Quick answer
Rain penetration around a composite door in Cornwall almost always comes from failed frame sealant, a missing or damaged head drip cill, blocked drainage, or a worn threshold - not the door slab itself. Comparing exactly where water appears inside the property to these known points quickly identifies which one is responsible.
Overview
Driving rain, especially Atlantic squalls, will find any weakness in a doorset. Compare where the water shows up to identify the source.
Symptoms
- Water on floor after heavy rain.
- Wet plaster next to the frame.
- Water only in wind-driven rain.
Common causes
- Failed frame silicone.
- No head drip cill or cill damaged.
- Blocked drainage.
- Threshold worn.
Driving rain finds weaknesses that vertical rain doesn't
Atlantic squalls hit Cornish properties at an angle, driven horizontally by wind rather than falling straight down, which tests parts of a doorset that ordinary vertical rain never touches. A frame that copes fine with a still, heavy downpour can leak visibly the moment the same rain arrives wind-driven from the exposed side.
This is why some customers report leaks that only happen 'in certain storms' - it's not inconsistency in the door, it's a genuine difference in how driving rain versus vertical rain interacts with a marginal seal or sealant joint.
Matching symptom to source
Water on the floor after heavy rain, appearing at the base of the door, points to threshold or drainage. Wet plaster tracking down from above the frame points to a missing or damaged head drip cill. Damp patches to either side of the frame, not at the base, point to failed perimeter sealant against the brickwork.
Establishing which of these three patterns matches your situation before booking a repair saves time and means the right fix gets quoted first time rather than after a process of elimination on site.
Frame silicone: a wear item, not a permanent seal
The sealant joint between frame and wall degrades under UV and thermal cycling, and salt-laden coastal air accelerates that degradation compared with an inland equivalent. Cracked or shrunk sealant is usually visible on close inspection - hairline gaps, sections pulled away from the brick, or a chalky, brittle texture rather than a flexible one.
Re-sealing every five to eight years is reasonable maintenance for any composite door installation and cheaper by far than the redecoration bill that follows a winter of undetected leaks.
Head drip cills: cheap insurance for exposed elevations
A head drip cill throws water running down the wall clear of the frame-to-wall joint rather than letting it track straight down onto it. Many installations, particularly older or budget-specified ones, were fitted without one - fine on a sheltered wall, a real liability on an exposed, rain-facing elevation.
Retrofitting one is a modest job that often resolves a leak that's been wrongly blamed on the seal or frame for years, simply because nobody had checked what was happening above the door.
Drainage and threshold, together
Blocked drainage slots and a worn threshold gasket often occur together, since both are affected by the same grit, salt and foot traffic exposure at the base of the door. Clearing slots is free and quick; a worn threshold gasket or blade typically needs replacement rather than adjustment.
Both should be checked together on any rain-related callout, since fixing one without the other often leaves the underlying leak only partially resolved.
A seasonal check worth doing
Ahead of the autumn storm season, a full perimeter check - sealant, drip cill, drainage, threshold - takes under an hour and catches most problems before they cause damage. This is particularly worthwhile for holiday lets, where nobody may notice a slow leak until it's caused visible damage to flooring or plaster.
Typical repair costs in Cornwall
| Work | Typical price | Notes |
|---|---|---|
| Perimeter diagnosis visit | £75 | Identifies which of the four sources applies |
| Re-sealing (frame to wall) | £95-£180 | Full perimeter |
| Head drip cill fitting | £110-£220 | Where none exists or existing one is damaged |
| Threshold and drainage service | £90-£220 | Gasket replacement plus drainage clear |
Guide prices only — we confirm the cost after seeing the door.
When to call a professional
- Re-siliconing or cill installation.
Prevention
- Re-silicone every 5-8 years.
