Quick answer
Wind coming through a composite door on the Cornish coast is usually a seal that would be perfectly adequate inland but is being overwhelmed by genuinely higher wind loads and pressure differentials at an exposed site. The fix is compression adjustment or a coastal-grade seal upgrade, not a sign the door itself is faulty.
Overview
Cornish coastal properties get wind loads two or three times what an inland installation faces. A door that was 'just about sealed' inland will fail near the coast - margins have to be tighter.
Symptoms
- Draught in strong wind, fine in still weather.
- Curtains or doors moving in a closed hallway.
Common causes
- Marginal seal compression.
- Coastal pressure differentials.
- Letterplate flap not closing fully.
Cornwall's wind loading is a different category of problem
Wind speed near open coastline in Cornwall regularly exceeds what an equivalent inland property experiences, and gusting during Atlantic storms can subject a door to pressure loads two or three times higher than a sheltered inland installation ever sees. Doorsets are tested and rated for exactly this kind of performance under the BS 6375 weather performance standard, covering air permeability, watertightness and wind resistance.
A door specified to a standard rating may be entirely adequate a few miles inland yet marginal on an exposed clifftop, headland or estuary-facing plot, simply because the actual conditions it faces are harsher than the baseline the standard rating assumes.
Why 'just about sealed' inland fails at the coast
Seals that hold compression comfortably under normal domestic wind loads can be pushed past their working tolerance by sustained coastal gusting, particularly at the corner diagonally opposite the top hinge where compression is naturally weakest on most mechanisms. What reads as a minor draught inland can read as genuine wind coming through the door on an exposed site.
This isn't usually a sign of poor original installation - it's a sign the margins that work fine in most of the country are tighter than they need to be for a genuinely exposed Cornish position.
What to check
Feel around the entire perimeter during strong wind rather than on a calm day, since the fault often only manifests under load. Check that the letterplate flap is returning fully to its closed position and not being held slightly open by wind pressure or a worn spring.
If the wind noise or draught is worse from one direction specifically, that points toward the seal on the corresponding side of the door rather than a general perimeter issue.
Options for exposed properties
Compression adjustment is the first and cheapest step, and resolves many cases on its own. Where that's not enough, a heavier, storm-rated seal profile - thicker gauge, better memory under sustained load - is available for exposed properties and is a straightforward retrofit into the existing groove in most cases.
For newer installs or full replacements on genuinely exposed sites, specifying a door tested to a higher BS 6375 rating from the outset avoids the problem altogether rather than fixing it after the fact.
Twice-yearly checks for coastal properties
We recommend coastal properties have compression checked twice a year rather than the two-to-three-year interval that's fine inland - once before the main autumn storm season and once in spring to catch any drift that's crept in over winter.
This is a five-minute check when combined with any other maintenance visit and catches problems while they're still a free adjustment rather than a paid seal replacement.
Typical repair costs in Cornwall
| Work | Typical price | Notes |
|---|---|---|
| Compression adjustment | £75 | First step for most cases |
| Storm-rated seal upgrade | £140-£220 | For genuinely exposed coastal properties |
| Twice-yearly maintenance check | £60-£90 | Recommended for coastal properties |
Guide prices only — we confirm the cost after seeing the door.
When to call a professional
- Compression adjustment or coastal-grade seal upgrade.
Prevention
- Coastal properties: check compression twice a year.
