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Landscaping A Sloped Site: What You Need To Know

Landscaping A Sloped Site: What You Need To Know

Working with a sloped garden can be frustrating. As you battle soil erosion after heavy rain, struggle to push a lawnmower up an incline, or even just stare at the dead, unusable space, working with a gradient can feel like an expensive obstacle.
Before making any solid decisions about your landscaping plans, you need to understand the best way to work with a sloped site. In this guide, we’ll break down everything you need to know about creating your ideal space.

Assessing the Gradient

Before you start working, it’s important to understand exactly what you are working with.

Typically, the term ‘rise and run’ refers to the gradient of a slope compared to the horizontal distance. The most important consideration is that if a slope is too steep, water runoff can happen from erosion. Through careful planning, grading, and the right drainage solution, this can be dealt with.

A gentle slope has a 1:10 ratio. This is usually manageable with clever planting and minor surface levelling. A moderate slope is a 1:4 ratio. This typically requires structural intervention, such as small retaining walls, to prevent soil movement.

A sleep slope is a slope greater than 1:3, typically requiring heavy machinery for excavation and structural engineering to ensure the land is safe. This type of slope is considered more suitable for growing plants.

Considerations For When You’re Working On A Sloped Site

What’s Already There?

Before you begin digging and removing elements to start with a blank canvas, take a moment to consider what effect this will have on the site. If your site already has mature trees, removing them will disturb the soil, potentially causing movement and compromising the slope’s structural integrity. Of course, you can’t always preserve every tree on site, but it’s recommended that you remember the consequences of removing every tree.

Preserving Your View

A sloped site often benefits from a view. If you have this privilege, you can maintain this view in your landscaping plan. Consider the best way to enjoy this view, with platforms, decking or viewing points. However, keep in mind that planting further down will grow, and larger trees may obstruct your view in time.

Grading The Slope

Disturbing the slope compromises its structural integrity, and more support will be required. Grading the slope is the process of reshaping the land to ensure a solid base whilst also managing water runoff. Water will always take the path of least resistance, so if your slope is naturally running towards your home’s foundations, a heavy storm could lead to damp walls and damage to your property. Professional grading will slope the land away from structures to ensure that even in heavy downpours, water is directed correctly. The grading process will also include contouring to prevent soil erosion. Instead of a single steep run that erodes the topsoil, shallow channels will capture the water, slow it, and allow it to soak into the ground naturally.

Strength and Stability

Slopes are prone to mudslides in wet weather if not properly maintained. In heavy rainfall, the slope becomes saturated, causing the soil to slide. Planting trees is a good way to create a network of roots which binds the soil together and holds the slope in place.

Stop Rain From Eroding The Slope

When a slope has too much bare soil exposed, rain can dislodge and erode the soil over time. A good remedy is to plant shrubs and use rocks to cover the soil and slow water runoff.

Retaining Walls & Drainage

The biggest threat to a sloped landscape is not gravity; it’s water. Rainwater will soak into the slope, and the weight of the water creates hydrostatic pressure. Without the right drainage system, this pressure can push over a brick wall and create a lot of damage. A retaining wall holds soil in place and is typically used in sloping sites for safety when you’re cutting into a slope to create a terrace. It is necessary to have a retaining wall designed by a structural engineer to ensure it has structural strength to hold back the soil. Different materials can be used to create retaining walls, including timber sleepers, stone/brick walls, and concrete. Of course, the choice of materials used will depend on structural, drainage, and aesthetic considerations. A retaining wall is only as good as its foundation, so any wall over 1 metre will require a concrete footing and a calculated lean-back to resist the immense pressure of wet soil. Drainage is just as important to keep your garden in place. Using a variety of drainage options, including geotextile membranes, non-porous backfill, weepholes, and land drains, will help to properly deal with water and stop damage.

Logistics

Often overlooked is the sheer volume of soil that often needs to be moved when you’re working with a sloped garden. When you cut into a hillside to create a level terrace, the soil you remove will bulk up, creating a significant volume to then move. Sometimes, you will need specialist machinery to make the project a success, which is where a muck-away service is helpful. A professional will be able to ensure all waste is taken away and dealt with legally and efficiently, saving you the hidden costs and headaches of hiring skips and the labour involved.

A retaining wall holds soil in place and is typically used in sloping sites for safety when you’re cutting into a slope to create a terrace. It is necessary to have a retaining wall designed by a structural engineer to ensure it has structural strength to hold back the soil.

Different materials can be used to create retaining walls, including timber sleepers, stone/brick walls, and concrete. Of course, the choice of materials used will depend on structural, drainage, and aesthetic considerations.

A retaining wall is only as good as its foundation, so any wall over 1 metre will require a concrete footing and a calculated lean-back to resist the immense pressure of wet soil.

Drainage is just as important to keep your garden in place. Using a variety of drainage options, including geotextile membranes, non-porous backfill, weepholes, and land drains, will help to properly deal with water and stop damage.

Accessibility

Think about whether the design is accessible to everyone who wants to use it. This depends on the project, but consider adding steps alongside sloped paths, as well as railing and balustrades where necessary.

What Design Features Are Well Suited To A Sloped Site?

Terraces and Decking

The natural form of a sloped landscape is ideal for decking and terraces, as it maximises useful space and creates interest.

Seating and Furniture

A sloped space lends itself well to seating, and creating areas for socialising can be an excellent way to make a space more inviting.

Planting

Slopes can be dry when there has been little rain, but they can also become quite wet at the base after rain. Therefore, it’s important to choose the right plants that can tolerate the different water levels throughout the slope. A good mixture of ground cover, trees and shrubs is also a good way to avoid erosion.

Water Features

If you’d rather make use of the natural topography of the slope, water features are a good choice. Whilst flat garden spaces often need expensive artificial mounds and heavy pumps to create the movement of a water feature, a sloped site can create that movement for free. Following the natural grade of the land, you can create a cascading stream of pools, that fit in well with the landscape.

Beyond aesthetics, a water feature on a slope is a functional addition. It can also be a controlled drainage system. Instead of rainwater moving topsoil, water is better managed, collecting in a pond or soakaway at the bottom.

A sloped site isn’t a problem that needs to be solved. By finding the right solution for you, prioritising structural integrity and smart drainage, you can create a space you can enjoy whilst also adding value to your home.

Whether you need a full landscaping or site excavation, the Wilsons Groundworks team can help. Arrange a free site survey today.