3:12Decision guide
Repair or Replace Your Roof?
Replace when the roof is near the end of its rated life and the problems are spread across it: granule loss everywhere, several leaks, tired underlayment under tile, or a soft deck. Repair when the damage is local and the rest of the roof has years left.
Active leak? Call (925) 281-5910
4:12Checklist
Signs that point to replacement
Age
Architectural shingles past about 20–30 years, 3-tab past 15–20 (HomeGuide). Tile itself lasts far longer; its underlayment does not.
Granule loss
Bare, shiny patches on shingles and granules in the gutters mean the asphalt is exposed to sun.
Curling and cracking
Cupped, clawed or cracked tabs across several slopes, not just one corner.
More than one leak
Separate leaks in different areas suggest the underlayment is done, not one bad flashing.
Cracked or slipped tiles
A few cracked tiles can be swapped; many slipped tiles and stains below usually mean failed underlayment.
Sagging or soft deck
A dip between rafters or a spongy feel underfoot means rotted sheathing. Get it inspected soon.
Previous patches
Mismatched patches across the roof often mean you are paying for a new roof in installments.
The informal 25% rule next to the two 50% thresholds that appear in California rules.
3:12The 25% rule
What the "25% rule" really is
Search for repair vs. replace and you'll meet the "25% rule": if more than a quarter of a roof needs work, replace all of it. It is a rule of thumb usually traced to building codes outside California. It does not appear in the California state rules we cite.
The thresholds that do appear are both 50%:
- Class A in very high fire zones. HSC §13132.7(d) requires at least a Class A covering on an existing structure "where more than 50 percent of the total roof area is replaced within any one-year period" (statute). Fire-zone details.
- Cool roofs. "Cool roofing requirements are triggered when 50% or more of the roof is being replaced" (BayREN).
Local codes can add more, so the building department's answer for your address is the one that counts. See the permit and rules table.
5:12Partial re-roofs
Replacing part of a roof
Replacing one slope or one section can make sense when it is a separate plane, a low-slope porch, or a newer addition. Expect three problems:
- Matching. Shingle colors change between production runs and old shingles have weathered; the new section will look different.
- The tie-in. The seam between old and new is a classic leak point and has to be flashed carefully.
- The thresholds. Replace half or more and the cool-roof rule applies; replace more than half in a very high fire zone and the Class A rule does too.
4:12When repair wins
When a repair makes sense
- The roof is in the first half of its expected life.
- The leak traces to one spot: a pipe boot, a chimney or skylight flashing, a valley, wind-lifted shingles.
- On tile: a handful of cracked tiles over sound underlayment.
- You plan a full replacement soon and need to stay dry until then.
Next: what a replacement costs · tile roofs · flat roofs
Leak, or just wondering?
A roofer can tell you whether a repair buys real time or just delays the inevitable.
3:12FAQ
Questions homeowners ask
What is the 25% rule in roofing?
An informal rule of thumb: if more than about a quarter of the roof needs repair, replace the whole roof. It is usually traced to building codes outside California, not to the California state rules cited on this site. In California, the citable re-roof thresholds are 50%: the Class A requirement in very high fire hazard zones (HSC §13132.7) and the cool-roof requirement (Title 24, per BayREN). Your building department has the final word.
How long does a roof last?
HomeGuide lists 3-tab asphalt at 15–20 years, architectural shingles at 20–30, wood shakes at 25–30, metal at 30–80+ and tile at 30–100+. On tile roofs, the underlayment under the tile wears out long before the tile does.
Can I replace just half my roof?
Sometimes. A separate roof plane, a flat section or an addition can be replaced alone. The catches: new shingles rarely match weathered ones, the seam between old and new is a common leak point, and replacing 50% or more can bring the whole roof under cool-roof or Class A rules.
Will insurance pay for a new roof?
Policies generally cover sudden damage, such as a tree limb or wind, not wear and age. Ask your insurer before work starts, and be wary of anyone who promises the claim outcome.
12:12Quote
Get a roofer's opinion on repair vs. replace
Have a leak right now? Calling is fastest. Otherwise, send the details and a local roofer can inspect and tell you which way the numbers point.
- Composition, tile, flat and metal roofs
- Walnut Creek, Lafayette, Orinda, Danville and nearby
- Prefer to talk? (925) 281-5910