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 Mobile ViewCHIMNEY INSPECTION DIAGNOSIS REPAIR Abandoned Chimneys - Indoor Inspection Abandoned Chimneys: Outdoors Angled Chimney Flues ARCHITECTURE & BUILDING COMPONENT ID Attic Chimney Inspection BACKDRAFTING HEATING EQUIPMENT BAROMETRIC DAMPERS Blocked Chimney Flues Bracket Chimney Collapse & Fire Risks B-Vent Chimneys B-Vent Clearances Table CARBON DIOXIDE - CO2 CARBON MONOXIDE - CO CHIMNEY INSPECTION & REPAIR GUIDE Chimney Cap & Crown Inspection Missing Chimney Rain Cap Damaged Masonry Chimney Cap or Crown Masonry Chimney Top Damage Separation of Chimney Flues - Chimney Top Soot at the Chimney Top UNLINED FLUE INSPECTIONS CHIMNEY CHASE Construction & Defects Chimney Cleaning Advice, Procedures Chimney Cleaning Fraud Warning Chimney Cleanout Doors Chimney Components Definitions Chimney Crack & Collapse Risks, Repairs Articles on Collapsing Chimneys Bracing for Masonry Chimneys Bracing for Masonry Chimneys, Lateral Bracing for Metal Chimneys Bracket Chimney Collapse & Fire Risks Earthquake Chimney Collapse Dangers Chimney Crack Detection & Diagnosis Chimney Leaning, Separation, Movement-Outdoors Cracked Brick Chimney Sides Cracked Concrete Block Chimneys Curved Brick Chimneys Split Openings in Brick & Chimney Collapse Chimney Draft & Performance Draft: Thermal Performance of Chimneys CHIMNEY FIRE ACTION / PREVENTION Chimney Flashing Mistakes & Leaks CHIMNEY HEIGHT & CLEARANCE CODE Adjacent Metal Chimney Separation B-Vent Clearances Table Chimney Too Short Chimney Height Extensions Chimney Height for Types L & Type B Vents Fire Clearances for Masonry Chimneys Fire Clearances for Metal Chimneys FIRE CLEARANCES, Single-Wall Metal Flues Masonry Chimney Roof Clearance Wood burning Fireplace Roof Clearance Chimney Height Extensions Chimney Inspection Checklist Chimney Inspection: Flue Interiors ChimScan: Inspecting Flues by Cameras Chimney Inspection Indoor Procedures Chimney Inspection Outdoors From Ground Chimney Inspection Outdoors at Rooftop Angled Chimney Flues Blocked Chimney Flues Chimney Cap & Crown Inspection Missing Chimney Rain Cap Damaged Masonry Chimney Cap or Crown Separation of Chimney Flues - Chimney Top Chimney Crack Detection & Diagnosis Chimney Exterior Spalling Chimney Flashing Mistakes & Leaks Chimney Shoulder Leaks Flue Tile Damage in Chimneys Masonry Chimney Top Damage Soot at the Chimney Top UNLINED FLUE INSPECTIONS Chimney Leaning, Separation, Movement Chimney Movement, Indoor Clues Chimney Movement, Causes Chimney Movement, Ongoing vs Static Chimney Footing Defective / Missing Foundation Support for Masonry Chimneys Leaning Chimney Repair Methods Chimney Repair Fraud Warning Chimney Repair Methods Bracing for Masonry Chimneys Bracing for Metal Chimneys Bracing for Masonry Chimneys, Lateral Chimney Height Extensions Chimney Top & Clay Flue Tile Repairs Connecting Metal Chimney Sections Damaged Chimney flues: cracks, holes, spalling Draft Inducer Fans Leaning Chimney Repair Methods Re-Lining Choices for Masonry Chimneys Replacement Components for Metal Chimneys Chimney Safety - CPSC Alert Chimney Shoulder Leaks Chimney Spalling, Exterior Chimney Sweeps Chimney Types & Materials CO2 TOXICITY COALSTOVE SAFETY COMBUSTION AIR DEFECTS COMBUSTION AIR for TIGHT buildings COMBUSTION GASES & PARTICLE HAZARDS COMBUSTION PRODUCTS & IAQ COMPLETE COMBUSTION, Stoichiometric CREOSOTE FIRE HAZARDS Dead End Chimney Flue Hazards Definitions of Chimney Types & Parts DIRECT VENTS / SIDE WALL VENTS DRAFT HOODS - gas fired DRAFT MEASUREMENT, CHIMNEYS & FLUES DRAFT REGULATORS, DAMPERS, BOOSTERS EFFLORESCENCE, Salts & White / Brown Deposits EMERGENCY RESPONSE, IAQ, GAS, MOLD FIRE CLEARANCES INDOORS Fire Clearances for Masonry Chimneys Fire Clearances for Metal Chimneys FIRE CLEARANCES, Single-Wall Metal Flues FIREPLACES & HEARTHS Fire stopping at Chimney Passage Through Floors FLAME COLOR, BLUE vs YELLOW COMBUSTION FLUE SIZE SPECIFICATIONS Flue Separation Requirements Flue Tile Damage in Chimneys Flue Vent Connectors - Boilers, Furnaces Fuel Changes for Heating ApplianceS HEATING COST FUEL & BTU Cost Table HEATING INSPECTIONS HOME HEATING SAFETY HEATING SYSTEMS INDOOR AIR EMERGENCY RESPONSE Lennox SAFETY WARNING Metal Chimneys & Flues Moisture / Frost Damaged Chimney Nanomaterials Hazards NOISE / SOUND DIAGNOSIS & CURE ODORS & SMELLS DIAGNOSIS & CURE ODORS FROM HEATING SYSTEMS OIL HEAT SAFETY INSPECTIONS PLASTIC HEATER VENTS Safety Recalls, Chimneys, Vents, Heaters Shared Chimney & Shared Flue Hazards STAIN DIAGNOSIS on BUILDING EXTERIORS STAINS on/near CHIMNEYS Three-Sided Chimneys: Problems Transite Pipe Chimneys & FlueS UNLINED FLUE INSPECTIONS WOOD, COAL STOVES & FIREPLACES WOOD STOVE SAFETY More Information |
This article describes chimney top repairs for masonry chimneys and clay flue tiles, work performed at or from the rooftop. This website provides 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. InspectAPedia tolerates no conflicts of interest. We have no relationship with advertisers nor with topics or services discussed at this website.© Copyright 2012 InspectAPedia.com, All Rights Reserved. Information Accuracy & Bias Pledge is at below-left. 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. Repair of Damaged Clay Chimney Flue Liners at the RooftopDetermine the Extent of Chimney Damage and the Safety of the Entire Chimney Flue
Our photo above shows an unsafe chimney that was still in active use. Notice those missing bricks and lost mortar? Damaged chimney top masonry such as missing bricks and a missing chimney cap were easily spotted from ground level, raising a critical concern for the fire and gas-leak safety of the clay flue tiles lining this chimney. At the front left corner of the clay chimney flue tile you can see our pen inserted into an opening between the chimney flue tile and the (damaged) surrounding brick and concrete chimney structure - water entering the chimney structure at this location risks freeze damage to the chimney flue itself, resulting in potentially very dangerous conditions. First, you will want to be absolutely sure that the chimney damage, whether to the ceramic clay flue liner or to the surrounding masonry or both, is limited to the upper, visible, accessible part of the chimney. Our chimney clay flue tile liner damage photos above show enough wear and cracking (above left) and opening between clay flue tile liner sections (above right) that further inspection and repair by a chimney professional is warranted. Other chimney damage lower in the chimney itself as it passes through or alongside the building could be very dangerous, even fatal if carbon monoxide or other flue gases leak into the building or if sparks cause a fire.
Our photos above show damage to the chimney clay flue tiles near the chimney top, with multiple cracks in the clay flue liner (above left), and severe spalling in the clay flue tile liner (above right) -these are two different chimneys. Both need repair. The right hand chimney (above right) may need a complete re-lining while the chimney at above left might be damaged only above the roof line, making roof top repair a reasonable approach. We suggest that you hire a professional chimney sweep who can examine the entire chimney flue. Most chimney sweeps also offer repair services, and can suggest what repairs are needed and give alternatives for the particular chimney and flue on your building. Reline the Chimney versus Repairs Just at the Chimney Top
Some chimney repair contractors will want to reline the whole chimney flue - an approach that is often safe, quick, easy, and profitable. But this approach may be inappropriate if the damage is just due to weather at the chimney top and the rest of the flue is intact and safe. Water leaking between the flue liner and the masonry surround is also a very common cause of water and frost damage at the chimney top. Most often we see spalling flue liners and loose or damaged bricks or concrete block around a chimney top caused in large part by failure to protect the chimney to from the weather; lack of an allowance for thermal movement among chimney parts, especially the liner and the surrounding masonry,can also crack and break the flue liner, especially on the above-roof portion where the chimney is in northern climates exposed to coldest temperatures. Potentially, damage to the masonry chimney structure as well as to its clay flue tile liner can occur also inside a freezing attic space. If the damage is just at the top of the chimney and its masonry flue liner, repairs can usually be completed entirely from outside, working from the rooftop. (Be sure the mason performing the repairs protects the surrounding roof surface from damage lest your chimney repair be followed by roof leaks.) Other Chimney Top Repairs for Damaged Flue Liners or Surrounding Masonry
A better approach and the one used by most chimney repair masons who are not going to simply reline the flue, is to remove all of the damaged materials down to sound chimney flue liner and brick or block, then rebuild with new clay flue liner and brick (or block), adding an appropriate chimney cap and top seal. Using solid masonry between the clay liner and the surrounding masonry at the chimney top is a common practice (photo at left), and having inspected quite a few chimney tops, we can't say that every chimney built this way fails, but it is not the best practice and is not recommended by experts.
Other problems at this chimney top include the termination of both flues at the same height, and the absence of any rain cap. Using a fire-safe flexible caulk at that joint will reduce the chances of cracking due to temperature differences. Carson Dunlop's sketch ( above-left) show some details of good chimney cap construction. The object of these details is to avoid water and frost damage to the flue or to the chimney itself. See Chimney Inspection From Outside - Rooftop for these chimney top inspection and final repair and sealing details.
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