How to Fit a Letterbox in a Timber or uPVC Door
Measure, mark, cut and fit a new letterbox in a UK front door, with advice on position, draught excluders, brush seals, security and when to leave it to a joiner.
Replacing a worn letter plate or adding one to a door is a satisfying small job. It is also one that you cannot easily undo: once the slot is cut, it is cut. Careful measuring and marking prevent the common mistakes of a slot that is too low, off-centre or too large for the plate.
Before you cut anything
Consider whether you need a new opening or just a new plate:
- Replacing an existing letterbox. Measure the existing hole and buy a plate that covers it, or one with the same cut-out size.
- Cutting a new opening. Make sure the door type allows it, the position is sensible and the rules for your property are met.
- Leasehold flats and listed buildings. There may be restrictions on altering the entrance door.
- Fire doors. Letterboxes in fire doors need fire-rated products. Do not cut openings in fire doors without suitable letterboxes and advice; flats often have fire doors at the front entrance.
If your door is uPVC or composite, there may be a hollow or insulated core, and cutting could damage it. A specialist is often better in such cases.
Choose the letterbox
- Standard letter plate. Simple flap, often with a spring. Typically 250 to 330 mm wide, 50 to 70 mm high.
- Draught-proof or brush letterbox. Includes a brush seal that reduces draughts. See how to draught-proof doors and windows.
- Restrictor letterbox. Restricts the opening to resist fishing and arson.
- Letterbox with a cage or bag. Collects post inside the house.
Look for a design that matches your door furniture and meets the standard for your insurance or area.
Where to put it
The standard guide is that the top of the letterbox should sit at least 450 mm above the bottom of the door, and many people place it about 100 to 150 mm below the top rail or around waist-to-chest height, to make it comfortable for postal workers. In practice, align it with other door features such as the knocker or handle, and keep it away from locks and hinges. Also check that you leave enough timber around it for strength.
Tools
- Pencil and tape measure
- Spirit level
- Drill with a pilot bit and a larger bit for starting the cut
- Jigsaw or padsaw
- Sandpaper and file
- Screwdriver
- Masking tape to stop splintering
Step by step for timber doors
- Mark the position. Use the cut-out template that comes with the plate, or measure the plate. Use a level to ensure the slot is straight.
- Mask the area. Put tape on both sides to reduce splintering.
- Drill a corner hole. Drill a hole inside the marked rectangle at each corner, big enough for the saw blade.
- Cut. Use a jigsaw or padsaw to connect the holes, working slowly and keeping the saw upright.
- Smooth the edges. File and sand, and then seal the exposed timber with primer or paint to protect against moisture.
- Fit the plate. Insert the barrel bolts or screws through the door, align the plate and tighten.
- Test. Check that the flap moves freely and post will not catch.
Where the door is thick or has panels, check that the cut does not run through mouldings or glazing bars.
Replacing a letterbox on a uPVC door
Most uPVC door letterboxes are held with bolts or screws from the inside. Remove the old one by undoing the fixings, clean the surface and fit the new one with the same hole pattern. Do not cut new openings in uPVC doors unless you know how, since the profile is hollow with reinforcement.
Security considerations
- Keep the letterbox away from the lock and handle.
- Use a restrictor or a fishing guard if there are concerns.
- Do not leave keys or valuable items visible through the opening.
- Consider an internal cage or box to catch mail.
Costs and help
Fitting a letterbox is typically a short handyman task, often combined with other door jobs such as replacing door handles or a lock cylinder. On Compito, you can send a request with your postcode and photos, compare offers from ID-verified local providers, ask questions by message and pay online when you accept.
Frequently asked questions
Can I put a letterbox in a fire door?
Only with a fire-rated letterbox that is suitable for the door and installed as instructed. Ask a competent person.
How big should the slot be?
It should match the cut-out size of the plate you buy, typically listed in the product details. Mark carefully before cutting.
Why is my letterbox draughty?
The flap may not seal. Fitting a brush or draught-proof plate often improves it.