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When planning a patio, choosing the right gravel is key to ensuring proper drainage and avoiding costly water damage. Maryland’s heavy rainfall and clay soils make this even more important. Here’s a breakdown of five gravel types and their best uses:
- Pea Gravel: Small, smooth stones that don’t compact, making it great for water flow. Ideal for drainage layers beneath patios.
- Washed #57 Gravel: Angular stones that interlock for stability while maintaining good drainage. Perfect for paver bases.
- CR-6 Gravel: A mix of fine dust and larger stones. Compacts tightly, offering a stable base, but less effective for drainage.
- River Rock: Smooth, rounded stones that allow water to flow but lack compaction. Best for decorative drainage around patio edges.
- Decomposed Granite: Fine, angular particles that compact well. Works for rustic patios and as a permeable paver base.
Quick Comparison
| Gravel Type | Drainage Performance | Compaction Ability | Best Use Cases | Cost Range (per ton) |
|---|---|---|---|---|
| Pea Gravel | Excellent | Poor | Drainage layers, light foot traffic | $30–45 |
| Washed #57 | Excellent | Good | Paver bases, heavy-duty applications | $25–40 |
| CR-6 | Moderate | Excellent | Base layers, high-traffic patios | $20–35 |
| River Rock | Good | Poor | Decorative accents, patio edges | $40–65 |
| Decomposed Granite | Moderate | Excellent | Rustic patios, walkways | $35–50 |
For a stable and well-draining patio, combine a compactable base like CR-6 or decomposed granite with a porous top layer such as pea gravel or washed #57. This ensures durability and proper water management.
1. Pea Gravel
Particle Size and Shape
When it comes to effective drainage, the type of gravel you choose makes a big difference. Pea gravel consists of small, smooth, and rounded stones, roughly the size of peas[1]. Thanks to their rounded shape, these stones don’t lock together, creating plenty of open spaces for water to flow through. This natural structure is key to ensuring excellent water movement.
Drainage Performance and Compaction
Pea gravel’s loose composition is what makes it stand out for drainage. Water can easily pass through, and because the stones are rounded, they resist compacting over time. This means the gravel stays porous, maintaining clear pathways for water even after extended use. For patios, where proper water management is crucial, this is a major advantage.
Best Use Cases
Pea gravel works perfectly as a drainage layer beneath patios. Its open, non-compacting structure keeps water flowing efficiently, helping to prevent pooling or water damage.
2. Washed #57 Gravel
Particle Size and Shape
Washed #57 gravel consists of angular stones ranging from ¾ to 1 inch in size. Unlike the smooth, rounded look of pea gravel, these stones have sharp, jagged edges. This angular shape allows the stones to interlock while still leaving spaces for water to pass through. The "washed" label means the gravel has been thoroughly cleaned to remove dust, fine particles, and debris that could block drainage. This unique shape and cleaning process make it a great choice for projects requiring both stability and drainage.
Drainage Performance
This gravel strikes a balance between water flow and structural support. Thanks to the washing process, fine particles that could obstruct water movement are removed, ensuring effective drainage. While water flows through it more slowly than through pea gravel, it’s still highly efficient. This makes it a solid choice for situations where you need good drainage combined with some level of structural compaction.
Compaction Ability
The jagged edges of washed #57 gravel give it an edge – literally – when it comes to compaction. As the stones press together, their angular surfaces lock into place, forming a stable and supportive base. This compaction doesn’t compromise porosity, so water can still flow through effectively, even after the gravel is compressed.
Best Use Cases
Washed #57 gravel is a go-to material for patio installations. It works particularly well as a base layer for patio pavers or flagstones, offering the perfect combination of drainage and stability. Its ability to compact without losing permeability makes it ideal for creating a foundation that resists shifting over time. This is especially beneficial in areas with clay soil or regions prone to freeze-thaw cycles, where a reliable and stable base is essential for long-term durability.
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3. CR-6 Gravel (Crusher Run)
CR-6 gravel, often called crusher run, offers a unique mix of stone sizes that make it a go-to choice for sturdy base layers.
Particle Size and Shape
CR-6 gravel is a blend of particles ranging from fine dust to stones as large as 1.5 inches. This mix creates what contractors refer to as a "well-graded" material. Essentially, the variety of sizes allows the stones to fit together tightly, forming a dense and stable foundation. The angular and jagged shape of the stones, a result of crushing larger rocks, enhances this interlocking ability. Unlike washed gravel, CR-6 retains the fine dust and stone particles from the crushing process, giving it a dusty texture and a grayish hue.
Drainage Performance
When it comes to drainage, CR-6 gravel is not the most efficient option. The fine particles and dust fill the gaps between larger stones, creating a compact surface that tends to shed water rather than allow it to seep through. This can lead to water pooling or runoff if the material isn’t used properly in areas like patios or walkways.
Compaction Ability
One of CR-6’s standout features is its ability to compact tightly. The mix of stone sizes and fine particles locks together when compacted with tools like a plate compactor or roller. The fine dust acts like a binder, filling in voids and forming a surface that’s almost as solid as concrete when moistened and compacted correctly. This makes it an excellent choice for creating a stable base layer that resists settling or movement over time.
Best Use Cases
CR-6 gravel shines as a foundational layer beneath more porous materials. It’s particularly effective for heavy-duty applications like paver patios, walkways, and driveways. By using CR-6 as the base layer, you can ensure a stable surface that prevents shifting while directing water runoff to designated drainage areas instead of allowing it to seep into the ground directly.
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4. River Rock
River rock offers a polished, natural look, making it a popular choice for drainage projects. However, its smooth texture can present challenges when structural stability is needed.
Particle Size and Shape
River rock typically ranges from 0.5 to 3 inches in diameter, with stones between 1 and 2 inches being ideal for drainage purposes. These rocks are shaped by water erosion, giving them smooth, rounded surfaces that not only enhance water flow but also provide a visually appealing finish. The natural tumbling process removes sharp edges, resulting in oval or circular shapes. River rock comes in a variety of colors, depending on its source – neutral grays and browns are common, but you can also find more vibrant reds, blues, and mixed tones. These aesthetic and functional features make river rock a standout choice for drainage near patios and other visible areas.
Drainage Performance
The rounded edges of river rock are excellent for promoting water flow. Unlike angular stones that interlock tightly, river rocks create open gaps, allowing water to pass through easily. Additionally, their uniform sizing reduces the presence of fine particles that might clog drainage systems. This makes river rock particularly effective for applications like French drains, drainage swales, and areas around patio edges, where quick water movement is essential.
Compaction Ability
One downside of river rock is its poor compaction ability. The smooth surfaces prevent the stones from locking together, causing them to shift or roll under pressure. This lack of friction makes river rock unsuitable as a base material for patios or walkways, where stability is crucial. However, this same quality is what makes it ideal for drainage, as the loose arrangement allows water to flow freely through the stones.
Best Use Cases
River rock shines in decorative drainage projects where both functionality and appearance are important. It works particularly well as a top layer in French drains, eliminating the need to conceal drainage systems thanks to its attractive look. Around patio edges, river rock creates visually appealing borders that efficiently channel water away from hardscaped areas. It’s also a great choice for dry creek beds designed to manage stormwater runoff, as its natural appearance mimics real stream beds. For patio use, river rock is best suited as a decorative layer, filling gaps between pavers or serving as a transition between hardscaping and landscaping.
5. Decomposed Granite
Decomposed granite (DG) is a naturally occurring material formed as granite weathers and breaks down into fine, angular particles. It retains its natural mineral content, making it a popular choice for patio surfaces, especially where drainage is a concern. However, DG behaves quite differently from standard gravel, so understanding its properties is key.
Particle Size and Shape
DG consists of a mix of particle sizes, ranging from fine, sand-like grains (less than 1/8 inch) to small pebbles about 3/8 inch in diameter. Most of the particles fall between 1/16 and 1/4 inch, creating a blend of granite sand, tiny rock fragments, and clay-like fines. Unlike manufactured gravel, DG has a natural gradation of particle sizes, resulting from the weathering of minerals like feldspar, quartz, and mica. This process not only gives DG its angular shapes but also its range of colors, which can vary from tan and gold to reddish-brown and gray, depending on the mineral composition of the original granite. These characteristics make DG an integral part of multi-layered drainage systems.
Drainage Performance
The drainage ability of DG depends heavily on the amount of fine particles in the mix. Standard DG typically contains about 10–15% clay and silt-sized particles, which can slow down water infiltration compared to cleaner gravels. When compacted, these fines fill the gaps between larger particles, encouraging runoff rather than quick absorption. Stabilized DG, which includes polymer binders, improves water resistance and reduces erosion during heavy rains, making it a better option for areas exposed to frequent or intense rainfall.
Compaction Ability
One of the standout features of decomposed granite is its ability to compact effectively. Thanks to the variety of particle sizes, the angular fragments interlock tightly, while the finer particles act as a natural binder, filling in the gaps. When installed correctly, DG forms a dense, firm surface that can handle foot traffic and even light vehicles. This makes it a versatile choice for outdoor spaces, providing a stable and cohesive layer for various applications.
Best Use Cases
Decomposed granite works particularly well for rustic patios that require a sturdy, well-draining surface. It’s also an excellent permeable base for pavers or flagstones, offering both stability and gradual water infiltration. For homeowners who want a low-maintenance surface with the appearance of natural stone, stabilized DG is a practical option for areas with moderate foot traffic. Its natural look and functional properties make it a go-to choice for patios and transitional borders.
If you’re thinking about using decomposed granite for your patio project, reaching out to the professionals at Pro Landscapes MD can help ensure proper installation and lasting results.
Gravel Type Comparison Chart
When selecting gravel for your patio or project, it’s essential to consider factors like particle size, drainage, compaction, use, and cost. The chart below outlines key gravel options, making it easier to find the best fit for your needs.
| Gravel Type | Particle Size | Drainage Performance | Compaction Ability | Best Use Cases | Cost Range |
|---|---|---|---|---|---|
| Pea Gravel | 1/8" to 3/8", round, smooth stones | Excellent – gaps between stones allow rapid water flow | Poor – smooth stones don’t interlock well | Decorative surfaces, French drains, areas with light foot traffic | $30–45 per ton |
| Washed #57 Gravel | 1/2" to 1", angular crushed stone | Excellent – clean stone with minimal fines promotes fast drainage | Good – angular shapes provide moderate interlocking | Drainage layers, pipe bedding, heavy-duty applications | $25–40 per ton |
| CR-6 Gravel | 3/4" down to fine dust blend | Moderate – fines can slow drainage but still permeable | Excellent – wide range of sizes creates maximum density | Base layers, driveways, high-traffic patios | $20–35 per ton |
| River Rock | 1" to 3", smooth, rounded stones | Good – larger gaps allow water flow but slower than smaller gravel | Poor – smooth surfaces don’t compact or interlock | Decorative accents, low-traffic areas, landscape features | $40–65 per ton |
| Decomposed Granite | 1/16" to 3/8", angular particles with 10–15% fines | Moderate – fines reduce infiltration compared to clean gravel | Excellent – angular particles and natural binders create a firm surface | Rustic patios, paver base, walkways, natural-looking surfaces | $35–50 per ton |
Key Takeaways
- Drainage: Pea gravel and washed #57 gravel excel in water flow due to their minimal fines, while river rock offers decent drainage but lacks structural contact.
- Compaction: For stability, CR-6 and decomposed granite are top choices. Their mix of particle sizes and angular shapes ensure a tightly packed, firm base.
- Cost Considerations: Prices vary by region, but CR-6 provides excellent value for structural applications, especially in the Mid-Atlantic area.
For the best results, use a compactable base like CR-6 or decomposed granite to create a solid foundation. Then, add a porous top layer such as pea gravel or washed #57 to balance stability and drainage. This combination ensures both durability and functionality for your project.
Conclusion
Choosing the right type of gravel for your patio drainage project can mean the difference between a well-functioning outdoor space and costly repairs down the line. The comparison chart provided can help simplify your decision. Different gravel types serve distinct purposes – pea gravel works well for drainage in French drains, while CR-6 provides excellent compaction for stable base layers.
The key to success lies in aligning the materials with your specific project needs. Think about factors like foot traffic, soil conditions in your area, and long-term maintenance requirements when making your choice. In Maryland’s climate, proper drainage is essential to avoid expensive damage. Understanding these elements helps you select both the right materials and the best installation methods.
Expert installation plays a crucial role in ensuring effective drainage. Local professionals can offer solutions tailored to your specific needs. Pro Landscapes MD, for instance, has extensive experience with drainage systems, including French drains, stormwater management, and grading services, all designed with central Maryland’s unique conditions in mind.
Their approach combines the right gravel selection with skilled installation techniques, addressing everything from drain pipe placement to land leveling. By understanding local soil conditions and common drainage challenges, they help homeowners avoid issues like standing water, foundation damage, and landscape erosion.
FAQs
What should I consider when selecting gravel for patio drainage in Maryland’s rainy climate?
When choosing gravel for patio drainage in Maryland’s rainy climate, it’s important to consider size, shape, and permeability. For example, pea gravel, made up of small, rounded stones, is a great option. Its design allows water to pass through easily while resisting compaction, which helps prevent puddles and promotes efficient drainage.
You’ll also want to pick gravel that stays loose even during heavy downpours. Using the right drainage materials is key to managing Maryland’s frequent storms and safeguarding your patio from flooding or water damage.
Why is using a compactable base with a porous top layer important for patio drainage and stability?
Using a solid base paired with a water-permeable top layer is key to keeping your patio both functional and long-lasting. A stable foundation, often made from materials like open-graded gravel, provides the strength needed to prevent shifting or settling over time. Meanwhile, the porous top layer allows water to drain through efficiently, helping to avoid puddles, reduce moisture accumulation, and limit erosion. This combination ensures your patio can handle heavy rains while staying sturdy and reliable.
Why is pea gravel often preferred for drainage layers over materials like CR-6 or decomposed granite?
Pea gravel is a favorite for drainage layers thanks to its small, rounded stones that naturally create gaps, making it easy for water to pass through. Unlike materials like CR-6 or decomposed granite, which can pack down tightly and restrict water flow, pea gravel stays loose, helping to avoid water buildup.
This quality makes it perfect for areas where drainage is a priority, such as patios, walkways, or garden beds. Plus, its smooth texture not only makes it simple to handle but also adds a visually appealing touch to landscaping projects.
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