In this article, we’ll explore key questions surrounding the construction and maintenance of patio bases, providing insights into the necessity of base layers, optimal thicknesses, and the use of various materials. Whether you’re planning a new patio, a walkway, or any hardscaping project, our concise yet thorough guide, complete with detailed tables and guidelines, will equip you with the knowledge to build a durable and stable foundation for your outdoor spaces.
Do Patios Need a Base Layer?
Patios will require a base layer if vehicles are driving on top of the however, base layers are optional for foot traffic only.
Base needs depend on the surfacing type. Interlocking concrete pavers require a base while materials like stamped concrete may perform fine without, but could benefit from one. See Table 1.
Remember that bases spread loads and provide critical support. Omit only with good reason.
Compacting base gravel with plate compactor
Table 1: Base Guidelines by Surface Type
| Surface Material | Base? | Depth | Notes |
|---|---|---|---|
| Paving Stones | Always | 4-6 inches | Essential in most cases |
| Concrete Pavers | Usually | 4-9 inches | Also helps level |
| Asphalt | Often | 3-5 inches | Depends on traffic load |
| Gravel | Sometimes | 4-8 inches | Depth varies with usage |
| Brick | Generally | 2-4 inches | Best with a sturdy base |
| Natural Stone | Varies | 3-6 inches | Dependent on stone type |
| Rubber Tiles | Rarely | 2-3 inches | Mostly for play areas |
| Wood Chips | No | 2-4 inches | Commonly used in gardens |
| Sand | No | 2-3 inches | Good for drainage |
| Composite Decking | Usually | 3-5 inches | Requires solid support |
General Patio Sub base Cross Section Shown Below
What Thickness Should a Patio Sub Base Be?
For patios, a 4-6 inch base of packed gravel is typical. Driveways often use 6 inches minimum depth. Commercial projects may exceed 9 inches base thickness.
There’s a general rule to make base layers at least twice the maximum rock size to prevent pressure points.
So if the largest rocks are 1 inch, the minimum depth should be 2 inches. See diagram:
Thus, for 1.5 inch road base stone, the formula gives 1.5 x 2 = 3 inch minimum. Round up to the nearest inch.
If the existing base will be 4 inches, the maximum rock size should be 4 / 2 = 2 inches.
Table 2: Recommended Base Depth
| Type of Paving | Sub-base Required? | Thickness (mm) | Remarks |
|---|---|---|---|
| Flexible Block Paving | Always | 75-150 | Minimum 75mm for pedestrian areas, 100-150mm for driveways, over 150mm for commercial use |
| Rigid Block Paving | Typically | 100-225 | Can be positioned under the base layer |
| Patio Flags | Sometimes | 75-100 | Optional, but beneficial for elevating levels |
| Indian Sandstones | Sometimes | 75-100 | Optional, but advantageous for raising levels |
| Yorkstone Flags | Sometimes | 75-150 | Not required for pedestrian areas, suggested for driveways |
| BS Flags | Generally | 75-150 | Unnecessary for patios, advised for driveways, commonly specified for commercial projects |
| Gravel | Generally | 75-150 | Skippable in ornamental areas, essential for trafficked zones |
| Setts/Cubes | Generally | 75-150 | Optional for rigid construction, crucial for flexible construction |
| Cobbles | Sometimes | 75-150 | Potential use under base layer |
| Tarmac | Always | 100-150 | 100mm for footpaths and light driveways |
| Concrete - PIC | Typically | 100-150 | Frequently excluded beneath PIC on driveways, though this may not be ideal |
| Resin Systems | Typically | 75-150 | Varies based on the underlying surface type |
Can I Use Salvaged Materials as Base?
Base layers provide critical support, so durability matters. Scrimping with low-grade fill risks problems.
The issue with repurposed masonry and concrete is random sizes/shapes and gaps. The same for “hardcore” rubble.
Over time, backfill trickles into voids, allowing settling. Jagged pieces telegraph through, causing instability.
Avoid using whole bricks. Halved is better, but crushed masonry blended with clean gravel makes the best DIY base option. Topping this stabilized layer with 4-6 inches of road base stone completes a durable patio foundation able to withstand seasonal movement.
Cutting corners on base build shortchanges overall longevity. Proper base materials make sound, long-term investments.
What Base is Ideal for Sandstone Pavers?
The optimal base for sandstone pavers is crushed stone or limestone, known for its compaction and high-traffic endurance. Sand is also favoured for its drainage capabilities.
Which Sub-Base Material is Best for Paving Slabs?
MOT Type 1, comprising crushed limestone, concrete, or granite without fines, is the preferred sub-base for paving slabs due to its superior quality and stability.
What Sub-Base is Needed for a Porcelain Patio?
For a porcelain patio, a Type 1 MOT or General Sub-Base (GSB) aggregate is essential for providing strength and stability. It should be raked out to create an even layer, approximately 30mm below the string line.
What Should be Placed Under Porcelain Pavers?
According to Best Practices for Porcelain Pavers a sand base is suitable for small patios or walkways over concrete or level ground, especially in dryer climates. This involves installing porcelain pavers over a compacted sand base.
