How to  Measure a Window Frame Accurately

When replacing a window frame, accuracy in your measurements is key. Whether you’re upgrading to double glazed units, replacing an old UPVC window frame, or switching to a timber window frame, getting the measurements right from the start will ensure the new window fits properly, functions well, and lasts for years to come.

This detailed guide walks you through the essential steps for measuring a window frame for replacement windows, ensuring precision every time.

We’ll cover everything from traditional wooden window frames to modern aluminium window frames and UPVC window frames. So, let’s dive into the specifics, starting from the basics.

Why Accurate Measurements Matter

The key to getting a well-fitting window frame lies in precise measurements. Without accurate measurements, your new window might not fit correctly, leading to unnecessary costs for reordering or adjustments.

Whether you’re replacing old wooden window frames, installing a metal window frame, or upgrading to a modern aluminium window frame, the measurements you take will impact the overall quality and efficiency of your window installation.

General Guidelines for Measuring Window Frames

Before getting into the specifics of each type of window, here are some key general guidelines you must follow to ensure accurate measurements:

1. Measure the Brick Opening, Not the Existing Frame
   Always measure the opening in the wall (brick-to-brick), not the old window frame or door. This will provide you with the most accurate dimensions to fit your new window frame.
   
2. Measure in Multiple Places
   To account for any irregularities in your wall or frame, measure in at least three different spots (top, middle, and bottom for width; left, middle, and right for height). Always use the smallest measurement to ensure your new frame fits snugly.
   
3. Deduct 10mm
   For an accurate fit, always deduct 10mm from both the width and height measurements to allow for a 5mm fitting allowance around the new frame. This ensures the new frame sits plumb and square.
   
4. Supply Measurements in Metric
   All dimensions should be provided in metric units (millimeters), and when measuring, always view the dimensions externally (the outside of the frame).
   
5. Professional Help is Recommended
   If you’re unsure about your measurements, consider consulting a professional fitter, joiner, or builder to get accurate results. At Glazion Home Solutions, we’re happy to assist you with any measuring questions you might have.
   

Step 1: Measure the Width of Your Window Frame

To begin, you’ll need to measure the width of your window frame. Here’s how:

1. Measure at the top of the window frame: Use a tape measure and measure from one side of the frame to the other. Take note of the measurement.
   
2. Measure at the middle: Next, measure the window frame width in the middle of the frame.
   
3. Measure at the bottom: Finally, measure at the bottom of the frame. This will help you identify if the window frame is square or if there is any bowing.
   

If your measurements vary slightly from top to bottom, be sure to take the smallest width as your final measurement. This ensures the new window frame will fit without issues.

Step 2: Measure the Height of the Window Frame

Now that you have the width, it’s time to measure the height:

1. Measure from the top of the window frame to the sill (the bottom part of the frame).
   
2. Take multiple measurements: Measure the height on the left side, right side, and in the middle to ensure the window frame is vertical and square.

If you find that the height measurements differ slightly, use the smallest height to ensure the new window frame will fit without gaps or excess space.

Step 3: Measure the Depth or Thickness of the Window Frame

To replace your window frame correctly, you need to measure the depth or thickness of the frame as well. This is especially important when dealing with double glazed units, as the frame must be deep enough to accommodate the replacement double glazed units.

1. Measure from the inside of the frame to the outside of the frame, checking the depth along both the sides and the middle of the frame.
   
2. If you’re replacing an aluminium window frame, UPVC window frame, or timber window frame, take note of any additional features, such as insulation or trim, which may affect the measurement.
   

When measuring the thickness of double glazed units, be sure to measure the overall thickness, including the glass panes and the spacer bars that separate them. This will ensure your replacement double glazed units fit perfectly within the frame.

Measuring for Specific Window Types

How to Measure a Double Glazed Window Frame

If you’re replacing double-glazed windows, here’s how to take the correct measurements for the window frame:

Step 1: Measure the Width

• Measure from brick-to-brick at three points: the top, middle, and bottom of the opening.
  
• Use the smallest measurement for the width.
  
• Deduct 10mm from the final width measurement to allow space for fitting.
  

Step 2: Measure the Height

• Measure from brick-to-brick at three points: left, middle, and right of the opening.
  
• Use the smallest measurement for the height.
  
• Deduct 10mm from the final height measurement to allow fitting space.
  

These steps apply to all standard windows, including those with UPVC, aluminium, or timber frames.

How to Measure for a Double Glazed Door Frame

For those replacing double glazed doors, the process is slightly different, as you need to account for the door panel and its surrounding frame.

Step 1: Measure the Width

• Measure from brick-to-brick at three points: top, middle, and bottom of the opening.
  
• Use the smallest measurement for the width.
  
• Deduct 10mm from the final width to accommodate fitting allowances.

Step 2: Measure the Height

• Measure from brick-to-brick at three points: left, middle, and right of the opening.
  
• Use the smallest measurement for the height.
  
• Deduct 10mm from the final height to ensure proper fit.

How to Measure for a Window with Side Panels or Top Light

Windows with additional features such as side panels or top lights require special attention to detail. Here’s how to measure for these types:

Side Panels

• Width: Measure from brick-to-brick at three points along the opening (top, middle, and bottom). Use the smallest measurement and deduct 10mm.
  
• For the side panel width, measure from the center of the frame between the door and the panel, to the outer edge of the panel frame.

Top Light

• Height: Measure from brick-to-brick at three points (left, middle, and right). Use the smallest measurement and deduct 10mm.
  
• Depth: Measure from the center point of the frame (between the door and top light) to the top of the door frame to get the transom drop for the top light.

How to Measure a Square Bay or Angled Bow Window

Bay and bow windows require more complex measurements due to their shape and the angles involved.

Square Bay Window

• Back Span (Width): Measure from the existing frame edge to edge internally. Ensure both side windows are measured for consistency.
  
• Height: Measure externally, brick-to-brick, including any existing sill.
  
• Add 140mm for the two 90-degree corner posts that are 70mm square each.
  

Bow Window

• Back Span (Width): Measure from the existing frame edge to edge internally for each individual window facet.
  
• Projection: Measure the internal projection from the back span to the inner point of the window frame.
  
• Height: Measure externally, brick-to-brick, including any existing sill.
  

Additional Measurements for Installation

When installing a new door or new windows, you might also need to consider the following:

• Frame squareness: Check the square of the window frame using a carpenter’s square to ensure the window will fit correctly.
  
• Window Hinges: Measure for window hinges if your window will be a hinged model. The location of the hinges will impact the fit of the window.
  
• Window Handles: If you’re replacing handles, measure for the UPVC window handle or any other hardware you plan to install.
  

You may also need to consider the type of plastic door panel if you are replacing your entry door. Ensure you measure the door size and the door frame accurately, including for specific designs like French doors or bifold doors.

Final Measurements and Ordering

Once you’ve taken all your measurements, it’s time to double-check everything to ensure they are accurate. Don’t forget to account for any trim or weather seals, as these may affect the final fitting. When ordering your new windows or UPVC door panel replacement, make sure to give your supplier the exact measurements for both the window frame and the double glazed units. At Glazion Home Solutions, we offer custom solutions tailored to your specific needs, whether you’re looking for wooden window frames, UPVC window frames, or aluminium window frames.

Why Trust Glazion Home Solutions?

At Glazion Home Solutions, we make the replacement process simple and efficient. We offer a wide range of replacement windows, including double glazed units, UPVC window frames, and timber window frames to meet your needs. Our team of experts is ready to guide you through every step, from measuring to installation.

If you’re ready to replace your window frames or upgrade your door panels UPVC, don’t hesitate to reach out for a free consultation. Let us help you make your home or building more comfortable and energy-efficient.

Conclusion

Accurately measuring your window frame is essential for a successful replacement. By following these simple steps, you’ll ensure that your replacement windows fit perfectly, offering both durability and efficiency. Whether you’re replacing timber window frames, upgrading to double glazed units, or installing aluminium window frames, taking the time to measure your frames properly will save you time and money in the long run.