Case Study: Olympia Leak Repair — Sheathing Replacement, Flashing Fixes, and Final Costs

This case study documents a roof leak repair on a 1985 ranch-style home in Olympia's Westside neighborhood. What started as a small ceiling stain revealed years of hidden water damage that required significant repair work.

The Discovery

The homeowner noticed a small brown stain on their master bedroom ceiling after a heavy December rainstorm. The stain was about 6 inches across and appeared to be growing slowly. By the time they called for an inspection in early January, the stain had expanded to nearly 2 feet.

Professional Inspection Findings

A licensed Thurston County roofing contractor conducted a comprehensive inspection:

Exterior Findings:

• Chimney flashing had separated from the masonry on the south side
• Step flashing at the chimney-to-roof transition was corroded and improperly overlapped
• A 4x6-foot section of shingles near the chimney showed advanced granule loss
• Moss growth covering approximately 20% of the north-facing slope

Interior/Attic Findings:

• Water trail visible on rafters leading from the chimney penetration
• Sheathing rot in a 3x4-foot section around the chimney
• Wet insulation in a 6-foot radius
• Early mold growth on the affected sheathing (caught before it spread to framing)

Scope of Repair

The repair scope was more extensive than a simple shingle patch:

1. Remove shingles and underlayment in the chimney area (approximately 100 sq ft)
2. Remove and replace rotted OSB sheathing (3x4-foot section)
3. Treat exposed framing with mold-inhibiting solution
4. Install new ice and water shield around chimney
5. Install new step flashing and counter flashing at chimney
6. Reinstall underlayment and shingles to match existing roof
7. Remove and replace wet insulation
8. Moss treatment on north-facing slope
9. Seal and prime ceiling stain (drywall repair by separate contractor)

Timeline

Day 1 (4 hours): Removed shingles and underlayment around chimney. Exposed and documented sheathing damage. Cut out rotted sheathing section.

Day 2 (6 hours): Installed new OSB sheathing. Applied mold treatment to exposed framing. Installed ice and water shield. Fabricated and installed new step and counter flashing.

Day 3 (4 hours): Installed underlayment, matched shingles, and completed the roof surface. Applied moss treatment to north slope. Final cleanup and walkthrough.

Total active work time: 14 hours over 3 days

Cost Breakdown

Additional costs (separate contractors):

• Drywall repair and paint: $450
• Grand Total: $3,975

What Could Have Prevented This

1. Annual chimney flashing inspection — the flashing separation likely began 2–3 years before the leak appeared
2. Moss treatment — the moss on the north slope was contributing to moisture retention near the chimney area
3. Proactive flashing replacement — reflashing a chimney costs $600–$900 as a preventive measure vs. $3,525 as a reactive repair
4. Gutter maintenance — overflowing gutters had contributed to water running behind the flashing

Homeowner Takeaways

• Don't ignore ceiling stains — a 6-inch stain became a $4,000 repair in just one month
• Chimney flashing is the #1 leak source in Western Washington homes over 15 years old
• Annual inspections catch problems at $200–$400, not $4,000
• Moss contributes to leaks even when it's not on the exact failure point — moisture retention on one section affects adjacent areas
• Get repair estimates quickly — water damage grows exponentially in Olympia's persistent rain

This Olympia repair demonstrates why preventive maintenance is the most cost-effective roofing strategy in Western Washington. The homeowner now schedules annual inspections and moss treatments — an investment of about $600/year that prevents thousands in reactive repairs.