InspectAPedia ® Home

CHIMNEY INSPECTION DIAGNOSIS REPAIR

BACKDRAFTING HEATING EQUIPMENT

CARBON MONOXIDE - CO
CHIMNEY CAP & CROWN
CHIMNEY CLEANING PROCEDURES
CHIMNEY COMPONENT DEFINITIONS
CHIMNEY CRACK DETECTION & DIAGNOSIS
CHIMNEY DRAFT & PERFORMANCE
CHIMNEY FIRE ACTION / PREVENTION
CHIMNEY HEIGHT & CLEARANCE CODE
CHIMNEY INSPECTION, FLUE INTERIOR
CHIMNEY LEANING, SEPARATION, MOVEMENT
CHIMNEY REPAIR METHODS
CHIMNEY STAINS & LEAKS
CHIMNEY SWEEPS
CHIMNEY TYPES & MATERIALS
COAL STOVE OPERATION & SAFETY

DIRECT VENTS / SIDE WALL VENTS
DRAFT HOOD, GAS HEATER
DRAFT REGULATOR, DAMPER, BOOSTER

FIRE CLEARANCES INDOORS
FIREPLACES & HEARTHS
FLUE VENT CONNECTORS

MASONRY CHIMNEY GUIDE
METAL CHIMNEYS & FLUES

SAFETY RECALLS CHIMNEYS VENTS HEATERS
SOOT AT CHIMNEY TOP
STAIN DIAGNOSIS on BUILDING EXTERIORS

WOOD-OIL COMBINATION HEATERS

More Information

Stains indicate chimney leaks and damage (C) Daniel Friedman Chimney-Caused Stains on Building Interior Surfaces
Chimney creosote, efflorescence, soot, water leak stain on ceilings, walls, floors
     


InspectAPedia tolerates no conflicts of interest. We have no relationship with advertisers, products, or services discussed at this website.

How to diagnose indoor stains at chimneys or caused by chimney problems.

What causes stains in, on or around chimneys and what do these stains mean? Unsafe chimney conditions may be indicated by leaks, stains, or crud seeping out of a chimney connection or a chimney crack. We point out that stains at chimneys are usually more than cosmetic and that they may indicate serious safety hazards as well as chimney functional problems.

This article series 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.

Green links show where you are. © Copyright 2015 InspectApedia.com, All Rights Reserved.

Significance of Stains on a Chimney Exterior Surface: Creosote, soot, water

Water and Chimney Leaks Lead to Damage

Stains indicate chimney leaks and damage (C) Daniel Friedman Stains indicate chimney leaks and damage (C) Daniel Friedman

The pair of photos above teach several important chimney inspection lessons:

  1. It is important to notice stains on a chimney exterior surface: stains from water, creosote, or soot leaking out of a chimney such as in this attic. The stains tell us that water has been entering the flue, raising an alert for frost damage. This is not just a cosmetic concern: flue gases and sparks can enter the building.
  2. Water leaking into a chimney increases the chance of damage to the chimney flue or chimney structure.
  3. Inspection distractions: Don't let one observation at a chimney distract you or convince you that further up-close inspection is not needed. When we crowded in around the corner to see the side of this chimney we found the gaping hole in the photo at right.
  4. Looking into a chimney through any opening that presents itself an tell us immediately whether or not the flue is lined and what is the thickness (and thus some information about safety) of the chimney walls. Finding a chimney liner does not assure that the whole flue is lined and in good condition, but finding no chimney flue liner and a single wythe brick construction in any location tells us something important about the chimney safety.

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.

Water and Chimney Leaks Lead to Damage that may show up indoors on walls

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

Chimney leak stains at the cleanout door (C) Daniel FriedmanChimney leak stains at the cleanout door (C) Daniel Friedman

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.

Chimney leak stains (C) Daniel FriedmanChimney leak stains (C) Daniel Friedman

Fireplace Stains May Indicate Chimney Leaks & Damage

Fireplace leak stains (C) Daniel Friedman

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.


 

...

Fireplace leak stains (C) Daniel FriedmanAt 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

  • improper sharing of a single flue between the fireplace and a basement heating appliance - unsafe conditions
  • leaks at the chimney top - hidden chimney damage, possibly heater damage too
  • improper and unsafe chimney construction
  • more work on this home performed by the same do-it-yourself'ers
...

Fireplace leak stains (C) Daniel Friedman

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

Brick chimney with stains and cracking (C) Daniel Friedman

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.


Stains indicate chimney leaks and damage (C) Daniel Friedman Stains indicate chimney leaks and damage (C) Daniel Friedman

The pair of photos above teach several additional important chimney inspection lessons:

  1. It is important to notice stains on a chimney exterior surface: stains from water, creosote, or soot leaking out of a chimney such as in this attic. The stains tell us that water has been entering the flue, raising an alert for frost damage. This is not just a cosmetic concern: flue gases and sparks can enter the building.
  2. Water leaking into a chimney increases the chance of damage to the chimney flue or chimney structure.
  3. Inspection distractions: Don't let one observation at a chimney distract you or convince you that further up-close inspection is not needed. When we crowded in around the corner to see the side of this chimney we found the gaping hole in the photo at right.
  4. Looking into a chimney through any opening that presents itself an tell us immediately whether or not the flue is lined and what is the thickness (and thus some information about safety) of the chimney walls. Finding a chimney liner does not assure that the whole flue is lined and in good condition, but finding no chimney flue liner and a single wythe brick construction in any location tells us something important about the chimney safety.

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

Chimney cracks, damage, ground water leaks (C) Daniel Friedman

 

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.

 

 

 

...


Chimney leak stains at the cleanout door (C) Daniel Friedman

 

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.

Also 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.

 

 

Continue reading at CHIMNEY STAINS & LEAKS or select a topic from the More Reading links shown below.

Or see EFFLORESCENCE SALTS & WHITE DEPOSITS

Suggested citation for this web page

CHIMNEY STAINS, INDOORS at InspectApedia.com - online encyclopedia of building & environmental inspection, testing, diagnosis, repair, & problem prevention advice.

More Reading

Green link shows where you are in this article series.

...




Frequently Asked Questions (FAQs)

Click to Show or Hide FAQs

Ask a Question or Search InspectApedia

Use the "Click to Show or Hide FAQs" link just above to see recently-posted questions, comments, replies, try the search box just below, or if you prefer, post a question or comment in the Comments box below and we will respond promptly.

Search the InspectApedia website

HTML Comment Box is loading comments...

Technical Reviewers & References

Publisher's Google+ Page by Daniel Friedman

Click to Show or Hide Citations & References