Roof sagging is a structural warning sign that needs attention as soon as you notice it. Any visible dip, curve, or low spot means part of the roof system is no longer supporting the weight the way it should.
Below, we clarify what normal looks like, when sagging becomes a problem, and how we approach the repairs that restore strength to the roof.
What Causes Roof Sagging?
Roof sagging usually happens for two reasons: weak sheathing or water damage. Both can cause the roof to lose shape over time.
Weak Roof Sheathing
The sheathing is the flat surface that supports your shingles. When the wood used is too thin, like 7/16-inch OSB, it can bend between rafters as years pass. We prefer using thicker 5/8-inch boards. They are stronger and last longer.
If your roof deck bends or dips, it often means the thin sheathing is giving way. This can spread and cause more dips, especially under conditions like snow or heavy rain.
Rotted or Wet Sheathing
Moisture is another big reason for roof sagging. If water leaks under shingles, it can soak the wood. Once the wood starts to rot, it weakens fast. You might notice soft spots or wavy areas. That means the decking under your shingles needs repair.
Pro Tip: Get your roof checked every year. Early signs of rot can be fixed before they lead to full sagging.
What Roof Sagging is Acceptable?
A tiny curve that you can’t see from the ground might not be a big problem. But if you can see a dip or wave in your roof line, that’s not acceptable.
Visible roof sagging means your roof has lost its support. It can lead to loose shingles, leaks, or even a roof collapse in bad cases. The moment it’s visible, it needs to be repaired.
Key Takeaway: If you can see the roof sagging, it’s time to call a roofer. Waiting too long can cause more damage and higher repair costs.
How We Fix Roof Sagging
Our repair steps depend on what’s causing the sag. We always start with a full roof inspection to find the problem.
Step 1: Remove Shingles and Check Decking
We take off the shingles to look at the wood underneath. This helps us find soft or rotted spots that need to be replaced.
Step 2: Replace or Strengthen the Sheathing
If we find rot, we replace those boards. If the whole roof was built with thin sheathing, we may install stronger 1/2-inch or 5/8-inch boards on top before adding new shingles.
Step 3: Check the Rafters or Trusses
In rare cases, the sagging can reach the rafters. We can reinforce them with new boards, known as “sistering,” to restore strength. Full replacement is only needed if the damage is deep.
Need expert help with roof sagging? Contact Precision Roofing for a free inspection. We’ll find the weak spots and help you fix your roof safely.
Will Insurance Cover Roof Sagging?
In most cases, roof sagging isn’t covered by home insurance. It’s only covered if caused by a storm or tree damage.
If the sagging comes from thin wood or old age, insurance won’t help. It’s seen as part of normal wear and tear. You’ll need to cover that repair yourself. Upgrading your sheathing is a good long-term fix that adds value and strength to your home.
When to Call a Roofing Expert
Don’t wait if you see your roof dipping. The problem only gets worse with time. Call a roofing expert if:
- You notice uneven lines or dips in your roof
- Shingles look raised or loose
- You see leaks or damp spots in the attic
We’ll inspect your roof, find the cause, and give you a clear repair plan.
In Summary
Roof sagging happens when the sheathing is too thin or has rotted from moisture. Once it’s visible, it’s not safe to ignore. The fix may include replacing or strengthening the decking.
Contact Precision Roofing today for a free inspection. We’ll check your roof, explain what’s wrong, and make sure your home stays safe and dry.
