Why Does My Roof Look Wavy?
A roof should appear relatively straight and uniform when viewed from the ground. It should not dip, ripple or look uneven. Minor waviness does not always indicate an urgent problem, but it should be inspected by a roofing professional.
The cause of a wavy roof isn't always obvious without a closer look. Several different factors can affect the appearance of your roof, ranging from aging materials to problems beneath the shingles themselves.
Uneven Roof Decking
Roof decking, also called roof sheathing, is the layer of plywood or oriented strand board (OSB) attached to the roof framing. Shingles and other roofing materials are installed on top of this surface.
If sections of the decking become uneven, the roofing materials installed above them will follow those contours. This can create visible dips or raised areas across the roof.
Uneven decking may occur because of:
- Natural settling of the home's structure
- Improper installation during construction
- Water damage that weakens portions of the decking
- Previous repairs that weren't properly leveled
While slight irregularities may not immediately affect performance, larger variations should be evaluated to determine whether repairs are needed.
Warped or Damaged Decking
Small roof leaks, poor attic ventilation or long-term humidity issues may allow wood panels to absorb moisture and gradually change shape. As the decking expands, contracts or weakens, the roof surface above it may begin to appear uneven.
Signs that warped decking may be contributing to a wavy roof include:
- Noticeable sagging between roof framing members
- Soft spots when walking on the roof (only a professional should inspect this)
- Water stains in the attic
- Areas where the roof seems to dip more noticeably after heavy rain
Because damaged sheathing affects the structural support beneath the roofing material, these situations should be inspected promptly.
Multiple Layers of Old Roofing
In some cases, a roof looks wavy because a new layer of shingles was installed over an existing roof instead of removing the old roofing first. Reputable roofers generally discourage this type of reroofing because it can conceal damage to the roof deck and cause the new shingles to follow imperfections in the layer beneath them.
Additionally, multiple roofing layers add extra weight to the structure and can make future inspections and repairs more difficult.
When it's time for a roof replacement, a complete tear-off of the old materials allows the decking to be inspected so any hidden problems with the decking can be corrected before the new roofing is installed.
Installation Issues
Not every wavy roof is caused by aging or structural problems. Sometimes the appearance results from installation errors. Examples include:
- Roofing materials installed over an uneven surface
- Shingles that were not properly aligned
- Improper fastening techniques
- Inadequate spacing between roof decking panels
- Flashing or underlayment installed incorrectly
Experienced roofing contractors take care to ensure the roof deck is flat and stable before installing new roofing materials. Skipping this preparation can leave homeowners with a roof that looks uneven from the very beginning.
If a roof develops waviness shortly after installation, it's worth having the work inspected to determine whether installation quality played a role.
Cosmetic vs. Structural Problems
Cosmetic waviness may include:
- Minor ripples that have existed for years without changing
- Slight variations caused by natural wood framing
- Small imperfections that don't affect drainage or roof performance
Structural concerns may include:
- Large or growing dips in the roofline
- Sagging ridges
- Areas that collect standing water
- Signs of water intrusion inside the home
- Soft or deteriorated roof decking
Don't Ignore Changes in Your Roof's Appearance
A roof rarely changes appearance without a reason. Even if a wavy roof isn't currently leaking, visible changes can sometimes indicate developing problems beneath the surface.
The experienced team at Chet's Roofing & Construction can perform a thorough inspection to determine whether uneven decking, warped sheathing, old roofing layers or installation issues are affecting your roof in Seattle. We'll explain what we're seeing, recommend the appropriate solution and help you protect your home with honest, professional service.
Contact us at (877) 611-1514 to schedule your roof inspection.
