Why Does My Shingle Roof Feel Spongy When I Walk on It? [FAQ]

Does your shingle roof feel bouncy or spongy when you walk on it?

There are a variety of issues that can cause this problem. But we’ll look at the 3 most common. And for each one we’ll show you:

  • How to tell if that’s the problem you have
  • How to fix it

Let’s get started…

Old, inadequately supported roof

Many Phoenix-area homes have inadequate roof decking and/or rafter support by today’s standards. Old building codes allowed for thinner plywood (or OSB) decking and wider spaces between rafters.

And this construction often resulted in bouncy and spongy shingle roofs, like in this video.

Anatomy of a Shingle Roof
The anatomy of a shingle roof. Plywood decking sits on top of your rafters. The underlayment and shingles are attached to the decking. From our article, Anatomy of a Pitched Roof.

This is likely your problem if: Your whole roof, or large sections of your roof, are bouncy and your home was built prior to the 1990s.

How to fix it: Unfortunately, the only way to fix this problem is to tear off the entire roof and replace it with thicker decking. You may even need to add additional support between rafters.

Since this is such a big job, it’s usually best done when you’re replacing your shingle roof.

Related: How to Tell if Your Shingle Roof Needs to Be Replaced

Moisture/water leaks

Another reason for a bouncy roof is a little more serious: water damage. If your shingles and underlayment leak, water can get onto the plywood decking and rot it out.

This is likely your problem if: The bounciness is limited to one or a few areas of the roof.

Look in your attic for signs of moisture. Look at the underside of your roof decking, is it dark or discolored? Look at your insulation, is there any sign of mold or mildew?

Signs of Water Damage
Moldy insulation and other signs of moisture. Image source: Argus Roofing

How to fix it: You need to do 2 things here:

  • Replace the rotted/water damaged decking and wood
  • Fix the source of the water infiltration. In most situations, this is a leak somewhere above the water damaged decking.

Related: “My Roof is Leaking! What Should I Do? Who Should I Call?”

Inadequate attic ventilation

Inadequate attic ventilation can also cause your shingle roof to feel spongy or bouncy. Without good attic ventilation your roof gets extremely hot. And that extreme heat can damage both your shingles and the wood decking below them and causing your roof to feel soft when walking on it.

How attic ventilation keeps your roof cool and healthy. Image source: Red River Roofing

This is likely your problem if: You don’t have vents at both the top and bottom of your roof. Read more in our article, What’s the Best Way to Ventilate an Attic in Arizona?

How to fix it: You’ll need a licensed roofer to install the proper ventilation for your attic. You may also need to replace any damaged shingles and decking.

Need help with your bouncy/spongy roof?

If you live in the Phoenix or Tucson areas, contact Lyons Roofing. We’ve been providing Arizona homeowners with top-notch roofing service since 1993.