A crack needs context: location, movement, water entry, and the surrounding masonry. Widening cracks, leaning, or loose masonry call for keeping clear and prompt professional evaluation.
Updated September 10, 2026
Your home in San Jose.
About 59% of occupied homes in San Jose heat primarily with utility gas. Many chimneys in San Jose therefore vent a gas furnace, boiler, or water heater rather than a wood fire, and those flues still need inspection for liner condition, moisture, and blockage. About 0.1% of occupied homes in San Jose use wood as their primary heating fuel. Most fireplaces in San Jose see occasional use, and even occasional use calls for an inspection before the heating season. The nearest NOAA climate normals station (San Jose, about 6 miles from the San Jose city center) averages 2,257 heating degree days per year. That is a moderate heating season, but moisture still reaches masonry year-round, so note when water appears and have the source investigated before choosing a surface treatment.
What you can observe safely
- Photograph visible cracks safely from ground level.
- Keep any earlier photos for comparison.
What to avoid
- Do not climb onto the roof or enter the chimney.
- Do not alter gas components, venting, or safety controls.
- Do not use a test fire to diagnose the problem.
Possible causes to assess
- Masonry or mortar deterioration
- Movement requiring assessment
- Water-related damage
A symptom cannot establish the cause remotely. An assessment of the complete system helps determine the appropriate repair.
Chimney repair in San JoseA few common questions
Can this be diagnosed from a photo?
A photo can document a symptom and help prepare a visit. It cannot confirm concealed conditions or establish that a chimney or fuel-burning appliance is safe.