Repair or Replace? How a St. Louis Roofing Contractor Decides

Five questions a roofer asks before recommending repair vs. replacement, and the math on what each actually costs over the next decade.

Every roofing contractor in St. Louis hears the same question: 'Do I need a new roof, or can I just repair this?' The honest answer is — it depends, and the contractor who reflexively says 'replace' on every visit is probably not the one to hire.

Here are the five questions we walk through with every customer before making the call.

1. How old is the existing roof?

Architectural asphalt shingles in the Midwest typically last 18–25 years. If your roof is under 12 years old, repair is almost always the right answer — even for serious damage. The remaining shingles have years of usable life left, and a repair preserves that investment.

Between 12 and 18 years, it's a judgment call. We weigh the size of the damage area against the cost of repair vs. the proximity to the natural end of the roof's life.

Over 18 years on architectural shingles? Repair is almost always throwing good money after bad. The rest of the roof will need replacement within a few years, and repair work doesn't extend the overall lifespan.

2. What's the damage scope?

A few damaged shingles in one area — repair. Damage spread across multiple slopes — usually replacement. The threshold most contractors use is the 30% rule: if more than 30% of the roof shows damage, replacement is more cost-effective per remaining year of service.

This is also where storm damage matters. A roof with damage from a single recent storm event can often be repaired (or insurance-funded for full replacement). A roof with cumulative damage from multiple storms over multiple years is usually past repair.

3. Is the deck still sound?

This is the question most ground-level inspections miss. If we open up a roof and find soft, water-damaged, or rotted decking, repair is no longer an option — the structural substrate is compromised.

Signs your deck may be soft from inside the attic: dark staining around any roof penetration, soft spots when you press on the underside of the deck, daylight visible through the deck boards. Any of these on inspection day means we're talking replacement, not patch.

4. What's the energy and code situation?

Code has changed significantly since most St. Louis homes were last re-roofed. Current Missouri code requires synthetic underlayment, ice-and-water shield at eaves and valleys, and proper ventilation. If your existing roof predates these requirements and is approaching end of life, a replacement brings the whole assembly up to current code and locks in 25 more years.

A repair on an older roof can't address ventilation or underlayment — you'd be sealing those problems back inside the existing system.

5. What's the 10-year math?

This is the question that decides most close calls. We project two scenarios:

Scenario A — Repair now. Cost of repair plus the eventual full replacement when the roof fails in 3–5 years.

Scenario B — Replace now. Single cost, 25-year warranty, no further work needed.

If Scenario A's total cost is within 30% of Scenario B's, replacing now wins. You stop paying for a roof that's already failing and you reset the clock on warranty coverage. If Scenario A's total cost is meaningfully lower, repair is the right call.

Where we land most often

Across the St. Louis market we see roughly: 50% of inspection calls end up as repair-only (and we tell the homeowner that, even when they came in expecting a replacement quote), 30% end up as recommended-replacement with no urgency, and 20% are urgent-replacement situations driven by leak severity, deck rot, or storm damage.

If you've got a contractor pushing replacement on a 10-year-old roof with isolated damage — get a second opinion. We do free inspections, we tell you exactly what we'd do if it were our own house, and we document everything so any next contractor can verify.