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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 TYPES & MATERIALS
DIRECT VENTS / SIDE WALL VENTS
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, COAL STOVES & FIREPLACES
Angled chimneys & sloped flues: this article explains the hazards of angled or sloped masonry or metal chimneys and chimney flues.
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.
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This article series describes chimney defects and hazards that can be observed from on-roof access, including damage to a masonry chimney top, antennas mounted on chimneys, and angled chimney flue hazards.
Our photo at page top shows a chimney that was angled severely beginning at the attic floor - look there for cracks that may have opened, forming a fire and gas hazard.
Offset or angled chimney flues are found in both masonry and metal chimney installations.
Especially where multiple flues are routed inside of a single large masonry chimney or inside of a single wood-framed chimney chase, it should not be a surprise to discover that one or more of the appliances venting into one or more of the flues has to send its gases up at an angle to reach the final vertical section of flue in the chimney.
Look for these clues that may indicate angled chimney flues that deserve further inspection:
Just as we reported that a clay tile lined chimney would be difficult to clean due to projecting concrete between vertically-stacked clay chimney tiles, clay tiles need to be cut properly when constructing an angled chimney such as the one shown in Carson Dunlop's sketch.
The sketches shown at left shows the concern with proper miter joints in a sloping masonry chimney flue.
[Click to enlarge any image]
Only the bottom design, showing that the clay chimney tile was cut on an angle, is correct.
The top two designs risk both cleaning difficulties and also water, smoke, soot,or creosote leaks into the chimney structure.
The next Carson Dunlop sketch at left shows that a masonry flue is limited to 30 deg. offset, or in some jurisdictions, 45 degrees of offset while a metal flue may, in some areas, be permitted to slope to 60 degrees of offset.
In sum, concerns about angled or sloping chimneys and chimney flues include:
Support Rules for Sloped Chimneys & Elbows in Metal Chimneys & Flues
If elbows are used in the chimney the slope cannot be less than 30 degrees, and the sloping segment of the chimney above each elbow must be supported by straps or other means specified by the chimney manufacturer.
Continue reading at CHIMNEY LEANING, SEPARATION, MOVEMENT or select a topic from the More Reading links shown below.
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Frequently Asked Questions (FAQs)
Question: purpose of the sloped Colonial chimney
(Apr 20, 2012) George Miller said:
What was the purpose of the sloped Colonial chimney. I was told that it was sloped to prevent rain from putting out the fire. Is this true?
Colonial masons often brought a more central chimney straight up into the attic floor then built the chimney on an angle specifically to cause it to exit the roof at the roof's highest point - the ridge. The reasons for that decision were both cosmetic or aesthetic and possibly for improved fire safety and in some conditions improved draft too.
Rain falling into a chimney can cause ugly creosote runs and drips into the fireplace - an event addressed by a chimney cap, not by a sloped flue.
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