Quick answer
Composite doors contract slightly in cold weather, the opposite of summer expansion, which can leave a previously snug door feeling loose, draughty, or slightly rattly with a wider gap at the frame. It's normal seasonal movement, but combined with stiffened lock lubricant and Cornwall's winter storms, it's the season we see the most draught and rattling complaints.
Overview
In winter the slab contracts slightly and the seal stiffens. If the door was well-sealed in summer, you may lose compression in December. Compression adjustment brings the door tighter to the frame.
Symptoms
- Draughts in cold weather.
- Rattle when it's windy.
- Whistling.
Common causes
- Normal thermal contraction.
- Aged seal that has lost its bounce.
The other half of the seasonal movement cycle
Just as a composite door expands in summer heat, it contracts as temperatures drop through autumn and winter, typically by the same 2 to 4mm range but in the opposite direction. Where summer problems tend to be about tightness — catching, stiff locking — winter problems tend to be about looseness: a door that rattles slightly in its frame, feels less snug when closed, or lets in a draught that wasn't there in warmer months.
This is genuinely normal seasonal behaviour and, on its own, doesn't indicate a fault. It becomes a problem worth addressing when the contraction is enough to compromise the weatherseal's compression to the point of letting in real draughts or, in exposed conditions, wind-driven rain.
Why winter also brings mechanical stiffness, not just looseness
Confusingly, winter can also bring the opposite symptom — a stiff lock or handle — but for a completely different reason than summer stiffness. Cold weather thickens old or degraded lock lubricant, making the cylinder and gearbox mechanically harder to operate even though the door itself has contracted and technically has more clearance. This is why 'stiff in winter' and 'stiff in summer' need different diagnoses: one is about the door being physically too tight (summer, expansion), the other is about aged lubricant inside the mechanism (winter, viscosity).
A quick way to separate the two: if the key and handle feel gritty or need real effort even with the door standing open, away from the frame entirely, that points to lubrication rather than seasonal door-size changes.
- Door rattles or feels loose against the frame: seasonal contraction, likely needs compression reset.
- Handle/key stiff even with the door open: lock lubrication issue, not a sizing issue.
- Draughts appearing that weren't there in summer: contraction reducing seal compression.
Cornwall's winter storms make contraction problems more noticeable
A door that's a little loose in its frame is a minor annoyance inland, but on an exposed Cornish coastline facing a winter Atlantic storm, that same small amount of extra clearance is enough to let in genuine wind-driven rain and turn a rattle into a real water-ingress problem. This is why we see a distinct spike in winter call-outs specifically from coastal postcodes — Porthleven, Mousehole, the north coast around Bude — where storm exposure amplifies what would otherwise be a barely-noticeable seasonal change.
For properties on very exposed elevations, it's worth having compression settings checked ahead of the winter storm season rather than waiting for the first bad weather event to reveal a problem.
How compression adjustment compensates for contraction
The compression cam on a three-way hinge controls how firmly the closed door presses against the seal, and it has enough range to compensate for a reasonable amount of seasonal contraction — tightening the compression setting slightly in winter restores good seal contact even though the slab itself has shrunk marginally. This is a routine, low-cost adjustment when caught early, rather than something requiring parts replacement.
It's worth noting this is the opposite adjustment direction to what's typically needed to fix summer tightness, which is exactly why a door set with a sensible seasonal margin — rather than tuned to one extreme — copes better with the full year's temperature range without needing readjustment every few months.
Why draughts alone don't always mean the seal has failed
It's a common assumption that any winter draught means the weatherseal itself needs replacing, but a genuinely healthy seal that's simply not being compressed quite enough — because the door has contracted slightly — will draught just as noticeably as a worn seal would, without actually being faulty. Replacing a perfectly good seal in this situation wastes money without fixing the underlying compression issue.
This is why a proper winter draught diagnosis includes the same paper-slip compression test described for general sealing problems, checked in the cold weather itself if possible, before concluding the seal — rather than the setting — needs attention.
An example from an exposed cottage near Bude
A cottage near Bude, directly facing the prevailing Atlantic weather, developed a noticeable draught along the bottom of the door every winter that the owner had put down to an ageing seal, replacing it the previous year with no lasting improvement. A cold-weather paper test showed the seal itself gripping well everywhere except right at the bottom, where seasonal contraction had reduced compression just enough to let air through. A winter compression cam adjustment — tightening the setting slightly to compensate — resolved the draught without needing to touch the seal again.
How winter shrinkage progresses through the season if left unaddressed
A door that rattles or lets a draught through in early winter, when the shrinkage is still mild, tends to worsen as the season deepens — by January or February, after the coldest, driest spells, the gap between slab and frame can be at its widest of the year, and a rattle that was a minor nuisance in November can become a genuine draught and noise problem by midwinter. Because this is a seasonal, cyclical issue rather than a one-off fault, leaving it every year without adjustment means going through the same discomfort annually rather than correcting the compression setting once properly.
Frame behaviour in granite and cob properties during cold snaps
Older Cornish properties with granite or cob surrounds behave differently to modern cavity-wall openings when temperatures drop: stone and cob both lose a small amount of moisture content in prolonged cold, dry weather, which can very slightly shrink the opening itself rather than just the door. This sometimes means a door that seems to need loosening (because it's shrunk) actually needs the frame checked too, since in a small number of cases the frame has moved enough to overstate how much the door itself has changed.
Guarantee and CERTASS position on cyclical seasonal faults
Because winter shrinkage and summer expansion are cyclical and expected to some degree, most manufacturer guarantees don't treat a normal seasonal gap as a defect — cover is usually reserved for gaps or draughts that persist regardless of season, which points to a hardware or installation fault rather than ordinary material behaviour. As a CERTASS registered installer, our compression adjustments to manage seasonal movement are recorded as maintenance work rather than warranty claims, but if a door's seasonal swing seems unusually large compared with similar doors, we'll flag that as worth investigating as a possible original fitting issue.
Best timing for a compression adjustment aimed at winter comfort
The most effective time to have compression adjusted for winter is early-to-mid autumn, once the door has settled from any summer expansion but before the first serious cold snap, giving us a realistic baseline to adjust from. Adjusting too early, while the door is still slightly swollen from summer, risks over-tightening once the slab shrinks fully in December, while waiting until deep winter to book means living with the draught for weeks before an appointment can be fitted in during our busiest seasonal period.
Typical repair costs in Cornwall
| Work | Typical price | Notes |
|---|---|---|
| Winter compression check and paper-slip test | £65–£95 | Diagnoses contraction versus a genuine seal fault |
| Compression cam adjustment for winter | £90–£140 | Standard fix for seasonal looseness or draughts |
| Lock cylinder clean and re-lubricate | £75–£95 | Where stiffness is from cold-thickened lubricant |
| Seal replacement (where genuinely worn, not just under-compressed) | £150–£260 | Only where the paper test confirms real seal failure |
Guide prices only — we confirm the cost after seeing the door.
When to call a professional
- Compression adjustment or seal replacement.
Prevention
- Silicone-treat seals in autumn.
