Most uPVC window problems, such as draughts, a sash that drops or scrapes, or a handle that won’t lock, can be fixed with small adjustments to the locking cams, keeps or hinges. You’ll usually need just an Allen key and a screwdriver. This guide shows you how, and how to tell when it’s time to replace your windows instead.
Signs Your uPVC Windows Need Adjusting
- Draughts around the frame when the window is closed
- The window scrapes or sticks when opening
- The handle is stiff or won’t lock smoothly
- Uneven gaps between the sash and the frame
- The window rattles in the wind
Adjusting early prevents strain on the hinges and damage to the seals.
Tools You’ll Need
| Tool | Used for |
|---|---|
| Allen keys (usually 4mm or 5mm) | Locking cams and hinge adjustments |
| Screwdrivers (Phillips and flathead) | Keeps and hinge screws |
| Pliers | Turning locking cams on some windows |
| Spirit level | Checking the sash sits level |
| Light machine oil or silicone spray | Lubricating hinges and locks |
Safety tip: support the weight of the sash while you work on the hinges, especially on large or upstairs windows.
Step 1: Stop Draughts by Adjusting the Locking Cams
Most uPVC windows have locking cams along the opening edge of the sash. When you turn the handle, these cams slide into the keeps on the frame and pull the window tight against the seals.
- Open the window and find the cams on the edge of the sash.
- Turn each cam slightly with an Allen key or pliers to increase compression, which pulls the window tighter.
- Close the window and check for draughts.
- Don’t over-tighten. If the handle becomes very stiff, ease the cams back slightly.
If draughts continue, check the rubber seals for cracks or gaps. Clean them with warm soapy water and replace any damaged sections. For more fixes, see our 6 steps to stop draughts.
Step 2: Fix a Window That Won’t Lock
If the handle won’t turn fully, the cams probably aren’t lining up with the keeps on the frame.
- Close the window slowly and watch where the cams meet the keeps.
- Loosen the screws on any misaligned keep, move it slightly into line, and retighten.
- Test the handle. It should lock smoothly without forcing.
If the window has dropped, fix that first (Step 3), because a dropped sash is the most common cause of misaligned locks.
Step 3: Fix a Dropped or Scraping Window
A dropped sash sits lower on the handle side, leaves an uneven gap at the top, and may scrape the frame when closing.
- Open the window and check the hinges at the top and bottom for loose screws. Tighten any that are loose.
- Some hinges have an adjustment point on the sliding part of the hinge that lets you move the sash slightly. Adjust it in small steps.
- Close the window and check that the gaps around the sash are even.
If tightening doesn’t fix it, the hinges may be worn or the glass may need re-packing. A window repair specialist can do this, but if your windows are older or have several problems, replacing them is often the better long-term option.
Step 4: Fix a Stiff Window
- Clean dirt and debris from the hinges, cams and locking mechanism.
- Apply a little light machine oil or silicone spray to the moving parts.
- Open and close the window several times to spread the lubricant.
- Keep oil off the rubber seals.
Step 5: Stop a Window Opening Too Far
Friction hinges add resistance, but they aren’t designed to limit how far a window opens. If you need to limit the opening, especially on upstairs windows or in homes with children, fit window restrictors.
If your window has egress (fire escape) hinges, don’t restrict them permanently. They must open fully so you can escape in an emergency. Choose restrictors with a release catch that adults can open quickly.
Step 6: Adjust Tilt & Turn Windows
Tilt & turn windows have a different mechanism from casement windows:
- Height: usually adjusted with an Allen key at the bottom corner hinge.
- Side-to-side position: adjusted at the bottom hinge and the top stay arm.
- Compression (draughts): adjusted by turning the locking cams around the sash, as in Step 1.
- Test both the tilt and turn positions after each small adjustment.
Adjustment points vary between systems. If you’re unsure, check the manufacturer’s instructions before adjusting. See our tilt & turn windows.
DIY or Repair Specialist?
| Job | DIY | Repair specialist |
|---|---|---|
| Adjusting locking cams | ✅ | |
| Realigning keeps | ✅ | |
| Tightening hinge screws | ✅ | |
| Lubricating hinges and locks | ✅ | |
| Replacing seals | ⚠️ Possible | ✅ Recommended |
| Replacing worn hinges | ✅ | |
| Re-packing glass in a dropped sash | ✅ | |
| Broken locking mechanism | ✅ |
When Is It Time to Replace Your Windows?
If adjustments no longer work, it may be time for new windows. Signs include:
- Condensation between the panes, which means the sealed unit has failed
- Warped frames, or sashes that won’t close even after adjusting
- Rain getting in around the frame
- Single glazing
If you’re adjusting the same windows again and again, replacement usually costs less in the long run than repeated repairs. Learn what to look for in our guide to the most energy efficient windows.
FAQs
What size Allen key do I need to adjust uPVC windows?
Usually 4mm or 5mm, depending on the hinge and lock design.
How do I adjust a uPVC window that has dropped?
Tighten any loose hinge screws, then adjust the hinge in small steps if it has an adjustment point. If the sash still drops, the hinges may need replacing or the glass re-packing.
How do I stop draughts from a uPVC window?
Turn the locking cams to pull the sash tighter against the seals, then check the seals for damage.
Why won’t my uPVC window lock?
The cams and keeps are usually misaligned, often because the sash has dropped. Realign the keeps, or fix the drop first.
Can I lubricate uPVC window hinges?
Yes. Use light machine oil or silicone spray on the hinges and locks, and keep it off the rubber seals.
Time for New Windows?
If your windows no longer respond to adjustment, it may be time to replace them. Trade uPVC Windows is a family-run company that has supplied and installed A-rated uPVC windows across Glasgow and the Central Belt since 2013. We’ll measure for free and give you a no-obligation quote.
