Do Patio Doors Expand in Heat? (And What Action To Take)

I shut one side of the double doors to my garden office one particularly hot summer, and it just bounced back at me. It had become warped in the sun and wouldn’t close.

Depending on the materials they’re made of, patio doors can expand in the heat. Vinyl, fiberglass and wood patio doors can warp quite extensively in the sun, whilst aluminium and steel doors will experience little or no expansion when exposed to high temperatures for long periods of time.

Let’s consider the effect of heat on these materials in more detail, and establish how we can stop our patio doors from expanding in the sun in the first place.

Do Patio Doors Swell in Heat?

Do Vinyl Patio Doors Swell in The Heat?

Yes, vinyl expands in the heat – and shrinks in the cold. Most experts say that the expansion and contraction amount is about 1/16 inch. Surprising fact – that 1/16-inch heating or cooling gap around your vinyl doors and windows is equal to a brick missing from a wall!

Not only does the vinyl’s reaction to temperature result in thermal loss, but the expansion in summer can make the doors hard to open. The expansion can create gaps in the glass seal – allowing air in and fogging the glass in the patio door. When the vinyl door expands, it puts pressure on the track, the little slider wheels and even the locking mechanism.

The reality is that temperature will cause expansion and contraction of most materials. Vinyl begins softening at 165 degrees Fahrenheit. If that sounds like an incredibly high temperature, check it out with your infrared BBQ temperature gun. 

Vinyl, though, expands more than wood – by double the amount. Vinyl expands more than seven times more than the patio door glass it holds, creating those air leaks that lead to fogging. The bigger the glass and seal area, the more likely fogging will occur – a big problem with patio doors. To make matters worse, fogging is difficult to repair. For fogged patio doors, you must replace the door. Replacing vinyl windows and doors is a big business.

If you already have a vinyl patio door, here are some tips that may help.

How To Avoid Vinyl Doors Expanding

For vinyl patio doors, temperature is key. All vinyl windows expand and contract with temperature, but patio doors are especially affected because there is so much area. 

If your vinyl patio door is showing danger signs – sticking in the heat of the day, a little fogging – consider ways to decrease its temperature. If you live in a sunny, warm climate, where the full sun strikes the door – can you shade it?

Patio umbrellas can be placed to shade the door during the noonday sun. How about planting a tree or moving a potted one? Consider a bright, beautiful awning over your patio door. Any kind of shade will help a vinyl door. Some experts suggest cooling down your door with a hose or sponges. 

In the winter, in cold climates, consider ways to keep the door warm. After caulking around the door, remove or open the curtains. An awning or overhang outside over the door will keep snow from piling up against the glass. In the winter, sunshine against your patio door is a good thing.

A window expert can recommend other ways to avoid vinyl expansion and contraction: welding corners, embedding steel or aluminum bars inside the frame, changing the color of the frame, or installing shims or screws.

Do Aluminum Patio Doors Expand in The Sun?

Most experts agree that if aluminum patio doors expand at all – the expansion is minimal. But aluminum frames may bow and twist – temporarily. Thermal bow may make your aluminum doors hard to open or latch. Aluminum doors bow out when the summer sun is hitting the frame. They bow in when the air outside is freezing but the inside is toasty.

Aluminum is a strong metal, so frames can be slimmer – and the glass larger. Glass can be surprisingly energy efficient. Aluminum patio doors are more lightweight. They don’t rot, peel or flake. Aluminum, though, is a conductive metal. It transfers cold or heat with ease.

Consider an aluminum patio door with noonday sun on the outside and air conditioning on the inside. With rapid changes and extreme temperatures on either side, aluminum frames tended to bow or twist temporarily. Thermal bowing is a natural reaction to the temperature difference and goes away when the temperatures equalized.

On freezing cold days, older aluminum doors transfer the cold to the inside door frame. Same with blazing heat. Today, aluminum patio doors don’t transfer the heat from the outside to the inside because of – thermal breaks.

To decrease the negative effects of aluminum’s natural conductivity, doors today can be purchased with “thermal breaks”. Thermal breaks cut the heat or cold transfer from the outside patio door frame to the inside one.

To do this, a non-conducting (insulating) material – plastic – is used to join the outside frame with the inside one. Thermal breaks stop thermal transfer. Thermal breaks stop the bowing or twisting that can occur temporarily when the outer frame is blazing hot and the inner frame is cold.

Thermally broken aluminum patio doors are widely available and are a good choice for a wide range of climates.

How To Stop Aluminum Doors Swelling

For aluminum patio doors in hot, sunny climates, try shading them. Like vinyl doors, aluminum doors will last longer with fewer problems with as little direct, summer sun as possible. Arrange your patio umbrella to shade it during the heat of the day. Consider an awning or overhang – even small ones will help when the summer sun is overhead.

Plant trees or move patio umbrellas to spots that give some shade. Consider painting the door a light, reflective color.

When purchasing a new aluminum patio door, be sure it’s thermally broken.

Do patio doors warp in the sun?

Do Wooden Patio Doors Swell Up When Hot?

Yes. Wood is naturally porous. Swelling in wooden doors is caused by moisture – humidity. In the heat of the summer, humidity in lots of climates rises and wooden doors start sticking. In the summer, wooden doors in the full sun are prone to swelling. 

In many places, outside humidity in the summer can reach over 90 percent. Research shows that areas with humidity over 70 percent can cause property damage. Inside, health experts say that an ideal humidity range is between 30 and 50 percent.

Tips For Stopping Wooden Doors From Swelling

The best way to stop wooden doors from swelling is maintenance. New wooden doors are waterproofed with sealants or paint. But in the direct sun, wood sealants crack, peel and blister. Often, replacing the sealant or giving your door a fresh coat of top-quality paint will help door swelling. Sand or strip off the old sealant before resealing. Make sure that the door is good and dry before applying sealant or paint.

Find ways to reduce the humidity at the door. Open your windows – unless there’s more humidity outside! Try a dehumidifier if your house is over 50 percent humidity.

As always, the full strength of the sun in the summer damages doors. Try to find some shade for your door. A beautiful awning. An overhang. A tree. Paint your wooden frame with a light, reflective color.

Do Steel Patio Doors Warp in The Heat?

They can. Warping is a distortion of the shape. Steel doesn’t conduct heat or cold as well as aluminum does. But if one side of a door is hotter than the other side, warping or bowing can occur. As with aluminum doors, extreme temperature differences from the inside to the outside can bow, twist, or distort a steel frame.

If you are considering a new steel door, be sure to buy a thermally broken one.

How To Stop Steel Doors Warping

Steel patio doors are manufactured with the same thermal break feature as aluminum ones. Thermal breaks allow the inside frame to have a different temperature from the outside frame. A thermally broken frame will prevent any bowing, twisting or distortion.

Consider shielding the exterior side of the patio door with an awning or a cover. Give shade with a tree or an umbrella. Install an overhang.

Paint your steel door a light color to reflect bright sunshine.

Do Fiberglass Patio Doors Swell in The Sun?

Mother Nature is harsh. Direct summer sun is harsh. Although a low-maintenance choice, fiberglass can swell, warp and crack

When buying a fiberglass patio door, make sure the fiberglass is high quality. Low quality fiberglass will crack in the full sun and will need more maintenance over its lifespan. If the door doesn’t come presealed, apply an exterior-grade, high quality, UV-stabilized sealant.

Good quality fiberglass doors are durable and surprisingly strong. Fiberglass doesn’t rust, twist, bow or warp.

How To Stop Fiberglass Doors Swelling

As always, to avoid harsh, high temperatures of direct sun in summer – add shade. Awnings. Overhangs. Trees. Move your patio umbrella to give some shade.

Painting with lighter colors help preserve the fiberglass by minimizing the heat absorption. Some experts suggest painting with a high gloss finish will help deflect the sun’s rays. Gel stains that have UVL protection are good choices. 

To avoid fiberglass door swelling, make sure that the original installation is snug. Apply an exterior, high quality, UV protection yearly to fiberglass. Some experts suggest applying furniture polish, or spray-on marine wax.

Conclusion

Patio doors constructed of certain materials can indeed expand when exposed to heat for long periods.

That’s why it’s important to introduce umbrellas, awnings and strategic tree and shrub planting to protect your doors from extended exposure to hot sunlight.

While aluminum and steel patio doors won’t warp too much in the heat of a summer’s day, you’ll find vinyl, wood and fiberglass doors will – so it’s a good idea to treat them in the ways described or add some shade where possible.