Gap 20 aggregates are ideal for Auckland’s rainy climate because they offer excellent drainage, strong compaction, and long-term stability—even in persistently wet conditions. Whether you're building driveways, paths, or retaining walls, Gap 20 creates a durable base that resists erosion and pooling in soggy soil.
Introduction: Rain, Rain, and More Rain — Welcome to Auckland Landscaping
If you’ve ever tried to tackle an outdoor project in Auckland, you know the weather can be… unpredictable. One minute it's blue skies, the next, a relentless downpour. While this lush climate is great for gardens, it creates a serious challenge for anyone laying paths, driveways, or structural foundations. Too much water can turn a picture-perfect landscape into a mud pit.
That’s where Gap 20 aggregates come in.
In this article, we’ll explore why Gap 20 is not just suitable but exceptional for Auckland’s rainy environment. We'll look at its unique properties, how it compares to other aggregates like Gap 40 and Gap 7, and where it shines in real-life landscaping projects.
What Exactly Is Gap 20 Aggregate?
To put it simply, Gap 20 is a type of graded gravel made up of crushed stones and fine particles, with the largest stone size being around 20mm. The "GAP" stands for "General All Passing," meaning the mix contains a range of sizes from dust to 20mm, allowing the material to compact tightly and create a strong, stable surface.
This compactability, combined with its drainage characteristics, makes Gap 20 a go-to option for foundations and sub-bases—especially in environments where water is a frequent visitor.
Auckland’s Rainfall: A Constant Test for Landscape Materials
Auckland sees an average of 1,200–1,400 mm of rain per year, with rainfall spread fairly evenly across the months. While that might not sound extreme, it's the frequency and unpredictability of showers that cause the most damage to outdoor surfaces and structures.
Poorly drained soil becomes waterlogged. Weakened foundations shift. Mud creeps into all the wrong places.
In such conditions, the choice of base material becomes not just important—but critical. That’s where Gap 20’s specific strengths show up in force.
Why Gap 20 Aggregates Perform So Well in Wet Conditions
1. Superior Drainage Without Erosion
Despite its compactable nature, Gap 20 still allows water to pass through, reducing surface water buildup. Unlike clay-heavy fills or overly fine soils that trap water, Gap 20’s granular structure lets rainwater drain gradually while keeping the surface stable.
This makes it ideal for:
- Driveways that slope toward stormwater channels
- Paths through garden areas prone to runoff
- Base layers beneath permeable pavers or gobi blocks
You get both firmness and breathability—a balance few materials strike well.
2. Tight Compaction = Lasting Stability
Gap 20 compacts tightly when laid and compacted correctly, which prevents movement during heavy rains. This makes it less likely to rut, settle unevenly, or erode—problems often seen with loose stones or poorly graded fill.
It’s not just for professionals either. With a bit of effort and a hired compactor, even DIYers can achieve a solid finish with Gap 20.
3. Reduced Maintenance in Wet Zones
Once laid and compacted, a Gap 20 base resists weed growth, puddling, and surface breakdown. In contrast, looser materials may need refilling or reshaping after just a season of heavy rain.
This long-term reliability means fewer repairs, less mess, and peace of mind—especially in high-foot-traffic zones or sloped driveways.
Comparing Gap 20 with Other Aggregates
Choosing the right aggregate depends on your project’s needs. Let’s look at how Gap 20 compares to a few popular options in Auckland.
▸ Gap 40: Better for Deep Base, Not Ideal for Surface Layers
Gap 40 contains larger stones (up to 40mm), making it excellent for deep foundational work under roads or heavy commercial areas. However, it’s often overkill for residential paths or small retaining walls, where Gap 20 provides enough strength with smoother finish potential.
▸ Gap 7: Good for Finishing, Not for Foundations
Gap 7 is finer and often used as a top layer over Gap 20. It doesn’t offer the same foundational strength but helps achieve a clean, compact finish. In wet areas, a layered system—Gap 40 base, Gap 20 sub-base, Gap 7 top—is ideal for ultimate stability.
▸ Decorative Mulch: Attractive But Not Functional for Base Work
While decorative mulch is perfect for aesthetic garden beds and moisture retention, it’s not meant for foundational or structural use. It shifts easily in rain and does nothing to stabilize heavy loads or foot traffic areas.
Real-World Examples: Gap 20 in Action
✅ North Shore Garden Path That Stays Put
A landscaping company in Takapuna replaced an old gravel path prone to washouts with a properly compacted Gap 20 base. After one of the wettest winters on record, the path remained firm, with no signs of erosion. The client’s only comment? “Why didn’t we do this sooner?”
✅ Driveway Upgrade in Waitākere Ranges
A steep driveway was consistently turning to mud each winter. After excavation and layering 150mm of Gap 20, followed by compacting and laying gobi blocks, the problem was solved. The surface handled both car weight and flood-prone storms without so much as a rut.
✅ Raised Garden Beds with Integrated Drainage
Even raised planters can suffer from poor drainage in Auckland. Some savvy landscapers now use Gap 20 as a base layer inside raised beds before adding soil, ensuring water doesn’t pool around plant roots.
Expert Tips for Using Gap 20 in Rainy Climates
- Compact in Dry Weather: Even though it handles moisture well, Gap 20 compacts best when laid in dry conditions. Avoid installing during or just after heavy rain for optimal results.
- Use Geotextile Fabric Underneath: This prevents mixing with subsoil and further improves drainage in very wet zones.
- Don’t Skip the Edging: Properly contained aggregates last longer. Use timber, stone, or metal edging to keep everything in place.
- Add a Crown on Paths or Driveways: Slightly raising the center ensures water flows off rather than pooling.
FAQs
Q: Can I use Gap 20 on its own for a driveway in Auckland?
Yes, for light to moderate use. For heavier vehicles or steep slopes, consider adding a Gap 40 base first.
Q: How thick should I lay Gap 20 for walkways?
Typically, 75–100mm is sufficient for footpaths. For driveways, go for 150mm or more depending on soil conditions.
Q: Is Gap 20 safe for pets and kids?
Absolutely. Once compacted, the surface is firm and safe to walk or play on—just ensure proper edging to avoid loose stones.
Q: Will Gap 20 prevent weeds completely?
While no surface is 100% weed-proof, Gap 20 significantly reduces weed growth—especially when combined with weed matting.
Conclusion: A Smart, Rain-Ready Choice for Auckland Landscapes
In a city that sees more umbrellas than sunglasses, smart landscaping means planning for the rain—not just the sun. Gap 20 aggregates offer a practical, durable, and weather-resilient solution for all kinds of outdoor projects in Auckland.
Whether you're reinforcing a sloping driveway, laying a new path, or prepping for a retaining wall, Gap 20 gives you peace of mind that your project won't wash away with the next storm.
It’s the unsung hero under your feet—quietly keeping your landscape solid, rain or shine.
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