How do I fix a letterbox that is loose or draughty?

A letterbox is two plates bolted through a hole with a sprung flap. Almost everything that goes wrong with one is a loose bolt or a tired spring.

What you'll need

• Screwdriver to suit the bolts, usually a large flat or Phillips
• A brush-type letterbox draught excluder
• Threadlock or a rubber washer

Step by step

1. Look at it from the inside.Almost every letterbox is two plates joined by two bolts passing through the door, with the nuts or the fixing heads on the inside. That is where the adjustment is.
2. Tighten the bolts evenly.Both sides a little at a time rather than one fully first. Uneven tightening twists the outer plate and can crack it, particularly on plastic.
3. Do not overtighten on uPVC.The door skin is thin and the bolts pull through if forced. Firm is enough — the plate should not move, and any more risks the door rather than the letterbox.
4. Stop them working loose again.A drop of threadlock, a nylon locking nut or a rubber washer under the head. Door vibration is what loosens them, and any of the three stops it recurring.
5. Check the bolt holes are not enlarged.Years of movement wear the holes oval, so the bolts never grip. Larger diameter bolts, or a repair plate spreading the load, fixes it.
6. Check whether the flap spring has gone.A flap that hangs open or closes slowly has a failed spring. Some are replaceable individually; on most modern letterboxes the whole unit is easier to replace.
7. Measure before buying a replacement.The aperture size, the hole centres and the door thickness. Getting a letterbox with the same hole centres means no new drilling.
8. Fit an internal draught excluder.A brush-and-flap unit screws over the opening on the inside. It costs very little and it is by far the most effective single fix for a draughty letterbox.
9. Choose brush over flap alone for exposed doors.Brush seals close around the post as it comes through, so they keep sealing while the door is being used. A rigid flap alone slams and leaks at the edges.
10. Seal around the outer plate.A thin bead of clear silicone around the top and sides of the outer plate, leaving the bottom open to drain. It stops wind-driven rain tracking into the door core.
11. Check the door itself for movement.If the whole door rattles, the letterbox is not the real problem. Adjusting the keeps or fitting draught seal to the frame deals with the actual gap.
12. Lubricate the hinge and spring.A little dry lubricant on the pivot. A stiff flap that has to be forced is what eventually breaks the spring or loosens the fixings again.
13. Consider security while you are there.A letterbox close to the lock is a known risk. A cowl or a restrictor plate on the inside prevents anyone reaching through, and costs very little.

Tips

• The fix is almost always two bolts on the inside. Tighten them evenly and add threadlock.
• A brush draught excluder on the inside is a few pounds and stops the draught completely.
• Do not overtighten on uPVC — the bolts pull straight through the door skin.

Common mistakes

• Tightening one bolt fully before the other — It twists the outer plate against the door and can crack it, especially on plastic or a painted timber door with a slightly uneven face.
• Sealing all the way round the outer plate — Any water that does get behind it then has no escape and sits in the door core. Leave the bottom edge unsealed so it can drain.

If it doesn't work

Questions people ask