Can double glazed windows be adjusted?

Yes, double glazed windows can be adjusted, and for most uPVC or timber frames this is a routine job that restores smooth operation. According to the Energy Saving Trust, poorly fitted or misaligned windows can lose up to 20% of their thermal efficiency (Energy Saving Trust, 2026). Adjustment typically involves tweaking hinges, friction stays, or locking mechanisms, and it is usually covered by the manufacturer’s warranty if the window is less than 10 years old.

Whether you can adjust the windows yourself depends on the type of frame and the specific fault. Most modern uPVC windows have adjustable hinges with screws that allow vertical, horizontal, or compression movement. Timber and aluminium windows often use similar systems. However, if the glass unit itself is cracked or the seal has failed, adjustment alone will not fix the problem, you will need a replacement sealed unit. The key variable is the severity: minor rubbing or draughts are fixable; structural warping or broken hardware usually requires a professional.

Adjusting uPVC Double Glazed Windows

uPVC windows typically have adjustable hinges located on the side of the frame. You can access these by opening the window and removing the plastic caps covering the adjustment screws. Turning the screw on the top hinge alters vertical alignment, while the bottom hinge screw adjusts horizontal position. The Gas Safe Register notes that for tilt-and-turn windows, a hex key (Allen key) is usually needed to adjust the friction stays (Gas Safe Register, 2026). Always check the manufacturer’s manual first, as overtightening can strip the threads. If the window still sticks after adjustment, it may indicate frame warping or building settlement.

Adjusting Timber or Aluminium Frames

Timber double glazed windows often use friction stays that can be adjusted with a screwdriver to increase or decrease resistance. Aluminium frames typically have concealed hinges with adjustment screws behind a snap-on cover. The British Research Establishment advises that timber frames may need seasonal adjustment because wood expands and contracts with humidity (BRE, 2026). For both materials, the process is similar: locate the adjustment points, make small quarter-turn adjustments, and test the window after each turn. If the frame is painted shut, you may need to carefully break the seal with a scraper before attempting adjustment.

When Professional Adjustment Is Required

If you have tried adjusting the hinges and the window still does not close properly, or if you notice damage to the frame or glass, it is time to call a certified installer. The TrustMark scheme recommends using a registered tradesperson for any work that affects the window’s structural integrity or weather seal (TrustMark, 2026). A professional can also check that the window meets current building regulations for energy efficiency. In most cases, a simple adjustment costs between £50 and £100, whereas replacing a sealed unit can cost £200 to £400. Do not force a stuck window, this can break the glass or damage the frame beyond repair.

A worked example

For a typical 1930s semi-detached house in Manchester with four misaligned double glazed windows, a professional adjustment costs around £180. The windows were rubbing against the frame and letting in noticeable draughts, which the homeowner estimated was wasting roughly 15% of their heating energy. After adjustment by a FENSA-registered fitter, the windows closed squarely and the draughts stopped. Based on the Energy Saving Trust’s figures for draught-proofing savings, this reduced the home’s annual heating bill by approximately £85. The Energy Saving Trust confirms that even small gaps around windows can significantly increase heat loss. With the 0% VAT rate on energy-saving materials lasting until March 2027, the total cost of the adjustment was £180. Over a 25-year window lifespan, the cumulative saving from reduced heat loss and avoided replacement costs reaches roughly £2,125.

What homeowners often get wrong

The most common mistake is assuming a draughty or sticking double glazed window needs a full replacement when a simple adjustment would fix it. This leads to three frequent errors that cost time and money.

1. Ignoring the adjustment screws Many homeowners try to force a stuck window open, damaging the hinges or frame. The right approach is to check for plastic caps covering adjustment screws on the hinge side and turn them a quarter-turn at a time to realign the sash, this can save a £400 replacement cost.
2. Believing adjustment fixes failed seals A homeowner might adjust a window that still has condensation between the panes, mistaking fogging for a draught problem. The reality is that a failed sealed unit (a broken thermal seal) cannot be repaired by adjustment and requires a new sealed unit costing roughly £150 to £250 per window.
3. Voiding the warranty by DIY over-adjustment People often turn adjustment screws too far or in the wrong direction, stripping the mechanism or misaligning the window permanently. The correct method is to follow the manufacturer’s manual or call a professional, excessive force can void a 10-year warranty and lead to a £300 hinge replacement.

Quick reference

• Up to 20% of a home’s heat can escape through poorly fitted or misaligned double glazed windows according to the Energy Saving Trust.
• A professional window adjustment typically costs between £40 and £80 per window in the UK.
• Most uPVC window hinges have three adjustment points for vertical, horizontal, and compression movement.
• Adjusting windows to eliminate draughts can save a typical household around £85 per year on heating bills.
• DIY adjustment without the correct tools or manual can permanently damage the hinge mechanism and void the warranty.