Question? Just ask us!
Free Encyclopedia of Building & Environmental Inspection, Testing, Diagnosis, Repair
InspectAPedia ® Home
CHIMNEY INSPECTION DIAGNOSIS REPAIR
BACKDRAFTING HEATING EQUIPMENT
CARBON MONOXIDE - CO
CHIMNEY COMPONENT DEFINITIONS
CHIMNEY FIRE ACTION / PREVENTION
COMBUSTION GASES & PARTICLE HAZARDS
COMBUSTION PRODUCTS & IAQ
FLAME COLOR, BLUE vs YELLOW COMBUSTION
HEATING SYSTEM INSPECTION
HOME HEATING SAFETY
ODORS & SMELLS DIAGNOSIS & CURE
SAFETY RECALLS CHIMNEYS VENTS HEATERS
STAIN DIAGNOSIS on BUILDING EXTERIORS
WOOD, COAL STOVES & FIREPLACES
WOOD STOVE SAFETY
How to diagnose indoor stains at chimneys or caused by chimney problems. This article describes procedures for inspecting and repairing chimney flues - focused on stains that appear on the exterior surfaces or visible surfaces of chimney walls inside buildings.
© Copyright 2012 InspectAPedia.com, All Rights Reserved. Use page top links to major topics or use links at the left of each page to navigate within topics and documents at this website. Green links show where you are in a document series or at this website.
The pair of photos above teach several important chimney inspection lessons:
These articles on chimneys and chimney safety provide detailed suggestions describing how to perform a thorough visual inspection of chimneys for safety and other defects. Chimney inspection methods and chimney repair methods are also discussed.
Leaks originating at a chimney top, sides, even at ground level as well as chimney interior moisture sources (condensation) can all show up as stains on building interior walls at or near surfaces where the chimney passes through the building.
Indoor Stains & Wall Damage May Be Traced to Chimney Leaks
Our photos above show a rather obvious water leak from the inside of a chimney flue onto the wall and floor below. But other chimney leak clues that are less obvious may be present indoors too.
Illustrated in our photos below is the importance of looking closely at walls above a fireplace and where a chimney passes through a building. Especially in poorly-lit rooms, the importance of proper use and aiming of a good flashlight become quite evident. Our photographs show the discovery of water damage and efflorescence traced to a leaky chimney on a historic home in Newburgh, NY.
Fireplace Stains May Indicate Chimney Leaks & Damage
At left our fireplace photograph illustrates another spot to detect water leakage down the interior of a chimney structure or chimney flue.
Note the white efflorescence and stains on the back and sides of the fire box.
Without further investigation we can't be sure if the problem is a rain cap or a chimney cap seal or perhaps (less often) even a chimney to roof flashing problem.
The flue needs to be inspected for safety and the chimney leak found and repaired.
At left the odd installation of chimney flue tiles run up through the middle of a fireplace ought to be a red flag to inspect closely for amateur and probably unsafe workmanship.
Watch out for
At left we show white stains and rust atop a zero-clearance fireplace insert and more rust down the side of the metal flue itself.
You won't normally have access to inspect the interior of a finished fireplace insert.
But you should always be very alert for signs of leaks and rust damage to the unit, including inspecting inside the hearth as well as from the basement or crawl space below.
Rust damaged heating equipment may be unsafe.
Stains and leak damage to a chimney may be visible in the attic
Brown or black oozing stains may appear on both masonry chimney and metal chimney exteriors, though if the metal chimney was properly assembled such leaks onto the metal chimney exterior surface are unlikely.
The brick chimney at left has both white and black stains as well as what looks like a vertical crack along its right side - this chimney maybe unsafe and needs prompt investigation.
The brick chimney with brown-black stains oozing from between the next chimney's mortar joints (photo at below left) tells us that water has been entering the chimney flue (missing rain cap or improper chimney top cap/crown seal or other chimney leaks).
These brown chimney stains may be still more significant: they may indicate that the chimney flue is unlined and possibly unsound and unsafe.
The pair of photos above teach several additional important chimney inspection lessons:
These black stains on a masonry or metal chimney are not mold. (Mold prefers to grow on organic materials.
Stains, cracks, evidence of chimney leaks & damage may be visible in the basement
The stains down the side of the white-painted concrete block chimney shown at left were traced to foundation leaks - we found horizontal cracking in the concrete block foundation wall and more water stains in this same area.
The stains also led to observation of the cracking, damaged chimney base also visible in our photo at left.
Watch out: cracks in a masonry chimney mean movement, risk of hidden internal damage to the chimney flue, and potentially fatal flue gas leaks or to a building fire.
Brown or black oozing stains may appear near the bottom of a chimney below a thimble (where the flue vent connector inserts into the chimney) or around or below a chimney cleanout door (photo at left).
If you see marks such as those shown in our photo you will want to find the source of leaks into the chimney, such as a bad rain cap, chimney cap, roof flashing, or even ground water entering the chimney base - all problems that need be corrected.
See CHIMNEY CLEANOUT DOORS for more examples of signs of leakage into the chimney, and see CHIMNEY CAP & CROWN and also CHIMNEY FLASHING Mistakes & Leaks for other leak points commonly found on masonry and some metal chimneys and flues.
Watch out: leaks into a chimney risk having damaged the chimney, flue vent connector, or heating appliance - making any of these dangerous, risking chimney damage, flue gas leaks, or a building fire.
Green link shows where you are in this article series.
Frequently Asked Questions (FAQs) about diagnosing indoor stains on or caused by chimneys
Questions or comments about stains indoors traced to chimney leaks or defects..
Ask a Question or Enter Search Terms in the InspectApedia search box just below.
Technical Reviewers & References
Related Topics, found near the top of this page suggest articles closely related to this one.