Letterplates Buying Guide
Written by Cornwall Composite DoorsReviewed by Cornwall Composite Doors installersLast updated July 20266 minute read
Short answer
Choose a letterplate that is fully sealed with twin brushes and a sprung, weighted inner flap so it doesn't let in draughts or rain, sized to Royal Mail's 260×40mm standard, and ideally TS008 anti-fishing tested for security. In exposed coastal areas, a heavier flap and a marine-durable finish matter more than usual.
A letterplate is a deliberate hole cut through an otherwise well-insulated, well-sealed door, so it deserves more thought than most buyers give it. Get the wrong one and you'll feel a draught every time the wind picks up off the sea.
Sizing to Royal Mail's standard
The standard letterplate aperture is 260 × 40mm, sized to Royal Mail's own specification and large enough to take an A4 magazine without folding. Wider 13-inch newspaper apertures exist for broadsheets and mail-order packets, and remain fully sealed despite the larger opening.
Keeping draughts and rain out
A good letterplate uses twin nylon brushes on the outer flap and a separate spring-loaded inner flap, with a fully gasketted surround where the plate meets the door. Done properly this should add less than 0.05 to the door's overall U-value — in other words, barely measurable.
In exposed parts of Cornwall, wind loading on a letterplate is genuinely higher than inland, so a heavier weighted flap is worth specifying as standard rather than an upgrade, particularly on west-facing or coastal-facing doors.
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Security: letterbox fishing
Letterbox fishing — using a hook or rod through the letterplate to grab keys left near the door — is a genuine and known burglary method. A TS008-tested letterplate with an internal restrictor blocks this attack, and an anti-arson version adds a metal shroud that stops lit material or liquid being posted through, which some insurers require on rental properties.
Finish choice
Letterplates are typically available in chrome, forged black, pewter, satin and brass, and should match your handle and knocker finish. Pewter's mottled, hand-finished texture suits period and cottage colours like Chartwell Green or Sage, while forged black is the most common pairing with anthracite or French Navy doors.
Alternatives to a letterplate
Some homeowners now choose a completely solid door with no letterplate at all, paired with a wall-mounted post box beside the porch. This removes the biggest single hole in the door entirely and can be a good option on very exposed or high-security properties.
Frequently asked questions
Will a letterplate let in draughts in winter?
Not if it's fitted correctly. A twin-brush outer flap plus a sprung, gasketted inner flap should keep draughts to a negligible level even in exposed coastal locations, though a cheap unsealed plate will let noticeable cold air through.
What's an anti-vandal letterplate?
It's a letterplate fitted with an internal metal shroud that prevents lit material or liquid being pushed through the opening. Some insurers require this on let or unoccupied properties as a fire-safety condition.
Can I have no letterplate at all?
Yes. A solid door with a separate wall-mounted post box is increasingly common, and removes the largest deliberate opening in the door entirely, which some homeowners prefer for both security and thermal performance.
Does a bigger letterplate let more cold air in?
Slightly, but a well-sealed 13-inch newspaper letterplate still performs close to a standard 10-inch one, because the seal quality matters far more to heat loss than the aperture size.
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