" Gravel) | Primary base layer | Provides superior drainage and load-bearing strength |
| Coarse Bedding Sand | Setting bed for pavers | Allows for fine leveling and interlock |
| Geotextile Fabric | Between subgrade and stone | Separates soil from stone and prevents weed growth |
| Edge Restraints | Perimeter of the paved area | Prevents lateral movement of the stone base |
Common Mistakes to Avoid
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One of the biggest errors is skipping the geotextile fabric. This permeable fabric is placed between the compacted subgrade and the crushed stone. It prevents the soil from mixing into the stone base, which would ruin the drainage and stability. Another frequent error is using polymeric sand or fine dust sand as the base material; these materials do not compact well and will not provide the necessary support, leading to sinking pavers over time.
The final layer touching the paving stones is also critical. While polymeric sand is excellent for filling the joints to lock the surface together, the base must remain crushed stone and sand. Ensuring you have the correct what to put under paving stones setup—from aggregate base to bedding sand—creates a durable system that handles weather, weight, and time without failing.