The size of the hole(s) in the light fixture will determine the size of the wedge anchor that should be used. When using a wedge anchor, the hole size to be drilled into the concrete should be equal to the diameter of the wedge anchor. The hole in the light fixture needs to be slightly larger than the diameter of wedge anchor being used. For example, if the hole in the light fixture is 5/16" then a 1/4" wedge anchor should be used.

The length of the wedge anchor to be used can be determined by adding the thickness of the material being fastened to the minimum embedment for the diameter of anchor being used plus any space needed for the nut and washer. This will provide the minimum length of anchor to be used. Generally, the best holding values are obtained with deeper embedment into the base material. However, the deeper the concrete is penetrated, the more likely that rebar may be encountered during installation. If the light fixture is to be placed outdoors, stainless steel wedge anchors should be used since stainless steel is rust resistant.

Below are step by step instructions outlining how to use wedge anchors to fasten a light fixture to concrete:

1. Place the light fixture on the concrete. Mark where these holes are on the concrete. You can also use the light fixture as a template and hold it in place and then drill these holes. Either method is acceptable.

2. When drilling into concrete, always use a hammer drill. Using a hammer drill is the most effective way to ensure that the hole size for the concrete fastener is accurate, which is critical for obtaining holding values.

3. Once the holes are drilled, clean out any debris that was created during the drilling process using a wire brush, vacuum or compressed air.

4. Place the nut and washer on the end of the wedge anchor to protect the threads during installation.

5. With the light fixture in place, insert the wedge anchor through the holes in the fixture and into the concrete. Tap lightly until a minimum of 6 threads is below the surface of the light fixture.

6. Hand tighten the nut until snug.

7. With a wrench, turn the nut 3-4 times until tight or until it meets the recommended torque value for the diameter of wedge anchor being used.

When installing and fastening light fixtures into concrete, a wedge anchor is an excellent choice due to its consistent holding values, easy installation and variety of material types that are available.