# How much does it cost to repair a sagging roof?

*Published 2026-05-31T09:00:00-07:00 · Updated 2026-07-18T09:00:00-07:00 · Best Roofing Answers*

## Answer

Repairing a sagging roof typically costs $1,500–$7,000 for localized decking replacement, $3,000–$12,000 for rafter sistering or reinforcement, and $10,000–$25,000 or more when structural trusses have failed and engineering is required; costs vary by span, cause, and whether load-bearing members are compromised.

## Sag is a structural symptom

A visible sag between rafters or across a roof plane is a structural signal, not a cosmetic one. Per NRCA and IRC Chapter 8, common root causes are (1) rotted decking from a chronic leak, (2) under-sized rafters relative to snow or dead load, (3) failed truss webs or connectors, and (4) removed load-bearing walls below. Diagnosis dictates the fix.

Any roof with a truss-related sag should be evaluated by a licensed structural engineer before repair. Cosmetic patching over a structural sag is a code violation in most jurisdictions and typically voids homeowner's insurance if it later collapses.

## Also asked as

- sagging roof repair cost
- how much does it cost to fix a sagging roof
- cost to replace rotted roof decking
- sagging roof structural repair estimate

## Sources

- [International Residential Code (IRC), Chapter 9 — Roof Assemblies](https://codes.iccsafe.org/content/IRC2021P2/chapter-9-roof-assemblies) — Chapter 8 — roof/ceiling construction loads
- [NRCA (National Roofing Contractors Association)](https://www.nrca.net/)

## Related

- https://bestroofinganswers.com/decision/repair-vs-replace-roof
- https://bestroofinganswers.com/q/what-causes-a-sagging-roof
- https://bestroofinganswers.com/q/when-does-roof-decking-need-replacement

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Published: 2026-05-31T09:00:00-07:00
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