What Causes a Window to Be Out of Square?

What Causes a Window to Be Out of Square?

There’s a tremendous amount of math that goes into constructing a home. Ensuring that all elements of the home fit together properly requires careful planning, measurement, and construction. This is no less true when it comes to replacing the windows in your home.

In this article, we’re discussing an issue that can arise from improper window installation: out of square windows (also referred to as: out of parallel, uneven, unlevel, or crooked).

What does it mean when a window frame is out of square?

A square window is one that is level and plumb. To be level, the top and bottom of the window must be exactly parallel to the ground. The sides of a plumb window are exactly perpendicular to the ground.

Using a plum bob and level helps determine proper measurements for a window. If the plumb and level are not accurately used, the window will be out of square.

Many aspects of a window can compromise its function, negatively impacting its energy efficiency, ease of use, and aesthetic. An otherwise high performing window unit can easily become a hole in your pocket if it is not square. After this review, you’ll be able to identify some of the major indicators of out of square windows, pinpoint some of the causes, and remedy the issue.


Out of square or out of plumb windows mean the window frame is crooked and can make it difficult to open the window.

What are signs of an out of square window frame?

Some out of square or crooked windows are very easy to identify. There are cases where one or both sashes are so obviously misaligned with the window jamb that gaps to the outdoors can be seen.

It’s more common, however, for the window to be slightly crooked and not so discernable to the naked eye. Usually, if your windows are out of square, you’ll feel it one way or another.

Here are some of the most common indicators you have crooked windows:

1. Hard to Open

Windows are designed to be easily opened. If you find yourself struggling to crack your windows or are only to able to partially lift the sashes, something is not right. Once you’ve ruled out the possibility of paint, dirt or dust causing the windows to stick it's likely that the window is out of square.

2. Draftiness

Properly installed windows should make your home more energy efficient. Do you walk past your windows and get a chill? If so, you’ve probably got an insulation issue on your hands and it’s doing your home’s HVAC system no favors. An out of square window does not perform optimally, leaving it susceptible to high thermal transfer between outdoor and indoor temperatures. 

3. Leaking

Sometimes when it rains, it pours. However, it should never do so into your home. A leaking window is probably one of the most critical consequences of an out of square window.

The breach between the sash and the frame allows in moisture that can damage not just the frame, but the wall and floor near the window as well. It’s advisable to address any leaking immediately to avoid more serious - and costly - repairs to your walls and floors.  

How can I be certain my window is out of square?

If you suspect that your window is out of square, confirming your suspicion can be pretty simple with a measuring tape. Take a measuring tape and measure the width of the window from jamb to jamb. Check the bottom of the window, the center of the window, and the top of the window. A square window will be the same width at each point that you measure. 

If you need some assistance with measuring you can recruit the help of a friend, relative, or handyman.

If you suspect that you may have bigger problems than just an out of square window you may want to reach out to a local window replacement company to learn what kind of services they provide or if they can lend some advice. 

Windows out of square or windows out of plumb can cause gaps and drafty window units,

What causes an out of square window frame?  

Installation is one of the most common reasons for a crooked or out of square window. The first critical step in the installation process is getting an accurate measurement of the window's rough opening. An accurate measurement ensures that the right windows are ordered for your home or project.

As you go through a replacement window project you should always ask your window consultant or window technician any question that comes to mind with regard to your windows. At the start of your project that may include questions about measurements and ordering and installation processes.

Homeowners that have worked with our company may have noticed that we measure windows and rough openings a few times. The first measurement is usually done during a consultation to provide an estimate for the cost of the windows or project.

Before ordering windows we have one of our window technicians return to the home to get the most accurate measurement of each window opening. Our window technicians measure to within 1/8-inch of the rough opening so that when they install the window it fits properly. 

Once the windows arrive each is measured one last time before the existing windows are removed. Precise measurements make the window installation process run much more smoothly. 

Window installers should be experienced and have good quality tools. Lack of experience or know-how and poor quality tools can also create installation problems that result in out of square windows. For example, if the level or plumb being used is off-kilter you could end up with a window that sits at an angle.

The window frame is screwed to the existing studs, when the window frame is not properly secured, the result can be an out of square window. Sometimes these details can go unnoticed until gravity begins to throw components off track and allows uneven weight distributions to create gaps.

Replacement windows (versus new construction) are manufactured to the exact specifications of your home for the best fit. A properly square window works in harmony with other elements of your home and creates a weathertight seal from the elements.

Out of frame windows or doors can cause loss of home energy efficiency, make windows or doors hard to open and lead to water leakage or fogging.

The damage done by poor measurement and installation can be exacerbated by time. Homes that undergo years of settling can worsen the traits associated with poor measurement and installation. It’s always advisable to correct this issue as soon as it is discovered.  

How do you fix an out of square window frame?

There are a few ways to alleviate the issues caused with out of square windows. This Old House featured an episode showing how to approach a window that is crooked.

Around the two minute mark, contractor Tom Silva removes the wall casing surrounding the window, takes measurements, and adds shims in between the window’s rough opening and the jamb.

Next, the window’s measurements were re-checked to ensure proper placement of the shims and that the jamb had straightened.

Once this was confirmed, insulation was added between the rough opening and the jamb and the wall cladding was put back around the window:

For more extreme cases where time has had time to intensify uneven measurement and installation, the window may need to be removed so the rough opening can be adjusted or recut.

You'll want to consult with experts if you're unsure about the condition of your windows or if you are considering replacement windows. Brennan Enterprises offers 40 years of window replacement expertise. Contact us today at 817-860-9767 for a consultation to discuss your options for better-performing windows.

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