Why does my UPVC door stick in the sun, and how can I fix it?

 UPVC doors, made of a heat-resistant plastic, still experience some expansion when exposed to sunlight or high temperatures. The absorption of heat from sunlight causes the molecules in the door to move more vigorously, increasing their kinetic energy. Consequently, the molecules push against each other, leading to slight expansion in the door's dimensions, such as length, width, or height.

In simpler terms, as the temperature rises, UPVC doors expand. 

In most cases, when you leave your UPVC door open during hot weather and attempt to close it later in the day, you may encounter resistance or difficulty closing it. This is because the door has expanded and may require a stronger push to shut. However, if the door is within its frame, the frame restricts the door's expansion, making it easier to open. The most significant expansion occurs when the door is not restricted by the frame. 

To estimate the thermal expansion of your UPVC door, you can use the following formula as a rough guide: Length of UPVC in mm X 0.00006 X Increase in Temperature = Amount of expansion in mm. 

For example, let's consider average 6ft (2mm) French doors with a temperature change from 12 degrees (night) to 32 degrees (day). Assuming the UPVC temperature is the same (it could be more or less due to direct sun), the calculation would be: 

1800mm x 0.00006 x 20 Degrees = 2.6mm Expansion 

Please note that this is only an approximate guide, as there can be variations based on different factors.

To cool down your UPVC door, you can try the following methods:

1. Provide shade: If possible, move the door to a shaded area where it is not directly exposed to sunlight. This will help reduce the temperature of the door and minimize thermal expansion. However, this may not be practical for most situations. 

2. Use cool water: Spraying cool water on the door's surface can help lower its temperature. As the water evaporates, it absorbs heat from the door, aiding in cooling. Be cautious not to use hot water, as it may cause further expansion. This method is particularly useful for outward opening doors, where you can simply use a hosepipe to cool them down for a few minutes. 

Remember, while these methods may provide temporary relief, UPVC doors are designed to withstand some expansion and should return to their original dimensions once the temperature decreases.

The key to all of this is patience if you have the time, you can  call a service engineer out and they will shut it but it could cause problems later on in the year.

So, make a brew, enjoy the sun & wait for a cloud to come along or for the temperature to drop.