How To Build a Concrete Sitting Wall

A concrete sitting wall is an excellent addition to any outdoor space, providing both functionality and aesthetic appeal. This versatile feature can define garden borders, create extra seating, and enhance the overall look of your backyard or patio. 

Building a concrete sitting wall is a manageable do-it-yourself (DIY) project that can be completed with the right tools and materials. This Old House Senior Technical Editor Mark Powers demonstrates how to construct a durable and attractive concrete sitting wall using cast concrete blocks.

Planning Your Concrete Sitting Wall

Before you begin construction, carefully plan your concrete sitting wall.

Choosing the Location

Sitting walls are best placed around areas you already gather naturally. Consider these factors when deciding where to place your sitting wall.

• Amount of sunlight the area receives
• Nearby landscape features
• Proximity to your patio or living area
• Views from the seating area

Determining Dimensions

The dimensions of your sitting wall will depend on your specific needs, available space, and cast concrete blocks. Generally, consider these guidelines.

• Height: 18–24 inches for comfortable seating
• Width: 12–18 inches for the cap stones
• Length: As needed to accommodate your desired seating capacity

Gathering Materials and Tools

Collect the necessary materials and tools before starting. You’ll need:

• Brick hammer
• Cast concrete blocks
• Concrete sealer
• Hand tamper
• Level
• Mason’s chisel
• Mason’s line
• Masonry construction adhesive
• Paver base (crushed stone and stone dust mix)
• Rubber mallet
• Shovel
• Stakes
• Stone dust

Preparing the Foundation for a Concrete Wall

Don’t be tempted to rush the preparation—a solid foundation is crucial for the stability and longevity of your concrete sitting wall.

Step 1: Marking the Layout

1. Place a concrete block at each end of the planned wall.
2. Drive stakes around the sides of the blocks, leaving at least 1 inch of space.
3. Tie a level mason’s line between the stakes to use as a digging guide.

Pro tip: Notch the stakes where the mason’s line should rest to help keep it in place as you dig.

Step 2: Excavating the Trench

1. Dig the trench, removing the topsoil until you reach the lighter subsoil.
2. Ensure the trench is at least 6 inches deep.
3. Use the mason’s line to keep the bottom of the trench level, adjusting for any slope in the ground. This may mean the trench is shallower in some areas than others.

Step 3: Installing the Base Material

1. Line the trench with paver base material.
2. Tamp down the paver base in 3-inch layers.
3. Continue adding and tamping until the shallowest part of the trench can accommodate half the height of one block plus 1 inch.
4. Spread a 1-inch layer of stone dust over the paver base.

Building the Concrete Sitting Wall

With the foundation prepared, you can now begin constructing your concrete sitting wall.

Step 4: Laying the First Course

1. Set the first concrete block at the shallowest point of the trench.
2. Check that the block is level in all directions: side to side, front to back, and corner to corner.
3. Tap the block into place with a rubber mallet.
4. Continue laying blocks, butting them against each other.
5. Check each block for level and adjust as needed.
6. Once the first course is complete, backfill the extra space around the outside with stone dust and dirt to prevent tilting as the soil settles.

Pro tip: Drop the first course of blocks straight down onto the base to avoid dragging stone dust into the joints.

Step 5: Adding Subsequent Courses

Start the second course with a half block to create a staggered joint pattern for increased stability. Staggering joints adds strength and prevents cracking over time.

1. Score a block down the middle with a mason’s chisel, then split it along the score line.
2. Clean the edges of the split block with a brick hammer.
3. Apply a bead of masonry construction adhesive along the top of the first course.
4. Lay the second course of blocks, ensuring they’re level and properly aligned.
5. Continue staggering joints and gluing every other layer for added stability.

Step 6: Capping the Wall

1. For the final layer, turn the cap blocks perpendicular to the wall to create a wider seating surface.
2. Ensure the cap stones are level and evenly spaced along the wall.
3. Secure the cap stones in place with masonry adhesive.

Finishing Touches and Maintenance for a Concrete Sitting Wall

After completing the construction of your concrete sitting wall, there are a few final steps to ensure its longevity and enhance its appearance.

Curing and Sealing

Allow the masonry adhesive to cure for at least 24 hours before using the sitting wall. This curing time ensures that the compounds reach their full strength, providing a stable and durable structure. You may also want to apply a concrete sealer to help keep moisture out.

Landscaping Around the Wall

Thoughtful landscaping integrates the wall with your outdoor space, creating an inviting ambiance. Enhance the appearance of your new sitting wall by incorporating landscaping elements.

• Plant low-growing flowers or shrubs along the base of the wall.
• Add mulch or decorative stones around the wall’s perimeter.
• Install landscape lighting to highlight the wall at night.
• Place weather-resistant cushions or built-in planters atop the wall.

Maintaining Your Concrete Sitting Wall

To keep your sitting wall looking great for years to come, follow these maintenance tips.

• Regularly inspect the wall for any signs of damage or shifting.
• Clean the surface periodically with a mild detergent and water to remove dirt or algae.
• Reapply a concrete sealer every few years to protect against moisture and staining.
• Fill any cracks or chips promptly with epoxy or concrete filler to prevent further damage.