How To Adjust Double Glazed Windows

Fixing window hinge

Of all the home improvement options on the market, double-glazed windows continue to be one of the most valued. With their ability to both keep heat in the home and prevent noise coming from outside, they are considered well worth the investment.

Unfortunately, like all components of your home, double glazing (or triple glazing for that matter) is prone to wear and tear over time, as well as a host of other issues that may result in it being misaligned. Misalignment of your double glazing reduces its efficiency across the board and must be rectified as soon as possible. But how? Ultraseal has put together this guide to outline the DIY window adjustment process.

How do I know when to adjust UPVC Windows? 

There are tell-tale signs that can tell you when an uPVC window unit is misaligned and requires adjustment. They consist of the following: 

  • Difficulty opening/closing – If you cannot open or shut your uPVC windows smoothly, then something is interfering with its intended function. If your window sticks, this could be due to a misalignment of the sash. 
  • Visible gaps – If you can see a gap between the sash and the uPVC window frame, then this is a clear sign that your windows need adjustment. These gaps allow heat transfer to completely bypass your windows, making your double glazing ineffective. 
  • Draughts – Air can enter your home through your uPVC windows despite them being shut due to a draught. If your seals and window panes are undamaged, the most likely cause of this is a misalignment. Don’t ever ignore a draughty upvc window.

Double-glazed windows – The components 

Here is a quick explanation of the window frame and all its parts for understanding:

  • UPVC Frame – The frame is the outermost part of the uPVC windows, and is a structural boundary that not only holds the entire uPVC window in place but anchors it to the wall. It can be made of various materials, such as wood, aluminium, uPVC etc. 
  • Window Sash – The window sash is a component inside the frame that allows the sliding motion that opens/shuts your windows. 
  • Seals – Seals are strips of rubber/silicone pressed into the grooves of the uPVC windows perimeter, encircling it entirely. These are vital to ensure the insulation properties of your window are in effect. 
  • Glazing – The glazing refers to the glass itself. They consist of multiple glass panes spaced apart, with insulating argon gas filling the gap between them. This is essential for insulation. 

What tools do I need to adjust my UPVC Windows? 

Before we go into the step-by-step guide, here are the tools you’ll require to adjust UPVC windows. 

  • Screwdriver – Flathead and Phillips head screwdrivers are required for the majority of adjustments. 
  • Silicone lubricant spray – Lubrication allows the moveable window panel(s) to move without grinding.
  • Small pry bar/putty knife – Useful for removing trim/moulding around the window frames. 
  • Caulking gun/waterproof sealant – Fill in any gaps or cracks to ensure a secure fit. 
  • Measuring tape – This allows you to accurately measure and align windows during adjustment processes. 
  • Flashlight – Flashlights help identify gaps and cracks in window frames/seals. 
  • Silicone-based sealant – To fill any gaps found. 
  • New weatherstripping – Only necessary if the old one is worn out/damaged, to ensure tight seals. 

Step-by-step guide to adjusting double-glazed windows

The following are the five major steps to adjusting your upvc windows. 

Adjusting the hinges for vertical alignment

  1. Identify the hinge – Identify whether your hinge is a butt hinge or a Flag Hinge. 
    1. Butt hinge – A butt hinge consists of two plates connected by a pin, mounted on the edge of the door and frame. 
    2. Flag hinge – A flag hinge is mounted on the surface and takes on the shape of a flag. 
  2. Loosen the hinge screws – Find the window casement left and right side hinge screws that hold the metal strip down and loosen them. 
  3. Adjust for vertical alignment – A flag hinge will require an Allen key to turn the adjustment screw. Butt hinges require manual lifting. 
  4. Retighten screws – When you’re satisfied with the alignment of your uPVC window, tighten the screws afterwards. 

Adjusting the locking mechanism for a tighter seal 

  1. Locate the locking mechanism – The locking mechanism is on the side of the window sash, meaning you need to open up your window completely to gain access. 
  2. Adjust the locking points – Use a screwdriver/Allen key to adjust the cams/locking points. You can control how tightly the window seals are when closed this way. 
  3. Test the adjustment – Close the window. If it closes smoothly without excessive force and leaves no visible gaps, then the job is done. 

Balancing the sash for smooth operation

  1. Check sash alignment – Make sure that the sash is positioned evenly within the uPVC window frame. 
  2. Adjust – Use the hinge to adjust, slightly raising or lowering either side of the sash and look for a balanced position for your uPVC windows.
  3. Lubricate moving parts – Reduce the friction of your window by applying silicone lubricant to the hinges and sliding tracks. 

Seal inspection and adjustment

  1. Inspect seals – Look for signs of damage on your uPVC window, including wear and tear or gaps. 
  2. Replace if necessary – Self-explanatory. Remove and reseal them carefully, ensuring they sit properly in the grooves. 


  1. Check adjustments – Open and close the window properly several times in a row, and ensure that the window functions smoothly.
  2. Inspect for Gaps – Look for gaps visually and feel around the seals to find if there are any draughts. 
  3. Full Lubrication – Apply a final coat of silicone lubricant on all moving parts. This will ensure ongoing smooth operation and protect against wear


Overall, your windows are responsible for both security and the comfort of your home. It’s important to keep them working in top condition and addressing any issues early on. Remember, if there is a fault, it will only get worse over time so it is better tackled when it first occurs, so ensure you adjust uPVC windows when they become misaligned. 

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