Siding
Melted Vinyl Siding: Grills, Window Glare, and Fixes
Vinyl siding melts or warps when something heats it past what it was made to handle. The two most common causes are a grill set too close to the wall and sunlight reflected off a nearby window, often an energy-efficient Low-E window. The fix has two parts: remove or block the heat source, then replace the damaged panels. If you skip the first part, the new panels will warp too.
July is peak grilling season, and the summer sun is at its strongest. This is when I hear the most about wavy, sagging siding. Here is how to figure out what caused yours and what to do about it.
What does melted vinyl siding look like?
Heat damage usually looks like one of these:
- Panels that sag, bulge, or ripple in one area
- A wavy streak or patch, often shaped like a stripe or an oval
- Panels that pulled away from the wall or out of their locks
- Gloss or color changes in a patch, sometimes with soot nearby
Not every wavy wall is heat damage. Vinyl that was nailed too tight also buckles. The Vinyl Siding Institute installation manual says tight nailing "will cause the vinyl siding to buckle with changes in temperature." Buckling from nailing usually runs along whole panels and shows up on many walls. Heat damage is usually one spot.
How can you tell what melted your siding?
| What you see | Likely cause | Clues |
|---|---|---|
| Sagging or melted patch at about grill height, maybe with soot | Grill, smoker, or fire pit | It lines up with where you cook |
| Wavy stripe or oval in an open area of wall | Sunlight reflected from a window | A window faces this wall, on your house or the next one |
| Damage near the ground | Burning leaves, mulch, or trash | Scorch marks or burned material nearby |
| Waves along full panels on several walls | Tight nailing, not heat | No heat source nearby |
To check for window reflection, stand at the damaged spot on a sunny afternoon and look for a window aimed at you. It may be your own window on another wing of the house, or your neighbor's.
Why can a window melt vinyl siding?
The Vinyl Siding Institute published a paper on the effect of concentrated sunlight on vinyl siding. Here is what it says:
- Low-E glass "reflects a greater percentage of incident sunlight than normal glass, especially in the infrared (heat) part of the spectrum."
- Ordinary sun plus a normal flat window does not usually get vinyl hot enough to distort.
- In most cases, the window glass has bent slightly inward. That happens when the air pressure between the two panes differs from the air outside. The curved glass works like a magnifying mirror and focuses a beam of sunlight onto the siding.
- Because the beam is so intense, "both light and dark colors can be affected."
Because the beam depends on the sun's angle, a window may only cause trouble at certain times of day or certain times of year.
How do you stop window reflection damage?
The Vinyl Siding Institute paper says anything that blocks the path of sunlight to the window, or between the window and the siding, will reduce or stop the problem. Its suggestions include:
- Window screens. A screen on the window can cut the reflected energy enough to stop the damage.
- Awnings or sunshades over the window.
- Trees, shrubs, or other landscaping placed to block the beam.
It also suggests contacting the window and siding makers about your situation.
If the window belongs to a neighbor, talk with them. Show them the damage and the timing. A screen on their window is often the simplest fix, and it is their call. Your homeowners policy may or may not cover the damage. Ask your agent.
How far should a grill be from vinyl siding?
Follow the clearances in your grill's manual. The NFPA grilling safety tip sheet says the grill "should be placed well away from the home, deck railings and out from under eaves and overhanging branches."
CertainTeed's vinyl siding warranty includes a fire safety note. It says vinyl "will melt or burn when exposed to a significant source of flame or heat." It tells owners to keep barbecues, dry leaves, mulch, and trash away from vinyl siding.
Fire pits, patio heaters, and smokers deserve the same caution. Heat rises, so soffits and siding above a grill take heat too.
Does the siding warranty cover melted siding?
Usually not. CertainTeed's warranty linked above excludes "distortion or melting" due to "external heat sources, including but not limited to, barbeque grills, fires or as a result of reflection from windows, doors or other objects." Other makers have similar terms. Homeowners insurance is a separate question that depends on your policy.
How are melted vinyl panels replaced?
The good news is that this is usually a small repair. Vinyl siding is built to come apart one panel at a time. The Vinyl Siding Institute manual describes the method:
- A zip tool unlocks the panel above the damaged one.
- The installer bends that panel out and pulls the nails from the damaged panel.
- A new panel locks into the course below and is nailed loosely, in the center of the slots.
- The zip tool locks the upper panel back over the new one.
Matching is the tricky part. Siding fades, and colors get discontinued. On older siding, we sometimes move a panel from a hidden wall to the damaged spot and put the new panel where it will not show.
Before we replace anything, we look at the sheathing and house wrap behind the damaged area. The Vinyl Siding Institute paper notes that reflected sunlight has damaged weather barriers too.
Can you heat warped vinyl and push it back flat?
I would not try. Once vinyl distorts, it does not go back to flat and straight. It also may have pulled loose from its locks. Replacing the panel is the reliable fix.
How Shamrock can help
We repair and replace vinyl siding across Northern Cincinnati. We will help you find the likely cause so the new panels do not warp again, and we will tell you if a match is hard to find. See our siding services or request a free estimate.
FAQ
Does dark vinyl siding melt more easily than light siding? Darker colors absorb more heat from direct sun. But for reflected sunlight, the Vinyl Siding Institute says the beam can be so intense that both light and dark colors are affected. Color is a secondary factor.
Is melted siding a fire hazard? Warping happens far below the temperature where vinyl catches fire. The Vinyl Siding Institute manual says PVC will not ignite from a flame until about 730°F. Still, if a grill melted your siding, the grill is too close. Move it.
Can I paint over a melted spot? Painting will not fix the shape, and it can affect your warranty. CertainTeed's warranty is void on siding painted over the original finish without its approval.
Would fiber cement siding solve the problem? It can be an option near a grill area or a problem window. Our guide to fiber cement vs vinyl siding compares the two.