Fix It Britain

Knowing how to clean uPVC windows and frames properly does far more than make them look nice. Grit left in the frame scratches the surface, blocked drainage slots let rainwater sit in the bottom of the frame, and dry hinges are the main reason windows start to stick and catch. Autumn is the ideal time to do it: you clear out the summer’s dust and the first fallen leaves before winter rain, condensation and frost set in.

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At a glance

• Difficulty: Easy – no special skills, just patience and the right (gentle) products
• Time needed: 15–25 minutes per window for a full clean of frame, seals, drainage slots and glass; a quick wipe-over takes about 5 minutes
• Best time to do it: A dry, overcast day in autumn and again in spring – direct sun dries soapy water too fast and leaves smears
• Best for: White, coloured and woodgrain-foiled uPVC casement, tilt-and-turn and sliding sash windows, plus uPVC doors

Know what you’ve got before you start

Most double glazing fitted in UK homes since the 1980s is uPVC (also written PVCu or PVC-U), but not all of it is the same, and the finish matters more than anything when you choose what to clean it with.

Smooth white uPVC is the most common and the most forgiving. It has a slightly glossy surface that dirt sits on top of rather than sinks into, so warm soapy water shifts almost everything.

Foiled uPVC – the anthracite grey, black, cream and woodgrain-effect frames that have become popular – has a thin laminated film over the plastic. This is the one to be careful with. REHAU, one of the big profile manufacturers, warns in its care guide that solvent- or thinner-based cleaners and polishes can discolour both foiled and white frames and weaken the surface. On a foiled frame that damage can’t be polished back out.

The parts that aren’t uPVC need thinking about separately: the rubber gaskets (usually black or grey) that seal the glass and the opening sash, the metal hinges and locking gear hidden in the edge of the sash, and the glass itself. Each needs a slightly different approach, which is why this guide works through them in order.

When cleaning isn’t enough

Cleaning won’t fix everything. If the glass is misted between the panes, the sealed unit has failed and needs replacing. If the rubber gaskets have shrunk away from the corners, cracked or gone hard, they need renewing. According to Designing Buildings Wiki, older EPDM-type seals may last around 10 years, or as little as five depending on quality and exposure, and seals should be checked annually. And if a window is dropping, scraping or hard to lock even after cleaning and oiling, the hinges may need adjusting or replacing.

What you’ll need

• A bucket of warm water with a squirt of mild washing-up liquid
• Two or three soft microfibre cloths (one for washing, one for rinsing, one for drying)
• A non-abrasive sponge
• A soft brush, a small paintbrush or an old toothbrush
• A vacuum cleaner with a crevice or brush nozzle
• A non-abrasive uPVC cleaner for stubborn marks (optional)
• White vinegar (optional, for light mould spots)
• A squeegee and window washer applicator for the glass
• Light machine oil such as a 3-in-1 multi-purpose oil, for hinges and locking gear
• Rubber gloves
• A sturdy step stool, or an extension pole for windows you can’t reach safely

Step 1: Clear loose dirt and debris first

Open the window fully and look at the frame rebate – the recessed channel the sash closes into. Dead flies, cobwebs, dust and leaf litter collect here, and it’s usually much dirtier than the face of the frame.

Vacuum it out with a crevice or brush nozzle before any water goes on. Then go along the corners and hinge areas with a soft brush. This step matters because grit is what scratches uPVC: wipe a wet cloth over a gritty frame and you’re effectively using fine sandpaper. REHAU’s care guide makes the same point – remove grit before cleaning, as debris can scratch the surface.

Step 2: Wash the frames with warm soapy water

Mix a small squirt of washing-up liquid into a bucket of warm (not hot) water. Wring out a microfibre cloth or soft sponge so it’s damp rather than dripping, and wipe the frames from the top down so dirty water runs onto areas you haven’t cleaned yet, not ones you have.

Cover the outer frame, the sash, the rebate and the sash edges you only see when the window is open, rinsing the cloth often. Then go over each section with a second cloth in clean water to lift soap film, and dry it with a third. Skipping the drying is why frames end up dull and streaky.

For marks that soapy water won’t shift – black scuffs, sticky residue, traffic film on frames facing a busy road – use a non-abrasive cleaner made for uPVC. Spray or apply it to the cloth rather than the frame, rub gently, then rinse and dry. Always test anything new on a hidden spot first, such as the underside of the sill, especially on foiled frames.

A note on “cream cleaners”

Specialist uPVC cream cleaners are made for window frames, but ordinary household cream cleaners for hobs and baths contain fine abrasives. Cleanipedia lists cream cleaners alongside scouring pads and iron wool as things to avoid, because they wear away the glossy finish. Check the label says it’s suitable for uPVC.

Step 3: Clean the rubber seals and gaskets

The rubber gaskets around the glass and sash are often where you’ll find black mould spots, especially on north-facing windows and in bathrooms and bedrooms that get a lot of condensation.

Wipe them with a cloth dampened in the same mild soapy water. Don’t drag hard along the edge – gaskets sit in a groove and can be pulled out of place. For light mould spots, Homebuilding & Renovating suggests warm soapy water with a splash of white vinegar, but notes that vinegar should be diluted and not left sitting on sealant for long, as it can break it down. Rinse afterwards.

Avoid neat bleach. In the same article, a glazing specialist warns that bleach can permanently discolour or dull uPVC, make it brittle and weaken rubber and silicone seals. If mould has got into the silicone bead around the outside of the frame rather than just sitting on the surface, cleaning won’t remove it; the bead needs cutting out and replacing.

If mould keeps coming back, the real problem is moisture – keep trickle vents open and see our condensation guide linked below.

Step 4: Clear the drainage slots

Look along the bottom of the outer frame, on the outside face and inside the rebate. You’ll see small slots or holes, sometimes behind little plastic hooded covers. These are drainage slots, and they’re designed to let any rainwater that gets past the outer seal drain back outside.

When they block with dirt, dead insects or leaf debris, water pools in the bottom of the frame. That can lead to water seeping indoors onto the sill, and in cold weather the trapped water can freeze. REHAU’s guide says to keep drainage slots and channels clear of blockages.

Vacuum the rebate along the bottom track, then poke gently through each slot with a pipe cleaner, a small brush or a straightened cable tie. Don’t use a screwdriver or anything sharp that could split the plastic. To check they’re clear, pour a little water slowly into the bottom of the rebate with the window open; it should drain away steadily rather than sitting in the channel.

Step 5: Clean and lubricate the hinges and locking gear

With the window open, brush out the friction hinges at the top and bottom of the sash and the locking strip along the opening edge. Wipe them with a damp cloth and dry them.

Then lubricate the moving parts. REHAU recommends a non-acidic mineral oil, such as 3-in-1 multi-purpose oil, on the pivot points of locks and hinges at least twice a year. One drop on each pivot and on the mushroom-shaped locking cams is plenty. Open and close the window a few times and work the handle to spread it, then wipe off any excess so it doesn’t attract dirt.

For uPVC door lock cylinders, REHAU suggests a little PTFE-based lubricant on the key, turned in the lock a few times. Keep WD-40 and similar solvent sprays off the frames; Cleanipedia and Homebuilding & Renovating both list it among products to avoid on uPVC.

If your windows have child-safety restrictors, Designing Buildings Wiki suggests releasing them so you can reach the runners and hinges, then making sure the restrictor is engaged again afterwards. Don’t forget this last bit.

Step 6: Clean the glass

Do the glass last, so drips from the frames don’t spoil it. REHAU’s advice is to wash it with warm soapy water, dry it, then use a household glass cleaner and a clean cloth. A squeegee, worked from top to bottom, helps prevent streaks and drips. Take off rings and watches first, as they can scratch the glass.

For the best finish, wet the glass with a washer applicator, then pull the squeegee across in overlapping strokes, wiping the blade on a dry cloth after every stroke. Finish the edges with a dry microfibre cloth. Try to keep glass cleaner off the frames; Homebuilding & Renovating lists glass cleaner among the products that can damage uPVC surfaces.

Upstairs windows: don’t lean out of open windows or stand on a chair to reach. Many casement windows have “easy clean” hinges that let the sash swing far enough to reach the outer pane from inside. Otherwise, use a telescopic pole from the ground, or leave upper floors to a window cleaner.

Step 7: Check everything closes and seals properly

Close each window and check it shuts smoothly and the handle locks without forcing. Look at the gaskets to make sure none have been pulled out of their groove. A quick draught test: close the window on a sheet of paper. If the paper slides out easily at any point, the seal there isn’t making good contact, and our draught-proofing guide explains the next steps.

Twice a year – autumn and spring – is a sensible routine, with extra quick wipes for windows facing a busy road.

Common mistakes to avoid

• Using a pressure washer or steam cleaner. REHAU specifically warns against both. They can force water past seals and heat can damage the surface.
• Using abrasive pads, scouring powder or household cream cleaners. They wear away the glossy finish, leaving frames duller and easier to stain in future.
• Reaching for solvents. White spirit, nail varnish remover, thinners and similar products can discolour uPVC permanently, and the damage is worse on foiled frames.
• Using neat bleach on mould. It can dull frames and weaken the rubber seals you’re trying to clean.
• Wiping before vacuuming. Wet grit scratches. Always remove loose dirt first.
• Cleaning in bright sunshine. Water dries too quickly and leaves streaks on both frames and glass.
• Forgetting the drainage slots and hinges. These are the parts that actually affect how well your windows work.

When to call a professional

Call a window repair specialist or your original installer if you notice condensation between the panes (a failed sealed unit), a sash that has dropped and catches on the frame even after lubricating, a handle or lock that won’t engage, cracked or split frames, or gaskets that are shrunken or missing. If your windows are still under guarantee, check before doing any repairs yourself, as some guarantees require the installer to do the work. Some installers can also refurbish faded or yellowed frames that cleaning won’t bring back.

Frequently asked questions

What is the best thing to clean uPVC window frames with?

Warm water with a little mild washing-up liquid and a soft cloth handles most dirt. For stubborn marks, use a non-abrasive cleaner labelled as suitable for uPVC, and test it on a hidden area first. Rinse and dry the frame afterwards so you don’t leave a film.

Can I use bleach on uPVC windows?

It’s best avoided, especially undiluted. Glazing specialists warn that bleach can discolour or dull uPVC and weaken the rubber seals. Use soapy water, a little diluted white vinegar, or a mould remover that says it’s safe for uPVC and seals.

How do you get yellowed uPVC white again?

First give the frame a thorough clean, because much of what looks like yellowing is a layer of grime. If it’s still discoloured, a specialist uPVC restorer may help. If the plastic itself has yellowed through age and sunlight, cleaning won’t reverse it fully; frames can be professionally resprayed or, in some cases, the window replaced.

How often should I clean my uPVC windows?

Wipe the frames every few months and do a full clean, including drainage slots and lubricating hinges, twice a year. REHAU recommends lubricating moving parts at least twice a year. Windows near busy roads, trees or the coast benefit from more frequent attention.

Is WD-40 OK on uPVC window hinges?

Several UK guides advise keeping WD-40 off uPVC frames. For hinges and locking points, a light non-acidic machine oil such as 3-in-1 is what window profile manufacturers like REHAU recommend. Apply a drop to each pivot and wipe off the excess.

Related guides: How to Stop Condensation on Windows · How to Draught-Proof Doors and Windows · How to Clear and Fix a Leaking Gutter