Topographical Challenges: How To Increase Usable Space On A Cliff- or Hillside Property

Many of San Diego’s various neighborhoods have far larger lot sizes than is typical for a major metropolitan area. This is, in part, thanks to the highly varied topography of the city, with neighborhoods clustering about hillsides, ravines, and craggy coastal cliffs.

We’ve covered the challenges that we have encountered with the city’s unique topography many times in the past. One of the specialties a San Diego landscape company needs is to be well-versed in topography solutions for hillsides and cliffs to maximize usable space.

In order to overcome the spatial limitations of a steeply spaced property, the landscape architect and construction team must be able to design, construct, install, and connect features that allow for verticality, such as decking platforms and terracing. Even more importantly, these features need to be supported by complicated engineering techniques that preserve the integrity of the hillside and protect against erosion.

Vertical Features

A hillside property can’t be simply leveled to accommodate the owner’s need for space. Maximizing the usable space on a topographically challenging property requires a delicate mix of engineering and landscaping, creating a series of levels that can then be dedicated to a specific purpose.

This can be accomplished through decking, which uses a raised, level platform away from the ground, or terracing, which involves leveling a section of the slope. Each option has advantages and disadvantages that can be influenced by the properties of the land on which the property is situated.

Decking

If you’ve ever walked along California beaches, you’ve likely seen houses perched precariously on the steep sandstone cliffs that line the coasts. What little outdoor space is available is often limited to a diminutive decking area, supported by a series of thick timber stilts, which create a unique aesthetic for the property.

Decks are typically wooden platforms raised from the ground to provide usable outdoor space for a property where the available ground is either uneconomical or impractical to terraform. Decking can be limited to a small strip bordering the home or an expansive, multi-level complex.

These platforms can support many outdoor hardscape features such as barbeque islands, counters, bars, fire features, and lounge areas. Outdoor rooms like kitchens and entertainment areas can be supported on a deck, providing ample space for homeowners and guests to enjoy the beautiful coastal California weather.

Decks require a significant amount of support in the form of concrete wells anchored into the hill or cliffside. This can significantly increase the price of installation and maintenance, as even minor earthquakes can cause significant damage to these anchors.

Terraces

Terraces have long been used in mountainous and hilly areas to support greater agricultural production. Residential spaces use the same engineering techniques developed to ensure the integrity of the land they’re sculpted into.

The size of each terrace is determined by the underlying structure and grade of the slope on which it’s situated. Light slopes with highly compacted soil can support terraces that expand to the full borders of the property.

 

Larger terraces can support features like pools, patios, and raised planter areas. The stairwells and pathways that connect each level can add to the general aesthetic of the outdoor space, accentuating its ornate or rustic appearance.

As the grade of the slope increases, more creative solutions are required to open up the space. The size of the terrace decreases while the engineering solutions to reduce soil erosion get more comprehensive.

Despite the shrinkage, these spaces can help open up the space and add to the aesthetic draw of the property. Individual terraces can act as entertainment areas, meditation spaces, and can even contain courts for games like bocce ball or badminton.

Engineering Challenges

The real challenge that comes with construction on mixed topography is engineering. Hillsides can quickly destabilize and liquefy during the wet season or in an earthquake, causing potentially deadly landslides. 

Hillside and cliffside construction requires contractors to use geotechnical reports, and site informed engineering. Proper drainage is essential for preventing liquefaction during weather events. Structural support is provided by a few primary engineering techniques: caissons, foundations and retaining walls, and rip rap barriers.

Caissons

Foundations on level, stable ground are relatively shallow and rest within the parent soil material or bedrock. Building on cliffs or hillsides requires that foundations reach deeper, which requires specialized structures that provide the necessary support but don’t require extensive excavation. 

Caissons are foundational structures composed of steel rebar and concrete that anchor a structure to a stable surface. Bypassing the looser topsoil reduces downward force on the unstable hillside and ensures the structure can stand the test of time.

These foundations are essential in the construction of decks on slopes, as they connect the deck posts and beams to a structurally sound foundation. To determine the depth of the parent soil material, a geotechnical report needs to be completed and solutions for these foundations need to be engineered accordingly. 

Retaining Walls

Retaining walls are an integral part of hillside construction. Natural forces like gravity, wind, and precipitation all exert significant force on your property’s soil. Over time, this will erode and shift the ground, creating a more unstable environment.

Retaining walls allow for the creation of leveled terraces. These leveled areas help slow water runoff and prevent erosion. Drainage behind the retaining walls collects precipitation and moves it through the drainage system rather than solely along the slope’s soil surface. The leveled terraces create more usable space by cutting into the slope and filling to level. These leveled areas become patios, planting areas and gathering spaces with many use cases. 

Rip Rap Barriers

Water represents one of the biggest dangers to a graded construction. Water loosens up the soil, liquefies it, and increases its weight to the point that it can cause land and mudslides.

Similar to how sandbags are used to help redirect water away from structures during a flood, riprap barriers are used to create a functional area that can complement the aesthetics of a landscape. Ripraps use interlocking rocks or boulders to level the ground and slow water runoff to help protect slopes from erosion. 

Construction Equipment Access

Construction equipment like heavy machinery and cranes are all necessary for major hillside construction projects. On more level properties, access for these machines is as simple as driving them through the side of the yard.

For topographically challenging properties, a more involved solution is necessary. Machines will likely need to be swung in using a crane, which requires additional permitting and skilled workers on-site. 

Despite the challenges, Torrey Pines Landscape Company has decades of experience designing and constructing hill and cliffside landscapes that make the most of the available land. If your property has a steep slope, you don’t need to settle for anything less – call today!