What Are the Causes of Wavy Exterior Shingles & Walls?


Wavy exterior walls and shingle roofs may be caused by a number of culprits. Faulty framing or a weak plywood base is usually the cause, but improper nailing can lead to the same problem. Paying attention to these underlying problems can save you time and money down the road. Identifying and fixing the problems can prevent water infiltration at wavy spots.

Warped Wood

  • Many times when a wall or roof is framed, the framing members are warped and twisted. This causes roof framing to bow up or down, and it causes wall framing to bow in or out. Once siding or decking is installed over these framing members, then wavy roofing or siding results.

Misaligned Framing

  • When carpenters construct wall and roof framing, sometimes they fail to pull reference strings across the framing to check for misalignment. Therefore, when decking or siding is attached to misaligned framing, a wavy appearance is easily noticeable.

Weakened Structural Support

  • Weakened structural support is another major cause of wavy siding (walls) and roofing. When the framing members rot or the subdecking beneath the siding or roofing rots and bows, then the exterior materials such as siding and roofing shingles follow the natural path of the damaged materials beneath. Although it is difficult to determine whether or not that is the cause, removing some of the siding or roofing in order to determine the culprit may be necessary.

Defects in Materials

  • Defective siding and roofing also causes the appearance of a wavy application. Sometimes siding that is made for real wood products twists and bows after exposure to rain and sun. Metal and vinyl siding are also subject to expansion and contraction when weather is cold or hot. This movement can cause nails to work loose or even damage siding so that it appears wavy.

Improper Installation

  • Siding must be installed correctly in order to prevent its failure in the future. Usually, manufacturers recommend nailing siding every 12 to 16 inches to prevent bowing of the product. Manufacturers also recommend nailing roofing shingles every 12 inches to prevent the material from working loose. It is important to follow manufacturers' installation instructions when installing siding or shingles. Because not all materials are installed exactly the same way, reading instructions before installation can prevent improper installation and wavy aftereffects.

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  • "Black & Decker Complete Guide to Roofing Siding & Trim: Updated;" Chris Marshall; 2008
  • "Working Alone;" John Carroll; 2003
  • Photo Credit siding image by Psycience from Fotolia.com
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