Is It Important For Vinyl Windows To Be Level?

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Mar 11, 2015

Feb 28, 2024

3 min read


“What a stupid question. Of course, it is.” you’re probably saying. And technically you’re not wrong. It is a MUST for any window installer to bring a leveler to any installation. But while your vinyl windows and doors should be installed square and level, the end result may not always be aesthetically pleasing in your home. We’ll explain why.

While it’s important for your vinyl windows to be installed level, the walls in your home may not always be perfectly straight. This may result in new windows looking uneven in the wall.

Canadian Window Installation Standards

The Canadian Standards Association even has very specific guidelines as to the allowable offset when it comes to window replacement.

As per CSA window installation guidelines, a frame is level when the sill is horizontal and the vertical difference of one side compared to the other is 2 mm (1/16 in) or less.

A frame is square when the height and width of the frame measured in the middle is the same as the average height or width ±1 mm (1/32 in) and when
(i) the difference between the two diagonals is less than or equal to 2 mm (1/16 in) for a frame with exterior perimeter less than or equal to 4 m (13 ft); or
(ii) the difference between the two diagonals is less than or equal to 3 mm (1/8 in) for a frame with an exterior perimeter greater than or equal to 4 m (13 ft)

Another important thing to consider is the plumbness of your custom windows. This refers to how parallel the window is to the wall it is installed in. In this case, you want the top of the frame to be leaned out just slightly. This offset usually shouldn’t be visible to the human eye. If vinyl windows are installed straight, rain water will simply gather on the sill and not drain away from the home. In operable windows, water would simply sit in the drainage channels, and not drain out.

But believe it or not, what is technically and structurally right for your house, may not always be what looks the best. It is difficult (or heartwarming depending on your personality type) to think of your house as a living thing, but in some ways that’s exactly what it is. Even years after it has been built your house may continue to settle. Over time, weather elements can warp and change the shape of materials in your home. This is especially true for really old homes. Actually, getting new windows is a good way to minimize that, but that’s a story for another blog. Bottom line is, once installed correctly, the lines on your windows may not match up to the lines of your counter tops or floors, making it seem like the window is off-level. Unfortunately, there is no solution to make the lines seem square.

Installing windows to match the slant in the walls of your home will ultimately create more problems down the road as they will trap water rather than push it away from your home.

Check out these window replacement articles:
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Get answers to most frequently asked questions
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