Video by uPVC Spares 4 Repairs. This guide is based on "How to fix sticking uPVC windows + maintenance tips" from uPVC Spares 4 Repairs, a UK uPVC window and door parts specialist. Their video is particularly good on hinge adjustment — showing exactly which screw does what and in which direction — which makes all the difference if you have never done this before.
1. Work out what is causing the sticking
Before you reach for any tools, open and close the window slowly and watch what happens. Is it sticking at the top, bottom, or side? Does it grind as it swings, or only catch when you try to close it? Does the handle feel stiff?
Different symptoms point to different fixes. A window that drops and scrapes at the bottom is nearly always a hinge issue. One that will not latch is usually the lock mechanism or a misaligned keep. Know the problem before you start.
2. Check and adjust the hinges
Most uPVC casement windows use adjustable butt hinges or flag hinges. Look for an adjustment screw in the centre of the hinge — it is often hidden behind a small plastic cover. A 4 mm Allen key is the tool for most makes.
Turning clockwise typically pulls the sash into the frame; anticlockwise pushes it out. Make small quarter-turn adjustments, close the window, and check the gap around the sash before making another. Work on the top hinge if the bottom of the window drags, and the bottom hinge if the top is catching.
3. Lubricate the hinges and friction stays
Friction stays — the side arms that control how far the window opens — seize up when they dry out. Spray silicone lubricant directly onto the pivot points and slide the stay back and forth a few times to work it in. Do not use WD-40 as a long-term solution; it thins quickly and leaves the metal dry again within a few weeks.
While you are there, apply a light coating to the hinge pivot points too. Wipe off any excess.
4. Lubricate the espagnolette lock mechanism
The multipoint lock running up and down the edge of the sash is called the espagnolette. Over time the shoot bolts — the small metal pins that latch into keeps on the frame — get gummed up with grit and old grease and start sticking.
Spray silicone lubricant into the lock strip along the edge of the sash, then work the handle back and forth several times. You should feel the mechanism loosen up as the lubricant works in. A stiff handle usually means the shoot bolts are binding, not a broken lock.
5. Check that the keeps are aligned
Keeps are the small metal receivers in the frame that the shoot bolts lock into. If the sash has dropped or shifted, the bolt and keep may no longer line up. Open the window and look at each keep in turn. You can usually see a wear mark or scratch where the bolt is meeting the wrong spot.
Some keeps have adjustment screws of their own. Others need to be removed and relocated slightly. If they are too far out of alignment for adjustment, a new set of keeps is a cheap fix — usually under a fiver each.
6. Clean the rubber seals and frame drainage
Dirty, compressed rubber seals make a window feel like it sticks even when the mechanism is fine. Wipe them down with a damp cloth and a small amount of washing-up liquid. Once clean, apply a very light coating of silicone lubricant to the seal to keep it supple and improve the compression.
Also clear the drainage slots at the bottom of the frame — those small holes or channels you see in the outer face of the frame. Blocked drainage causes water pooling, which accelerates seal deterioration and can warp the frame over time.
7. Test the whole operation
Open and close the window ten or twelve times. It should swing freely, latch without force, and lock smoothly. Stand back and check the gap around the sash is even all the way round — about 3–5 mm is normal on a well-aligned casement.
If the window still sticks or drags after all this, the frame or sash may have warped slightly. That is less common in uPVC than in timber but does happen with age and heat exposure.
8. Annual maintenance keeps problems away
Give every window in the house the same treatment once a year — mid-spring is a good time, before summer heat. Hinges lubricated, seals wiped, drainage cleared, locks sprayed. Takes about ten minutes per window and prevents most of the sticking, rattling, and failed locks that otherwise creep up on you.
When to call a handyman
Call Richard if the frame or sash is visibly warped, the glass unit is misted with internal condensation (that is a failed seal unit, not a window adjustment job), or if the hinge is physically broken rather than just stiff. Hinge replacement on a uPVC window is straightforward, but it helps to know the hinge make and size before ordering parts.
Got a window that will not play ball?
The Sandwich Handyman handles uPVC window and door adjustments, hinge replacements, and lock repairs across Sandwich and nearby East Kent villages.
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