By the FaultToFix team | Published: 28 October 2026 | Last updated: 28 October 2026
Short answer: Most damp-window problems are not broken windows. Streaming bedroom windows in the morning are usually moist room air meeting a cold pane, and a draughty uPVC window is usually a loose locking cam, not a failed seal. Where the water sits — and where the air gets in — tells you which one you have before you spend anything. Find your symptom in the table below, run the free test that confirms it, then follow the guide that matches.
Who this page is for: Homeowners and renters in the US and UK with morning condensation or a cold draught at a window · DIY level: Diagnosis is easy and free; both fixes in these guides are beginner-level, with a clear line where DIY stops · Cost: Every diagnosis on this page costs £0 / $0; the condensation routine costs £0, and the draught adjustment costs £0 unless a seal is genuinely finished
Safety box — read this before any damp-and-windows guide on this site: Nothing here involves opening a sealed glazing unit, removing glass, or taking a sash or frame out — those are not DIY jobs. Do not block trickle vents permanently, do not seal a room airtight to ‘keep the heat in’, and do not paint over or cover a large area of visible mould and call it fixed. Do not force a window handle that will not turn, and do not lean out of an upstairs window to reach hinges. If water is pooling on sills or soaking plaster, if condensation runs down walls rather than just glass, or if a frame is cracked or warped, stop — that is beyond these guides.
How diagnosis works on this page
Window faults are expensive to guess at, because the wrong guess is usually a whole new window. The two guides here share one rule: locate the problem exactly first, then fix only that thing.
- Name the symptom exactly. Is the water inside the glass, between the panes, or outside? Is the draught at the sash edge, the hinge side, one corner, or between the frame and the wall?
- Run the confirming test. The location check for condensation, and the back-of-the-hand plus paper-grip test for draughts. Both are free, take minutes, and decide the fix.
- Fix in order. Ventilation and heat before glass for condensation; cam adjustment before seals for draughts — cheapest and most likely first, with the ‘if that didn’t fix it’ cause already written into the same guide.
Symptom → likely cause: the damp-and-windows overview table
| What you notice | Most likely cause | Where to start |
|---|---|---|
| Streaming windows every morning, water wipes off the inside glass | Overnight moisture + cold glass — breathing, shut vents, a cold room | Condensation guide — morning routine |
| Condensation only in one bedroom, not others | That room is colder, damper, or worse ventilated — north-facing, unheated, or door kept shut | Condensation guide — room-by-room table |
| Windows clear in the morning but wet by evening | Daytime moisture load — cooking, showers, or clothes drying | Condensation guide — drying and extractor rules |
| Misty, streaked glass you cannot wipe, between the panes | Failed sealed unit — moisture trapped inside the glazing; replacement by a glazier, not ventilation or adjustment | Condensation guide — ‘When it IS the window’ |
| Condensation on the outside in the morning, clearing by mid-morning | Good glazing doing its job — outer pane cold, inner pane warm; no action needed | No guide needed — this is not a fault |
| Cold air all around the sash edge, handle closes easily | Loose locking cams — sash not compressing against the seal | Draughty uPVC guide — cam adjustment |
| Draught strongest on the lock/handle side | Cams on the lock side out of adjustment — uneven compression | Draughty uPVC guide — adjust evenly, quarter-turn at a time |
| Draught on the hinge side, or the sash looks slightly out of square | Worn or loose hinges (friction stays) — sash not sitting square | Draughty uPVC guide — hinge section |
| Draught from between the frame and the wall, not the sash edge | Perimeter sealing problem — old mastic or a frame-to-wall gap; a different fix | Draughty uPVC guide — diagnosis section |
| Water pooling on the sill, paint peeling, or plaster damp | Sustained moisture, not a morning mist — ventilation plus a possible leak or cold bridge; professional look | Beyond these guides — see ‘When damp and windows are NOT a DIY job’ below |
Two honest notes on the table. First, condensation and draughts often arrive together in winter, but they are different faults with different fixes — ventilating a draughty window will not tighten its cams, and adjusting cams will not dry a damp room. Second, a problem that is getting worse week by week, or that appeared suddenly after building work, a leak, or a new heating system, outranks both guides: get it looked at rather than living with it through the winter.
Start with your symptom — the damp-and-windows guides
Windows that stream every morning
Condensation on Bedroom Windows Every Morning? The Routine That Actually Stops It (UK)
Start here if: your bedroom windows stream every morning in the cold months and the water wipes off the inside glass. The guide opens with the one check that splits this fault in three — inside the glass means room moisture, between the panes means the sealed unit has failed, outside the glass means the glazing is working well — then gives the whole fix for the common case: trickle vents open, a 10-minute morning purge with the bedroom door cracked, steady background heat, plus the drying-clothes and extractor rules that stop the moisture building up in the first place. It also covers when a dehumidifier is actually worth it, and when the window itself is the problem. Cost: £0 for the routine; £0–£150+ only if you add kit.
Windows that let cold air in
Draughty uPVC Window? Adjust the Locking Cams Before You Pay for New Seals (UK)
Start here if: you feel cold air at the edge of a closed, locked uPVC window. The guide starts with the walk-around diagnosis — back of the hand around the sash edge, then the paper-grip test — so you know whether the air is coming from loose cams, worn hinges, a dropped sash, or the frame-to-wall gap. For the common case it walks the fix step by step: mark each cam, adjust a quarter-turn at a time and evenly around the sash with a 4 mm Allen key, re-test with paper, and lubricate lightly. Seals come last, not first: only a gasket that is perished, torn, hardened, or permanently flattened gets replaced, and its profile must be matched by sample. Cost: £0 for the adjustments; £5–£30 only if seals are needed.
The two tests that decide most of these faults
The location check (condensation, 1 minute). Look at the glass in the morning before you wipe anything. Inside the glass, and you can wipe it off, means room moisture — follow the routine. Between the panes, and you cannot wipe it, means a failed sealed unit — no ventilation or adjustment fixes it, and a glazier replaces the unit. Outside the glass means the glazing is keeping heat inside — do nothing.
The paper-grip test (draughts, 2 minutes). Close and lock the window with a sheet of paper trapped at several points around the sash edge, and try to pull it out at each point. Where it slides out easily, that spot is not compressing; where it grips, the seal there is fine. Do it before you adjust anything, so you know which cams to move — and repeat it after, so you know when to stop. A handle that gets stiff means you have over-tightened: back every cam off a quarter-turn.
When damp and windows are NOT a DIY job
Diagnosis is nearly always safe; some situations are not a learning opportunity. Stop and get professional advice, or raise it with your landlord in writing if you rent, if:
- Water is pooling on sills, soaking plaster, or running down walls rather than just glass. That is sustained moisture, not a morning mist.
- A large or recurring mould patch is present. Do not paint over it and call it fixed — the moisture cause is still there.
- The sealed unit has failed (mist between the panes). A replacement unit is a glazier’s job, not a DIY one.
- The sash has dropped badly, a hinge is bent or broken, or hinge screws spin without gripping. Adjusting cams will not square it, and forcing the handle can break the lock.
- The frame is cracked, warped, or the frame-to-wall gap is large. That is a perimeter or frame repair, not a sash adjustment.
- The problem appeared suddenly after building work, a leak, or a new heating system. A new cause needs a proper look, not a routine.
US / UK term box
| US term | UK term used in these guides |
|---|---|
| Window vent / slot vent | Trickle vent |
| Exhaust fan | Extractor fan |
| Double-pane window | Double glazing / sealed unit |
| Draft | Draught |
| Vinyl window | uPVC window |
| Hex key | Allen key |
| Hinge / friction hinge | Friction stay |
| Striker plate | Keep |
| Weatherstrip / weatherstripping | Gasket / draught seal |
| Glazier | Glazier (same) |
| Radiator / baseboard heater | Radiator |
FAQs
My windows are wet every morning — do I need new windows?
Only if the water is between the panes, where you cannot wipe it. Water on the inside of the glass means room moisture meeting a cold surface — a ventilation and heating issue, not a failed window. The condensation guide walks the 10-minute routine that fixes the common case for £0.
Will adjusting the cams fix every draughty uPVC window?
No — it fixes the common case, loose cams letting the sash sit slack against the seal. It will not fix a dropped sash, a broken hinge, a frame-to-wall gap, or a failed sealed unit. That is why the draughty-window guide starts with diagnosis: find where the air is coming from, then fix that thing.
I have both problems — condensation and a draught. Which do I fix first?
Diagnose both separately, because they are different faults. Run the location check for the condensation and the paper-grip test for the draught, then fix each in its own guide’s order: routine first for condensation, cam adjustment first for the draught. Do not assume fixing one will fix the other.
The condensation started after I got new windows. Did they fit them wrong?
Probably not — new, well-sealed windows stop the accidental draught ventilation the old windows provided, so the room is now more airtight and needs its trickle vents open and the morning purge more, not less. If a new unit itself is misty between the panes, that is a different matter — a failed unit, and the installer should replace it.
Do I need new seals, or just an adjustment?
Adjustment first, always. Only replace a seal that is perished, torn, hardened, or permanently flattened — and match its profile with a sample before buying. A dirty or slightly compressed seal is not a failed seal; clean it, adjust the cams, and re-test.
How often should I check my windows?
Once a year, at the start of autumn before the cold winds arrive, covers both checks: vents open and the morning routine ready, plus a quick paper-grip test on any window that feels draughty. A drop of silicone or PTFE lubricant on the cams at the same visit keeps them moving freely.
FaultToFix damp-and-windows guides are written symptom-first: diagnosis before fix, cheapest check first, and a clear line where DIY stops. Browse all guides in this cluster in the Damp & Windows archive.
Last updated: 28 October 2026