How to Install Hardscape Lighting (On a Retaining Wall)
Step #1: Hardscape lighting is a great addition to any outdoor space, as installing such lighting extends your ability to use your outdoor space beyond just the daylight hours. Before you get too far into the project, ensure you have all your tools. You'll need a tape measure, pencil, Philips head screwdriver, masonry chisel, masonry hammer, a 4 inch or 4.5 inch angle grinder with a diamond tip blade attached to it, a hammer drill with a 1/4 inch masonry drill bit, your caulking gun, and a tube of block adhesive.
Step #2: When tackling a hardscape lighting project, the first real step is to measure and mark the locations of each light. Most experts recommend using a spacing of six to eight feet for each light. Once you have everything you need and your light locations are marked, use your masonry chisel to break the glue between the retaining wall's capstone and the stone below.
Step #3: Once you've removed the capstone, set your light fixture on top of the wall in the cavity created by the removed capstone. Mark a line from the central point of the fixture back to the dirt behind the retaining wall. This is where you will score a line for the light's wire. If there are parts of the light fixture that would prevent the capstone from sitting evenly on the top of the wall, mark those areas. Once the position of the light is marked, use your angle grinder to grind out slots to place the fixture in.
Step #4: You can use a hammer drill, masonry bit, and masonry anchors to anchor the light to the top of the wall. Or, you can use your tube of block adhesive to glue the light fixture to the top of the wall on one side and to the bottom of the capstone on the other side. Remember, the light fixture goes between the top of the hardscaped wall and the bottom of the capstone, so the weight of the capstone resting on top of the fixture and pressing it against the wall (along with some glue) may be enough to hold it there. But for peace of mind, most professionals will recommend attaching the fixture with masonry anchors, (though doing so does make the project more labor-intensive).
Step #5: Once your fixture is firmly placed on top of the wall, make sure the fixture is properly wired and ready to connect to the rest of the light fixtures in that series. You may want to test the light and ensure it works before you reinstall the capstone. Once your fixture is double and triple checked, place some block adhesive on the bottom of your capstone, and set it back in place on top of the wall. Give the top of a capstone a good tap with a mallet or hammer to ensure it's snug. Once the adhesive is dry, you'll have a strong, durable hardscaped wall with new lights installed between the top of the wall and the capstones!