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Fireplace on Church  Hill, Stewart Island, New Zealand (C) Daniel Friedman Fireplace & Hearth: Design Specifications & Safety Inspections
Fireplace construction, inspection & repair

  • FIREPLACES & HEARTHS - CONTENTS: fireplace design, build, & safety inspection recommendations including: Fireplace flue size requirement, Chimney / Fireplace Settlement. Chimney / Fireplace Support Repair. Fireplace Damper Trouble. Fireplace Fire Hazards: Carpeting too close to fireplace opening or hearth, Fireplace Hearth Size
  • POST a QUESTION or READ FAQs about inspecting, diagnosing, & repairing fireplace damage from settlement, cracks, masonry movement
  • REFERENCES
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Fireplaces & hearths, construction, inspection and repair:

This article series provides information about masonry fireplaces, including inspection for damage/hazards (cracks and gaps that appear at masonry fireplaces due to chimney or fireplace settlement or movement), fireplace chimney sizing requirements, draft problems, chimney safety, creosote problems, inserts, and other topics.

Fireplace damage from chimney or fireplace settlement or movement may be a fire or gas hazard in a building Fireplace hearth size specifications; How to add support below a settling fireplace hearth. Fireplace damper inspection, diagnosis, repair or replacement. Photo examples of cracks in on and around masonry fireplaces and a guide to their cause and remedy. Masonry fireplace chimney & flue size requirements & hearth dimension codes.

Our page top photo shows a lovely fireplace in a Church Hill restaurant on Stewart Island, New Zealand.



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Masonry Fireplace Specifications, Safety Hazards, Recommendations

Carpet at fireplace (C) Daniel FriedmanArticle Series Contents

[Click to enlarge any image]

The combustible carpet in front of the fireplace shown here is just a few inches from the fireplace doors and is a fire hazard. Details are in this article.

Fireplace Design Specifications Summary

Table R1001.1
Summary Of Requirements For Masonry Fireplaces And Chimneys [USA]

Fireplace Component / Item

Illustration Key
in
Figure R1001.1.

Requirements Comments
Hearth slab thickness A 4"  
Hearth extension
(each side of opening)
B 8″ fireplace opening < 6 square foot.
12″ fireplace opening ≥ 6 square foot.
FIREPLACE HEARTH DIMENSIONS & SUPPORT
Hearth extension
(front of opening)
C 16″ fireplace opening < 6 square foot.
20″ fireplace opening ≥ 6 square foot.
Hearth slab reinforcing D Reinforced to carry its own weight and all imposed loads. FIREPLACE SAFETY: CRACKS, SETTLEMENT
Thickness of wall of firebox E 10″ solid brick or 8″ where a firebrick lining is used. Joints in
firebrick 1/4″ maximum.
 
Distance from top of opening to throat F 8"  
Smoke chamber wall thickness
Unlined walls
G 6"
8"
 
Chimney
Vertical reinforcing b
H Four No. 4 full-length bars for chimney up to 40″ wide. Add two
No. 4 bars for each additional 40″ or fraction of width or each
additional flue.
b. Not required in Seismic Design Category A, B or C.
Horizontal reinforcing J 1/4″ ties at 18″ and two ties at each bend in vertical steel. CHIMNEY CRACK DETECTION & DIAGNOSIS
Bond beams K Not specified.  
Fireplace lintel L Noncombustible material.  
Chimney walls with flue lining M Solid masonry units or hollow masonry units grouted solid with
at least 4 inch nominal thickness.
UNLINED FLUE INSPECTIONS
Distances between adjacent flues - See Section R1003.13. FLUE SEPARATION REQUIREMENTS
Effective flue area (based on area of fireplace opening) P See Section R1003.15. FIREPLACE FLUE SIZE vs OPENING DIMENSIONS
Clearances:
Combustible material
Mantel and trim
Above roof
R See Sections R1001.11 and R1003.18.
See Section R1001.11, Exception 4.
3′ at roofline and 2′ at 10′.

CHIMNEY CLEARANCE & CONDITION SAFETY

CHIMNEY CLEARANCE to NEIGHBORS

CHIMNEY HEIGHT & CLEARANCE CODE

Anchorage b
Strap
Number
Embedment into chimney
Fasten to
Bolts
S 3/16″ × 1″
Two
12″ hooked around outer bar with 6″ extension.
4 joists
Two 1/2″ diameter.

b. Not required in Seismic Design Category A, B or C.

CHIMNEY COLLAPSE RISKS, REPAIRS

CHIMNEY MOVEMENT CAUSES

Footing
Thickness
Width
T 12″ min.
6″ each side of fireplace wall.

Note that these are minimums. Soil conditions in some areas may require larger footings.

CHIMNEY LEANING, SEPARATION, MOVEMENT

CHIMNEY FOOTING DEFECTIVE / MISSING

Additional Recommendations [not in the ICC code notes - Ed.]:

Chimney Flue Size Requirements

Combustion air requirements

Fireplace damper inspection & operation

   

 

FLUE SIZE SPECIFICATIONS

COMBUSTION AIR DEFECTS

FIREPLACE DAMPERS

       

Notes to the fireplace design table:

Source: 2006 Virginia Residential Code that in turn excerpts from the 2006 ICC, Chapter 10, Chimneys and Fireplaces, Section R1001 Masonry Fireplaces, retrieved 2016/07/13, original source: http://www2.iccsafe.org/states/virginia/
Residential/PDFs/Chapter%2010_Chimneys%20and%20Fireplaces.pdf

For SI: 1 inch = 25.4 mm, 1 foot = 304.8 mm, 1 square foot = 0.0929m2.

This table provides a summary of major requirements for the construction of masonry chimneys and fireplaces. Letter references are to Figure R1001.1, which shows examples of typical construction. This table does not cover all requirements, nor does it cover all aspects of the indicated requirements. For the actual mandatory requirements of the code, see the indicated section of text.

Note a. The letters refer to Figure R1001.1. given just below [Click to enlarge any image]
Note b. Not required in Seismic Design Category A, B or C.

[Click to enlarge any image]

Fireplace & Chimney Design Details - Virginia Code 2006 derived from ICC Chapter 10 Chimneys and Fireplaces, Masonry

Masonry Fireplace Chimney & Flue Size Requirements

This information is now found in a separate article at FIREPLACE FLUE SIZE SPECIFICATIONS

According to the Masonry Institute of America, the required flue size for masonry fireplaces (burning wood) is basically a function of the area of the fireplace opening. Typical standards require a cross-section area of the fireplace flue or chimney/vent to be equal to 1/10 of the area of the fireplace opening itself, for a conventional wood-burning installation and without considering the effects of a glass fire-door.

The FHA requires using a 1/8 ratio instead of 1/10 for chimneys that are less than 15 feet high and the 1/10 ratio for chimneys that are 15 feet or more tall. [9]

Fireplace Hearth Size Requirements: Hearth Dimensions

This topic is now found in a separate article: see FIREPLACE HEARTH DIMENSIONS & SUPPORT

Antique fireplace used for cooking, Brinstone Farm, St. Weonards, U.K. (C) Daniel Friedman

Above, an antique fireplace used for cooking, Brinstone Farm, St. Weonards, U.K. To the left of the fireplace you can see a clay-cover over a huge built-in cauldron that was used to heat water, or perhaps when the farm was at full staff, soup.

Support Below a Fireplace Hearth

Please see FIREPLACE HEARTH DIMENSIONS & SUPPORT

Fireplace Damage and Unsafe Hearths due to Chimney or Fireplace Settlement

Our discussion of unsafe fireplaces & hearths including hearth settlement, cracks in the fireplace box and other unsafe conditions is now found at FIREPLACE SAFETY: CARPETS, CRACKS, SETTLEMENT

More unsafe hearths and inadequate clearance from fireplaces or wood or coal stoves are shown at FIRE CLEARANCES, WOOD & COAL STOVE FLUES.

Watch out: while this particular article series discusses fireplace dangers & fire risks related to cracks or settlement in the fireplace chimney, the most common fire hazard associated with fireplaces is a chimney fire caused by the ignition of accumulated creosote in the fireplace chimney flue.

See CHIMNEY FIRE ACTION / PREVENTION

and

See CHIMNEY CLEANING PROCEDURE - home

Fireplace Damper Trouble Inspection, Diagnosis, Repair

Please see details at this article: FIREPLACE DAMPER DEFECTS, REPAIRS

A fireplace damper is a metal door installed in the fireplace chimney throat. To avoid wasting building heat by sending it up the chimney when a fireplace is not in use, the fireplace damper door is closed when the fireplace is not in use.

Fireplace & Woodstove Articles

...


Continue reading at FIREPLACE DAMPER DEFECTS, REPAIRS or select a topic from closely-related articles below, or see our complete INDEX to RELATED ARTICLES below.

Or see AUTOMATIC FIRE SMOKE DAMPERS

Or see FIREPLACE INSERTS

Suggested citation for this web page

FIREPLACES & HEARTHS at InspectApedia.com - online encyclopedia of building & environmental inspection, testing, diagnosis, repair, & problem prevention advice.

INDEX to RELATED ARTICLES: ARTICLE INDEX to CHIMNEYS & FLUES

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