In this video, This Old House general contractor Tom Silva shows how to securely fasten outdoor containers to masonry.
Steps for attaching window boxes to brick siding
1. Measure and mark the center of the window. Then measure down from the sill the recommended distance and mark the center of the two mounting holes.
2. Use a hammer-drill and ½-inch-diameter carbide-tipped masonry drill bit to bore holes into the brick. Drill the holes slightly deeper than the plastic wall anchor you’ll be using.
3. Tap a plastic wall anchor into each hole with a hammer.
4. Fasten each mounting bracket to the brick wall with a lag screw. Use a box-end wrench to tighten the lag screw into the wall anchor.
5. To install the window box, simply clip it onto the two mounting brackets.