How to Build a Mortared Stone Garden Border Step-by-Step

Creating a mortared stone garden border is an excellent way to add structure, elegance, and durability to your outdoor space. Unlike dry-stacked stone borders, a mortared stone border offers increased stability and longevity, effectively containing soil and plants while withstanding weather conditions for years to come. Whether you want to define flower beds, separate garden areas, or create visual interest, building a mortared stone border can be a rewarding DIY project.

In this detailed guide, we’ll walk you through the process step-by-step, covering everything from planning and materials to laying the stones and finishing touches.

Why Choose a Mortared Stone Border?

Before diving in, it’s helpful to understand why a mortared border might be the right choice:

• Durability: Mortar bonds stones firmly together, resisting shifting or settling.
• Aesthetic Appeal: Mortar allows for precise shaping and neat lines.
• Customization: You can select different stone types and mortar colors.
• Weed Prevention: A solid mortar joint reduces weed growth between stones.

With these benefits in mind, let’s explore how to build your own.

Materials and Tools Needed

Materials

• Natural stones (flagstone, fieldstone, or any preferred landscaping stone)
• Portland cement
• Masonry sand
• Hydrated lime (optional, improves mortar workability)
• Water
• Gravel or crushed rock (for base)
• Landscape fabric (optional, for weed barrier)
• Concrete bonding agent (optional)

Tools

• Shovel
• Tape measure
• Level (preferably a long one)
• Wheelbarrow or mixing tub
• Hoe or mixing paddle
• Trowel
• Pointing tool or mortar jointer
• Rubber mallet
• Garden hose or bucket for water
• Gloves and safety glasses

Step 1: Plan and Design Your Border

Start by deciding where your garden border will go. Use spray paint or a garden hose to mark the outline on the ground. Consider:

• The desired height, most garden borders range from 6 inches to 18 inches.
• The thickness, typically one stone thick (about 6-8 inches).
• The shape, straight lines or gentle curves depending on your garden style.

Take measurements of the total length to estimate materials needed. For example, if your border is 20 feet long and 8 inches high with stones roughly 4 inches tall, you can calculate the number of stones accordingly.

Step 2: Prepare the Ground

Proper preparation ensures your wall will last.

1. Clear the area: Remove grass, plants, rocks, and debris from the marked area.
2. Dig a trench: Excavate a trench about 6 inches deep and as wide as the stone thickness plus about 4 inches extra for working room. For example, for an 8-inch stone wall, dig a trench approximately 12 inches wide.
3. Add landscape fabric: If desired, lay landscape fabric at the bottom of the trench to inhibit weed growth.
4. Create a compacted base: Pour about 3-4 inches of gravel or crushed rock into the trench. Compact it firmly using a tamper or simply by pressing down. This helps with drainage and prevents settling.

Step 3: Mix Your Mortar

Mortar is made by combining Portland cement, masonry sand, water, and sometimes hydrated lime.

Basic Mortar Mix Ratio

A common ratio is:

• 1 part Portland cement
• 3 parts masonry sand
• (Optional) A small amount of hydrated lime for workability

Mixing Instructions

1. In a wheelbarrow or mixing tub, combine dry ingredients thoroughly.
2. Slowly add water while mixing with a hoe or mixing paddle until you reach a firm but spreadable consistency, similar to peanut butter.
3. Avoid overly wet mortar; it should hold its shape when pressed.

If using concrete bonding agent (recommended when laying new mortar against old), follow manufacturer instructions.

Step 4: Lay the First Course of Stones

The first layer is critical because it sets the foundation for the entire border.

1. Apply mortar base: Spread about an inch of mortar evenly along the gravel base within the trench using your trowel.
2. Place stones: Set each stone firmly into the mortar bed with slight twisting motions to ensure good adhesion.
3. Check level: Use your level frequently to keep stones even horizontally and set them flush with each other vertically.
4. Tap gently: Use a rubber mallet to adjust stones without damaging them.
5. Leave space for joints: Maintain consistent joint width between stones (usually about 1/2 inch) for mortar filling.

Wait about half an hour after placing the first course before adding additional layers so that this foundational layer has time to set slightly.

Step 5: Build Up Additional Courses

Once the first course is stable:

1. Butter each stone’s bottom and sides with mortar before setting it on top of lower stones.
2. Stagger joints: Offset vertical joints from one row to the next (like bricks) to increase stability.
3. Use smaller stones as needed to fill gaps or create tighter fits.
4. Regularly check level and alignment both horizontally and vertically.
5. Fill joints completely with mortar as you go by applying it with your trowel or pointing tool.

Continue stacking courses until reaching your desired height.

Step 6: Tooling the Joints

Once you have laid several courses or finished building:

1. Allow mortar joints to begin curing but remain soft enough for tooling (usually after about an hour).
2. Use a pointing tool or jointing tool to smooth and compress mortar joints , this improves appearance and weather resistance.
3. Remove excess mortar from stone faces quickly before it hardens using a brush or damp sponge.

Tooling adds professional polish while helping prevent moisture infiltration.

Step 7: Clean Up and Cure

Proper curing helps your wall gain strength:

1. Lightly mist the completed wall with water once every day for 3-5 days (avoid overwatering).
2. Protect fresh mortar from direct sun or frost by covering loosely with plastic sheets if needed.
3. Clean any remaining mortar residue on stones gently once fully cured, using mild detergent and soft brushes if necessary.

Additional Tips for Success

• Select durable stones suitable for outdoor use; avoid soft sedimentary rock prone to crumbling.
• Wear gloves and eye protection when mixing and working with cement-based products.
• Work in manageable sections instead of trying to build very long walls all at once.
• Consider adding decorative caps on top of your border established with flat stones laid with minimal mortar spread.
• If creating curves, use smaller stones that can be adjusted more easily than large flat pieces.

Conclusion

Building a mortared stone garden border is an achievable DIY project that enhances both aesthetics and functionality in your garden space. By carefully planning your layout, preparing a solid base, mixing quality mortar, thoughtfully placing each stone course, and finishing joints neatly, you’ll create a beautiful border that lasts many years.

Remember that patience and attention to detail during each step are key, but don’t hesitate to experiment with different stone shapes and arrangements that suit your personal style! With this step-by-step guide as your foundation, you’re ready to transform your garden edges into stunning stone features that impress season after season.