Finding a "wave" in your home’s exterior is more than just an aesthetic issue; it is a signal that your home’s protective envelope has been compromised. In the Chicagoland area, our extreme temperature swings from -20°F winters to 95°F humid summers make siding particularly vulnerable to physical distortion.

If you’ve noticed buckling, bulging, or warping, here are the five most common culprits we see in Illinois homes in 2026.


1. Thermal Expansion & Improper Nailing

Vinyl siding is designed to "float" on your house. Because PVC expands and contracts significantly with the temperature, it cannot be nailed tight to the wall.

  • The Problem: If a contractor drives nails too deep (pinning the panel) or fails to center the nail in the slot, the siding has nowhere to go when it heats up.

  • The Result: The panel is forced to bow outward, creating a permanent "wave" or buckle.

2. Reflected Sunlight (The "Magnifying Glass" Effect)

With the rise of high-efficiency, Low-E (low emissivity) windows in neighboring homes, we are seeing a new phenomenon: siding literally melting.

  • The Problem: Highly reflective window coatings can act like a magnifying glass, focusing a concentrated beam of solar energy onto your siding.

  • The Result: Even premium vinyl siding can reach its "heat distortion point" (around 160°F–165°F), causing it to sag and warp in a very specific, localized pattern.

3. Moisture Trapped Behind the Panel

Warping isn't always about the siding material itself; sometimes it’s about what is underneath.

  • The Problem: If your house wrap is damaged or your waterproofing system is failing, moisture can get trapped between the siding and the wood sheathing.

  • The Result: As the wood absorbs moisture and swells, it pushes against the siding from the inside out, causing the panels to look buckled or uneven.

4. Poor Quality "Thin-Gauge" Materials

In a volatile climate like Illinois, material thickness matters.

  • The Problem: Economy-grade vinyl is often too thin to maintain its structural integrity over time.

  • The Solution: This is why we often recommend James Hardie fiber cement for homeowners looking for long-term stability. Because it is a masonry-based product, it does not expand or contract like plastic, meaning it will never warp or melt.

5. Settling and Structural Movement

Sometimes the siding is just the "messenger" for a deeper issue.

  • The Problem: If your home's foundation is shifting or your wall studs are twisting due to age, the siding will be forced out of alignment.

  • The Warning Sign: If you notice warping appearing suddenly after a season of heavy rain or drought, it may be time to check for foundation moisture problems .