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STRUCTURAL INSPECTIONS & DEFECTS
CARBON MONOXIDE
CHIMNEY INSPECTION DIAGNOSIS REPAIR
CHIMNEY INSPECTION & REPAIR GUIDE
Chimneys Cleaning Advice, Procedures
Chimney Cleanout Doors
Chimney Crack & Collapse Risks, Repairs
Articles on Collapsing Chimneys
Bracket Chimney Collapse & Fire Risks
Chimney Movement - Outdoor Evidence
Chimney Movement - Indoor Evidence
Chimney Movement - Ongoing vs Static
Chimney Crack Detection & Diagnosis
Cracked Concrete Block Chimneys
Curved Brick Chimneys
Earthquake Chimney Collapse Dangers
Leaning Chimney Repair Methods
Split Openings in Brick & Chimney Collapse
Chimney Draft & Performance
Chimney Inspection Checklist
Chimney Inspection Indoor Procedures
Attic Chimney Inspection
Chimney Inspection Outdoors From Ground
Chimney Crack Detection & Diagnosis
Chimney Inspection Outdoors From Ground
Chimney Height & Clearance
Chimney Inspection Outdoors at Rooftop
Chimney Cap & Crown Inspection
Masonry Chimney Top Damage
Chimney Flashing Mistakes & Leaks
Chimney Crack Detection & Diagnosis
Chimney Shoulder Leaks
Chimney Exterior Spalling
Chimney Repairs
Connecting Metal Chimney Sections
Damaged Chimney flues: cracks, holes, spalling
Re-Lining Choices for Masonry Chimneys
Replacement Components for Metal Chimneys
Chimney Types & Materials
Masonry & Clay Tile Chimneys
Factory Built Chimneys
Single-Wall Metal Pipe Chimneys Vents
Double-Wall Metal, Type B & Type L Chimneys
High Temperature Plastic Chimneys & Vents
Device Categories vs. Chimney Requirements
New Vent Requirements
Draft Hood Appliances
Mid-Efficiency Heating Appliances
High Efficiency Heating Appliances
CO2 TOXICITY
COALSTOVE SAFETY
Dead End Chimney Flue Hazards
Definitions of Chimney Types & Parts
DRAFT HOODS - gas fired
DRAFT REGULATORS - barometric dampers
Fire Clearances for Masonry Chimneys
Fire Clearances for Metal Chimneys
Fire Clearances, Single-Wall Metal Flues
Chimney Height & Clearance
Reduction in Fire Clearance - Heat Shields
Single Wall Metal Flues - Oil fired heaters
Single Wall Metal Pipe Flues - Gas heaters
Wood & Coal Stove Flues
Fire Clearance Safety Hazards, other
Fireplace Damage & Unsafe Hearths - Settlement
Creosote Deposits - Fire Hazard
Dead End Flues - Dead Base Chimney Hazards
Fire stopping at Chimney Passage Through Floors
Fireplace Inserts
Inaccessible Connections Fireplace or Woodstove
Flue Sizing of Chimneys
Fire Stopping Between Floors
Flue Vent Connectors - Boilers, Furnaces
Blocked Chimney at the Flue Vent Connector
Dead End Chimney Flue Hazards
Extended Too Far into Chimney
Joint Connections - Single Wall Metal Flues
Length Limits for a Flue Vent Connector
Loose, Leaky, Not Sealed, Flue Vent Connector
Plastic Heater Vents
Plastic Vents Goodman HTPV Recall
Rusted Metal Flue Vent Connectors
Slope, Proper Flue Vent Connector
Chimney Inspection: Flue Interiors
Flue Interior Inspection Methods
Barometric Damper view of Flue
Chimney Thimble Requirements
Chimney Thimble Damage
Cleanout Door view of Flue
Masonry Fragments & Debris at the Cleanout
ChimScan: Inspecting Flues by Cameras
Fuel Changes for Heating Appliances
Metal Chimneys & Flues
Bracing for Metal Chimneys
Class A Chimneys, MetalBestos™
Connecting Metal Chimney Sections
Continuous metal chimneys
Definitions of Chimney Types & Parts
Fire Clearances for Metal Chimneys
Height required for L Vents & B Vents
Indoor Hazards, Metal Chimney & Vent
Manufactured Chimneys
Offset from Vertical in Chimneys, excessive
Replacement Components for Metal Chimneys
Single-Wall Metal Vents & Chimneys
Super Chimneys, 629 Chimneys
Triple-Wall Metal Fireplace Chimneys
Type B-Vents
Type L Vents
Wet time & Corrosion in Chimneys, Vents
Wood Framed Chimney Chases
Shared Chimney & Shared Flue Hazards
Shared Chimney Flue Examples
Exceptions: Shared Flues Permitted?
Wood & Oil Fired Heaters
Two Gas Fired Appliances Vent in One Flue
Multiple Fireplaces Sharing One Flue
HEATING INSPECTIONS
HOME HEATING SAFETY
Lennox WARNING
Moisture Problems Damage Chimneys
OIL HEAT SAFETY INSPECTIONS
PLASTIC HEATER VENTS
PLASTIC VENTS Goodman HTPV RECALL
Transite Pipe Chimneys & Flues
UNLINED FLUE INSPECTIONS
Weil McLain RECALL
Wood Burning Heaters Fireplaces Stoves
Coalstove Safety
Fire Clearance Safety Hazards
Fire stopping at Chimney Passage Through Floors
HEATING COST FUEL & BTU Cost Table
Woodstove Safety
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Chimney & Fireplace Settlement, Cracks, Collapse: Fire Hazard Diagnosis & Repair
ChimAPedia ©
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- Fireplace damage from chimney or fireplace settlement or movement may be a fire or gas hazard in a building
- Photo examples of cracks in on and around masonry fireplaces and a guide to their cause and remedy
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This article describes cracks and gaps that appear at masonry fireplaces due to chimney or fireplace settlement or movement. We explain why these gaps form a dangerous fire hazard and we suggest what to do about them.
Do not use a fireplace that is in any doubt about safety before it has been inspected by a professional.
Our photo (above) shows a fireplace mantel that collapsed and fell into the room. Smoke stains revealed on the brick might point to a chimney draft problem too.
The fireplace schematic (at left) shows the basic components of a masonry fireplace and their names. This drawing is obsolete in that it is missing a combustion air supply for the fireplace.
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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. As with most inspection and safety topics, this material may be incomplete.
© Copyright 2008 Daniel Friedman, All Rights Reserved. Information Accuracy & Bias Pledge is at below-left. Use links at the left of each page to navigate this document or to view other topics at this website. Green links show where you are in our document or website.
Fireplace Damage and Unsafe Hearths due to Chimney or Fireplace Settlement
 Carson Dunlop's sketch shows a cross section of the basic components of a chimney where a fireplace is installed. (Click the image at left or photos below to enlarge them).
Beginning with the outside inspection of the chimneys and structure, and continuing indoors, we check for a wide range of possible chimney hazards. Among these are issues surrounding chimney movement, settlement, or separation from the building.
Too often we discover that a building owner was aware that a chimney has moved, s/he has patched the gap between the chimney and the building, but s/he has not realized that the movement causes cracks and gaps inside the chimney or fireplace which are very dangerous.
Below we provide three photographs showing how a fireplace can become a fire hazard due to chimney settlement or inadequate support of the fireplace itself.
We start with a look at the fireplace hearth for evidence of movement. |
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 In an easy-to-spot case of movement and separation between a fireplace hearth and the building floor take a look at the white caulk installed in an open crack between the hearth face and the floor in our photo (left).
A bit more investigating was needed to determine whether the floor was sagging away from a stable masonry fireplace and chimney or whether the chimney and entire firebox were leaning away from the building.
In the next case, just below, the gaps and cracks made it obvious that the chimney and fireplace were tipping away from the building in a dangerous condition. |
First at above left we see a gap that has opened up between the fireplace floor and the hearth (above-left). Sparks may fall into this space, causing a building fire.
Second (above right) our photo shows a crack between the face of the fireplace and the fireplace box itself. We don't know without more analysis whether the brick facing has fallen away from a sound and safe fireplace or whether the fireplace has moved away from the facing.
Our third fireplace damage photograph (left) is the final nail in the coffin of this unfortunate fireplace.
A gap has opened in the fireplace below the chimney where the damper was cemented in place. There has been substantial movement of the fireplace itself (and probably the chimney too) - this is an unsafe fireplace that should not be used.
But not using the fireplace is not enough to be sure this home doesn't have another fire or glue gas hazard.
If a fireplace and chimney have settled and thus have become unsafe, we need to determine right away if any other building appliances such as a boiler, furnace, water heater, or woodstove are using other flues in the same chimney.
If the chimney has multiple users it is unsafe for all of them.
Also see these articles on chimney collapse hazards:
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Adding Support Below a Settling Fireplace Hearth
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 You may find a temporary supporting column such as this Lally column which was placed below a sagging fireplace.
Some diagnosis of just what caused settling or movement in a hearth is critical.
A gap appearing between the hearth and the edge of the firebox might be due to inadequate hearth support - not such an ugly repair - or it might be due to settlement of the entire chimney and fire chamber away from the building - a major repair and a dangerous condition.
See Chimney Crack & Collapse Risks, Repairs.
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Fireplace Hearth Size Requirements
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Our photo (left) shows a burned wooden floor in front of a fireplace hearth.
Hearth dimensions: A fireplace hearth should extend at least 16" (M.I.A.) past the front edge of the fireplace and at least 8" beyond each side of the fireplace opening.
Where the fireplace opening is 6 sq.ft. or bigger the front extension needs to be increased to at least 20" and the side extensions to at least 12" beyond the fireplace front.
The hearth for a masonry fireplace needs to be made of a brick, concrete, stone, or other (approved, listed) non-combustible material. The hearth slab needs to be at least 4" in thickness, it has to be supported by noncombustible materials or able to carry its own weight.
The "cribbing" or wood forms used to support a poured concrete hearth should be removed after construction is completed. We often find this wood material left in place - where sparks falling through a crack or gap can start a fire.
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Carpeting too Close to Fireplace
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Carpets and other combustibles need to be kept away from the fireplace front and hearth.
Often where the hearth sits at floor level we find that someone has installed carpeting right up to the fireplace - a fire hazard as our client is remarking in our photo (left).
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Fireplace Damper Trouble Inspection, Diagnosis, Repair
Stuffing a pillow into the chimney throat of a fireplace (above left) might slow the loss of warm air from a home, but it's a dangerous substitute for a missing or broken fireplace damper. What if someone lights a fire without noticing this stuffing?
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 A normal cast iron fireplace damper is shown in closed position in our photo at above right. Closing the damper when the fireplace is not in use will make a significant reduction in heat loss from most buildings. \
Inspect fireplaces for a working damper. Where a steel insert fireplace is installed, inspect the upper portions of the fireplace at the chimney throat with great care. A rusted-out steel fireplace inset will be unsafe, wont' work properly, and will be costly to replace.
Our photograph (left) shows a steel fireplace insert at an incomplete fireplace installation in a basement. What about that plywood "face" nailed around the steel fire chamber? |
Use links just below or at the left of each page to navigate this document or to view other topics at this website. Green links show where you are in our document or website.
CHIMNEY INSPECTION DIAGNOSIS REPAIR
CHIMNEY INSPECTION & REPAIR GUIDE
CHIMNEY INSPECTION DIAGNOSIS REPAIR
Chimneys Cleaning Advice, Procedures
Chimney Cleanout Doors
Chimney Crack & Collapse Risks, Repairs
Chimney Draft & Performance
Chimney Inspection Checklist
Chimney Inspection Indoor Procedures
Attic Chimney Inspection
Chimney Inspection Outdoors From Ground
Chimney Crack Detection & Diagnosis
Chimney Inspection Outdoors From Ground
Chimney Height & Clearance
Chimney Inspection Outdoors at Rooftop
Chimney Cap & Crown Inspection
Chimney Types & Materials
Chimney Cleanout Doors
Fire Clearances for Masonry Chimneys
Fire Clearances for Metal Chimneys
Fire Clearances, Single-Wall Metal Flues
Flue Sizing of Chimneys
Fire Stopping Between Floors
Flue Vent Connectors - Boilers, Furnaces
Chimney Inspection: Flue Interiors
Metal Chimneys & Flues
Shared Chimney & Shared Flue Hazards
Fireplace Damage & Unsafe Hearths - Settlement
Creosote Deposits - Fire Hazard
Dead End Flues - Dead Base Chimney Hazards
Fire stopping at Chimney Passage Through Floors
Fireplace Inserts
Inaccessible Connections Fireplace or Woodstove
Moisture Problems Damage Chimneys
Wood Burning Heaters Fireplaces Stoves
Technical Reviewers & References
Particular thanks are due to experts and also consumers who read these articles and suggest corrections, changes, and additions to
the material. Content suggestions, technical corrections and content critique are invited for any of the content at our website.
- Daniel Friedman - principal author/editor of the InspectAPedia TM Website
- Thanks to Alan Carson and Bob Dunlop, Carson Dunlop, Associates, Toronto, for permission to use illustrations from their publication, The Illustrated Home which illustrates construction details and building components. Carson Dunlop provides home inspection education, publications, report writing materials, and home inspection services. Alan Carson is a past president of ASHI, the American Society of Home Inspectors.
- Arlene Puentes, an ASHI member and a licensed home inspector in Kingston, NY, and has served on ASHI national committees as well as HVASHI Chapter President. Ms. Puentes can be contacted at ap@octoberhome.com
- Roger Hankey is principal of Hankey and Brown home inspectors, Eden Prairie, MN, technical review by Roger Hankey, prior chairman, Standards Committee, American Society of Home Inspectors - ASHI. 952 829-0044 - hankeyandbrown.com
- Chimney Building Codes and Chimney, Flue, and Appliance Venting Standards
- NFPA #211-3.1 1988 -
Specific to chimneys, fireplaces, vents and solid fuel burning appliances.
- NFPA # 54-7.1 1992 -
Specific to venting of equipment with fan-assisted combustion systems.
- GAMA -
Gas Appliance Manufacturers' Association has prepared venting tables for
Category I draft hood equipped central furnaces as well as fan-assisted
combustion system central furnaces.
- National Fuel Gas Code, an American National Standard, 4th ed. 1988 (newer edition is available) Secretariats, American Gas Association (AGA), 1515 Wilson Blvd., Arlington VA22209, and National Fire Protection Association (NFPA), Batterymarch Park, Quincy MA 02269. ANSI Z223.1-1988 - NFPA 54-1988. WARNING: be sure to check clearances and other safety guidelines in the latest edition of these standards.
- Fire Inspector Guidebook, A Correlation of Fire Safety Requirements Contained in the 1987 BOCA National Codes, (newer edition available), Building Officials and Code Administrators International, Inc. (BOCA), Country Club HIlls, IL 60478 312-799-2300 4th ed. Note: this document is reissued every four years. Be sure to obtain the latest edition.
- Masonry Fireplace and Chimney Handbook, 2nd Ed. M.I.A. Masonry Institute of America, Los Angeles, CA 213-388-0472 prepared to include requirements of the 1994 UBC and other codes.
- Uniform Mechanical Code - UMC 1991, Sec 913 (a.) Masonry Chimneys,
refers to Chapters 23, 29, and 37 of the Building Code.
- New York 1984 Uniform Fire
Prevention and Building Code, Article 10, Heating, Ventilating, and Air Conditioning Requirements
- New York 1979 Uniform Fire Prevention & Building Code, The "requirement" for 8" of solid masonry OR for use of a
flue liner was listed in the One and Two Family Dwelling Code for New
York, in 1979, in Chapter 9, Chimneys and Fireplaces, New York 1979
Building and Fire Prevention Code:
- "Top Ten Chimney (and related) Problems Encountered by One Chimney Sweep," Hudson Valley ASHI education seminar, 3 January 2000, contributed by Bob Hansen, ASHI
- Chimney Inspection Checklist, Carson Dunlop, Associates, Toronto, Ontario
- "Rooftop View Turns to Darkness," Martine Costello, Josh Kovner, New Haven Register, 12 May 1992 p. 11: Catherine Murphy was sunning on a building roof when a chimney collapsed; she fell into and was trapped inside the chimney until rescued by emergency workers.
- "Chimneys and Vents," Mark J. Reinmiller, P.E., ASHI Technical Journal, Vol. 1 No. 2 July 1991 p. 34-38.
- "Chimney Inspection Procedures & Codes," Donald V. Cohen was to be published in the first volume of the 1994 ASHI Technical Journal by D. Friedman, then editor/publisher of that publication. The production of the ASHI Technical Journal and future editions was cancelled by ASHI President Patrick Porzio. Some of the content of Mr. Cohen's original submission has been included in this more complete chimney inspection article: InspectAPedia.com/chimneys/Chimney_Inspection.htm. Copies of earlier editions of the ASHI Technical Journal are available from ASHI, the American Society of Home Inspectors.
- Natural Gas Weekly Update: http://tonto.eia.doe.gov/oog/info/ngw/ngupdate.asp Official Energy Statistics from the U.S. Government
- US Energy Administration: Electrical Energy Costs http://www.eia.doe.gov/fuelelectric.html
- Critique, contributions wanted: Contact Us to suggest text changes and additions and, if you wish, to receive online listing and credit for that contribution.
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