Mailboxes come in a variety of shapes and sizes. They are made from several types of materials as well. Although they are meant to keep your incoming mail dry and secure, mailboxes sometimes develop leaks. Because they are exposed to the weather at all times, rain water quickly settles inside your mailbox. Repairing a leaking mailbox is much like preventing leaks around windows and doors on your home. Most leaks occur around the fasteners securing the mailbox together and to the platform where it attaches.
Check the mailbox door for bends, if you have a metal mailbox. Bends prevent the door from closing securely and allow rain to enter. Bend the door straight with your hands until the door closes securely. If you have a plastic or resin box that has a warped door, purchase a replacement door.
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Open the mailbox door and inspect the screws or nails securing the bottom of the mailbox to the platform. Tighten screws with the appropriate screwdriver or hammer loose nails. Apply silicone caulk over each screw and nail head with a caulking gun.
Apply a bead of caulk on the inside bottom edge between the sides and the rear of the mailbox with the caulking gun. This helps to prevent water that settles on the platform from seeping inside the mailbox.
Caulk around screw and nail heads on the outside top and sides with the silicone caulk and caulking gun. Loose screw and nail heads allow water to seep through. Caulking seals the holes and helps keep the mailbox dry inside.
Fill any cracks on the mailbox with caulk, if you have a plastic or resin one-piece mailbox.