What Causes a Sagging Roof?

A sagging roof is certainly an eyesore. Roofing lines are designed to be straight, not curved or drooping.

More important than your roof’s appearance, however, is its structural integrity. Sagging, especially when extreme, can be a warning sign that your roof may be headed for a collapse.


Taking care of your roof can help it remain sound for decades. But even if you’re diligent about maintenance and repair, any roof has the potential to droop. Understanding why can help you prevent a costly problem.

Water Damage Can Result in a Sagging Roof

All roofs are designed for optimal drainage. In Utah, proper drainage is even more important. Rain and melting snow flow toward the gutter system, which directs water away from the foundation.

When the gutter system is ineffective or flawed, or when damaged shingles impede the water flow, moisture can infiltrate the underlying wood deck and support structure, causing them to deteriorate. Poor ventilation can make the problem worse, because without proper air circulation, the water will sit and eventually permeate the surface.

Shingles and flashing offer some protection against water damage, but roofing isn’t impenetrable. If water sits for too long, especially if this occurs repeatedly, a sagging roof can be the unfortunate result.

A Sagging Roof Can Result from Too Much Weight

Structural problems can also cause your roof to droop. The roof is designed to handle a specific maximum weight load. Too much weight can create sagging.

Undersized rafters, inadequate internal bracing and other construction or design issues sometimes fail to provide adequate support. Snow and ice loads can also cause weight issues for northern Utah homes. Prolonged stress may result in sagging.

Removing snow and ice loads is risky, however. It may help prevent roof collapse, but without proper safety measures, the removal process could damage the shingles or tiles. Safety — both yours and your roof’s — is the primary reason that we recommend consulting with a professional roofing contractor for snow and ice removal.

Excess weight can also occur from too many layers of shingles. Utah building codes allow a maximum of two layers of roofing. If this is causing your roof to sag, licensed contractors will encourage you to do a full tear-off and replacement.

Other Causes of a Sagging Roof

A damaged or sinking foundation can also result in a sagging roof, as proper support is necessary for maintaining structural integrity. In northern Utah, settlement is a common cause of roofing problems, thanks to our unstable soil.

Finally, some roofing materials and installation methods can lead to sagging. Less expensive or lower-quality materials age faster, and as a result, may sag sooner. When you trust a reputable, licensed roofing contractor for your project, you can rest assured that the materials and workmanship are in accordance with today’s building code and safety standards.

A reputable contractor will also provide a warranty for their work.

Knockout Roofing, serving the greater Salt Lake City area, offers complimentary rooftop integrity consultations to homeowners throughout northern Utah. Contact us today to learn the best ways to avoid or repair a sagging roof.