Boulder Retaining Wall: What You Should Know

A boulder retaining wall can add structure and definition to your landscape design. Unlike a concrete block retaining wall, a boulder retaining wall has a natural look that blends with other outdoor features.

Boulder and rock retaining walls can last over 100 years. They are among the longest-lasting landscape structures, surpassing the lifespan of houses and barns. Many historic rock retaining walls, such as Hadrian’s Wall built in 122 C.E., are still in use today.

This article will guide you through everything you need to know about boulder or large rock retaining walls. With this information, you will be able to decide if this rugged wall form is a good option for your home landscaping.

A boulder retaining wall is a rugged wall made of large rocks. It is used to prevent soil erosion and stabilize slopes. These walls are popular in landscape design for their natural and rustic appearance.

They add an element of beauty and charm to any outdoor space.

When constructing a boulder retaining wall, it’s important to consider several factors. First, you need to choose the right type and size of rocks. The rocks should be large enough to provide stability but not too heavy that they are difficult to handle.

It’s also essential to understand the site conditions and determine the appropriate height and placement of the wall.

One of the key advantages of boulder retaining walls is their durability. They are designed to withstand the test of time and are resistant to weathering and erosion. Additionally, these walls can be easily maintained.

Unlike other types of retaining walls, boulder walls do not require regular upkeep or repair.

Boulder retaining walls also have some disadvantages. One potential drawback is the cost. The materials and labor required to build these walls are often more expensive than other wall types.

Furthermore, boulder walls can be difficult to construct and may require professional assistance.

In conclusion, boulder or large rock retaining walls are a popular choice for home landscaping due to their natural beauty and durability. However, it’s important to weigh the advantages and disadvantages before deciding if this wall form is right for your property. By considering the factors mentioned in this article, you can make an informed decision and create a stunning outdoor space.

A boulder retaining wall is constructed using large rocks or boulders. Unlike other stones, boulders are a specific type of rock. Experts define boulders as rocks or rock fragments larger than 10 inches (25.6 cm) in diameter.

Boulders are excellent construction materials due to their solidity, resistance to weather erosion, and ability to withstand pressure from the soil and minor ground movements.

Advantages and Disadvantages of a Boulder Retaining Wall

Boulders or large rocks are excellent materials for building walls, but they may not be suitable for all home landscapers. Here are some factors to consider:

– Visual appeal: Boulders have a natural beauty and style that can create stunning retaining walls, blending seamlessly into the outdoor environment.

– Durability: The size of boulders makes them resistant to erosion from wind and rain.

– Versatility: Each boulder is unique, allowing you to create distinctive and one-of-a-kind retaining walls that stand out from others.

– Maintenance: A well-built rock retaining wall will require minimal future maintenance.

By considering these factors, you can determine if boulders are the right choice for your landscaping needs.

Cost – Depending on the area, a large rock retaining wall can be a cost-effective option compared to other boulder rock wall styles. The cost of boulders will vary by location and be cheaper where natural boulders are readily available.

Space – Retaining wall boulders are large and can create a massive wall. In small yards, they may not be appropriate due to limited space. Boulder retaining wall construction often requires heavy-duty equipment, necessitating wide entrances into your yard.

Height – Construction limitations of boulder retaining walls restrict their maximum height. If you require a tall retaining wall, a concrete wall is a better option.

Construction – Large boulders may not be suitable for DIY projects due to their size. Their lifting and wall-building process often requires heavy-duty equipment and professional expertise.

Cost – If you live in an area where boulders are scarce, you may face higher costs when procuring these rocks. Additionally, using large boulders for your retaining wall will require professional assistance and specialized equipment, further increasing your expenses.

Construction Method for Boulder Retaining Walls

There are two main types of boulder retaining wall construction: dry-stacking, also known as the gravity method, and using mortar, known as the wet-laid method. Some contractors may only be familiar with one method, so it’s important to communicate with them to ensure you’re on the same page.

The dry stack (gravity) method is a popular and straightforward way to build a rock retaining wall. It relies on the weight of the rocks to retain the wall’s shape, using an interlocking pattern created by specific rock contours, weight, and friction.

This method is suitable if you use heavy boulders and have moisture in the ground. The cracks between the rocks allow water to seep through and relieve pressure behind the wall. This drainage system will maintain the wall structure and increase its lifespan.

Pack small rocks instead of soil behind the wall for better drainage, especially in wet soil or heavy rainfall areas.

Using this method can be difficult as it requires time, patience, and expertise to find rocks that fit together seamlessly and solidly.

Some contractors may use mortar or cement when constructing a retaining wall with boulders for extra strength. This method is suitable for dry environments without moisture buildup in the soil. If you live in a moist environment, you can still build a rock wall with mortar by adding drainage.

All retaining walls require drainage stone behind them to prevent soil pressure. Depending on the water level in your environment, you may need to add drainage pipes or holes to release pressure behind the wall.

The type of mortar is important for this method. Use type “M” or “S” for your project. Type “M” is the strongest with the highest concrete content and mimics the strength of the stone.

Type “S” is suitable for smaller boulder walls and can withstand excessive moisture better than type “M”.

Alternatively, you can use a combination of both methods for a natural look with increased strength. This involves using mortar behind the wall to create the appearance of a dry-stacked wall in the front. You can also use pigmented mortar to match the stones and reduce the visibility of mortar lines.

When constructing boulder retaining walls, consider the type of rocks used.

Fieldstone Boulders: Found on the earth’s surface, fieldstone boulders possess inherent character and age. They often feature moss and dirt due to exposure to outdoor weather conditions. Quarry Boulders: Dug up from the ground, quarry boulders have less age and character compared to fieldstone boulders. With fewer angles, these rocks are easier to work with. They also provide greater stability when building a wall, making them suitable for inexperienced DIY enthusiasts. – These rocks are naturally smoothed by constant running water in rivers, giving them their distinctive rounded shape.

They come in different sizes, including boulders which are ideal for building walls with rounded stones.

Consider these tips to ensure you know all the facts before investing in a retaining wall with boulders:

– Wall Color: Natural rock retaining walls come in a variety of colors such as off-white, pink, orange, gray, black, or reddish. The color of your wall will greatly affect its appearance.

– Wall Pattern: There are two main types of patterns in large rock retaining walls. The first is a modular pattern using boulders of similar size and shape. The second is a random pattern using boulders of various shapes and sizes.

The latter requires more time, planning, and skill to construct.

– Permits: Retaining walls over 4 feet in height usually require permits.

Boulder Retaining Walls: Professional Help

Large boulder retaining walls require professional help due to their weight and size. Hiring a licensed contractor is necessary for the construction process.

The cost of a boulder retaining wall varies depending on several factors. According to HomeGuide, the price range is $2,000-$10,000, with an average cost of $6,000. Boulders are priced at $50-$200 per linear foot or $100-$350 per ton.

For a large boulder wall, the cost is $600 per ton.

Factors impacting the cost include:

– Labor

– Materials

– Size

– Site conditions

– Design complexity

– Accessibility

Consider these factors when determining the cost of your retaining wall.

– Size and Design: The length and height impact the cost of the wall as more materials and labor are needed. The complexity of the design will also affect the cost. A straight wall costs less than a wall with curves, columns, and stairs.

– Foundation and Drainage: Higher walls require deeper foundations. Most mortared walls need some kind of drainage, which increases the cost.

– Labor Costs: Labor typically costs $40-$80 per hour or $10-$30 per square foot.

– Engineered Plans: For walls over 4 feet high, hiring a structural engineer to create plans is necessary.

– Heavy Construction: Depending on the site, clearing the ground, removing old walls, or leveling the site may be required. This will involve heavy equipment and operators.

Boulder retaining walls are a fascinating landscaping feature that adds both functionality and beauty to any outdoor space. If you’re considering having one in your yard, there are various design options to suit your taste and needs.

One idea is a variegated boulder retaining wall. This design features boulders of different sizes and colors, giving the wall a natural and textured appearance. The contrasting hues create visual interest and can complement the surrounding landscape.

Another option is a terraced boulder retaining wall. This design utilizes multiple levels or terraces, allowing for improved water drainage and preventing soil erosion. It also creates a unique and visually appealing look that can be enhanced with the use of plants or other decorative elements.

A stacked boulder retaining wall is a classic choice that never goes out of style. This design involves arranging boulders in a stacked formation to create a cohesive and sturdy structure. It’s a simple yet effective way to retain soil and add character to your yard.

For a more contemporary look, consider a sleek and minimalist boulder retaining wall. This design uses large, smooth boulders to create a clean and modern aesthetic. It’s a great choice for those who prefer a more streamlined and less ornate style.

When choosing a design, it’s important to take into account the size of your yard, the slope of the land, and any other existing landscaping features. Consulting with a professional landscaper can help you determine the best design for your specific needs.

In conclusion, boulder retaining walls offer a versatile and visually appealing way to retain soil and enhance the beauty of your outdoor space. Whether you prefer a natural and textured look or a sleek and modern design, there are options available to suit your taste and needs.

This landscape designer utilized boulders in different colors: red, pink, off-white, and a soft bluish-green. The boulder wall seamlessly integrates into the hill and its surroundings. Plants and flowers were added to soften the appearance of the wall.

This contractor utilized the dry-stack method for the retaining wall, featuring a random pattern where diverse stone sizes fit together like a puzzle. The boulder variety exemplifies the deep orange hues found in fieldstone.

This wall has mortared construction and a mixture of small stones and round boulders, creating a varied stone wall with different shapes and sizes.

Adding a curved boulder retaining wall around a firepit can provide extra seating in your space. Use boulders of similar size for a uniform appearance and ensure that the top is flat for comfortable seating.

Boulders have a unique natural form that combines well with various materials. In this design, the landscaper combined flat, dry-stacked boulders with custom weathered steel.