How to Build a Flagstone Wall

Lead Image for How to Build a Flagstone Wall
  • 8-40 hours
  • Intermediate
  • 200-2,500
What You'll Need
Drinking water
Sunscreen lotion
Thread or rope

A flagstone wall is very easy to build and helps demarcate areas within your garden, enhancing the beauty of the landscape. Made from light flagstones, this type of wall resembles a stacked slate and does not require any drainage system. A flagstone retaining wall is usually no more than 3 to 4 feet high and is used to retain soil in the garden.

Building a flagstone wall for your garden can be completed in a few hours. However, make sure you have adequate protection from the sun if the weather is hot since you will be working outdoors.

Step 1 – Select Area and Insert Sticks

Select the area for your flagstone retaining wall. Insert two sticks in the soil, at both ends of the wall. Make sure the sticks are as high as your wall will be and tie a rope or string at both ends of the sticks. This will give you a general idea of how your wall will look and will help keep it even.

Step 2 – Dig the Base for the Flagstone Wall

For a retaining stonewall, use a shovel that is roughly a foot wider than the height of your wall. Flagstones come in very large pieces, so one rock for the depth measurement will suffice. Dig the trench at least 10 to 12 inches in the soil.

Make sure the hill you want to retain slopes back gradually about an inch per rising foot and add or remove dirt to it accordingly. Try to maintain the slope throughout the length of the flagstone wall.

Step 3 – Add Gravel to the Trench

Add gravel to the trench and rake it so it is aligned with the ground. The gravel will help secure the base of the flagstone wall.

Step 4 – Lay the Stones

Begin laying the stones, using the largest ones first, and cover the area of the gravel underneath. Make sure the stones are placed securely and do not wobble. Save some large stones for the top layer.

Step 5 – Cover the Joints

Step back to review the wall and make sure it does not wobble. You can leave the joints bare or insert small chips of the stone into them. You can also mix soil and water to achieve a mortar-like consistency and insert it into the gaps. This will allow small plants or grass to eventually grow there, thus enhancing the charm of your flagstone wall.

Step 6 – Finish the Top

You can leave your wall as it is, or add large stones to the top layer to make it sturdy and give it a finished look. Apply a layer of concrete or mortar to the next to the last layer of stone and gently place the top stones on it. Insert small stones or soil into the gaps, or insert broken chips of flagstones. This will make your wall more secure along with giving it a more rustic look. Remove the sticks and thread or rope.

Your flagstone retaining wall is now complete.