Window box planters are a nice way to accentuate the curb appeal of your home. A full window box planter is surprisingly heavy. Thus, it is a good idea to purchase or build a window box with brackets. The brackets will help distribute the weight evenly, reducing the stress on the wall studs and mounting screws. When installing on wood or siding, use standard 3-inch lags for mounting. If you are mounting to brick, purchase wall anchors. The lag screws will mount to the anchors, expanding the anchor inside the brick and providing a secure, long-lasting mount.
Locate the studs under the window inside the house with a stud finder. Generally, studs are at each end of the window. Mark the stud location on top of the window sill so that you will see the mark when you are outside the window.
Go outside and measure 1 inch below the exterior window sill where you have the stud marks. Place the top of a bracket even with the 1-inch mark. Use a level on the side of the bracket to make the bracket even and straight.
Mark the mounting holes from the bracket to the wall with a pencil. Repeat the marking process for the opposite side of the window.
Drill pilot holes in the exterior wall for the mounting screws. If you are installing on brick, make holes the same size as the brick anchors. When installing on wood or vinyl siding, drill holes slightly smaller than the lag bolts you are using to mount the window box.
Insert the wall anchors, if this is a brick installation. Tap the wall anchors into the wall with a hammer. Insert lag bolts with washers into each mounting hole in the brackets. Place each bracket on the wall and screw in the lag bolts halfway into the mounting holes in the wall with a socket wrench.
Place the level against the side of each bracket to ensure the bracket is straight. Secure the bracket to the wall by tightening the lag bolts completely.
Place the window box planter on top of the brackets and position the box even over the end of each bracket. Drill pilot holes 2 inches under the top edge of the box where the box meets the bracket.
Install 2½-inch decking screws to secure the window planter box to the brackets. Fill the box with soil and plants.