Fireplace insert into chimney (C) Carson Dunlop Associates Fireplace Inserts & Zero-Clearance Fireplaces

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Fireplace inserts:

This article describes the antique and modern fireplace inserts used for wood, coal, or pellet fuel heating.

We discuss fireplace inserts and zero-clearance fireplaces, both antique and modern, and their hazards and inspection limitations.

The page top sketch, provided courtesy of Toronto home inspection firm Carson Dunlop Associates illustrates limitations on the visual inspection of fireplace inserts. It does not show proper fireplace insert installation details.

Green links show where you are. © Copyright 2017, All Rights Reserved.

Antique Fireplace Inserts - Coal-Burning

Below we provide photographs of the exploration of the condition of a cast-iron "fireplace" or fireplace grate that was originally intended for burning large chunks of coal, probably soft coal. This installation was found in a home built in Poughkeepsie NY ca 1900 and restored by the author.

Antique coal burning fireplace Poughkeepsie (C) Daniel Friedman Antique coal burning fireplace Poughkeepsie (C) Daniel Friedman

Watch out: Because a fireplace insert blocks direct access to the chimney flue from inside a building, the condition of an inaccessible flue is often unknown, and possibly dangerous fire or carbon monoxide hazards could be present. Expert inspection and cleaning are appropriate as at least an annual safety check. Our page top sketch of a typical fireplace insert is provided courtesy of Carson Dunlop & Associates.

Working carefully so as not to damage the ceramic tile fireplace facade and hearth, we removed and disassembled this antique coal burning fireplace insert (burning wood in our photo) to inspect the condition and construction of the chimney flue (above right). The flue was un-damaged, needed cleaning, and was also a bit small for any expanded fuel use in this installation.

Antique coal burning fireplace Poughkeepsie (C) Daniel Friedman Antique coal burning fireplace Poughkeepsie (C) Daniel Friedman

Our fireplace photos above show the back and top of this coal burning insert (above left) and the grate assembly (above right).

At below left we show the solid (8" or more) masonry firebox and the opening into a basement ash pit below this fireplace. Our reproduction of an antique fireplace grate insert (below right) was a Dixon's Low-Down Grate. Low fireplace grates were intended for use over an ash pit opening. For upper floor rooms where no ash pit connection was possible, Dixon sold an Elevated Fire Grate.

The installation of low cast iron fire grates over an ash pit was made as shown in this sketch. Dixon's design intended to draw combustion air for the fire from the basement (cellar) or from outside, not from the room being heated - a design considered proper practice in modern homes and required by code in some areas.

Here is another beautiful antique fireplace opening cover/grate observed in Minneapolis and contributed by Roger Hankey.

Watch out: some older homes used a shared flue among fireplaces and heating appliances on different floors - a practice that is considered unsafe and is prohibited today.

Antique coal burning fireplace Poughkeepsie (C) Daniel Friedman Antique coal burning fireplace Poughkeepsie (C) Daniel Friedman

Modern Fireplace Inserts for Burning Wood, Coal, Pellet Fuel

Fireplace insert (C) Daniel Friedman

A modern fireplace insert for burning wood is shown at left. You can see why inspecting the chimney from inside is impossible without removing the appliance.

This installation is particularly interesting. If you click to enlarge the photo you can see light colored bricks at the right of the fireplace insert: the installer appears to have bricked the original fireplace opening to better fit the new insert.

Watch out: adding a fireplace insert that moves the fire doors closer to the edge of the hearth reduces fire clearance (for heat or if the doors are open, sparks and coals) between the appliance opening and nearby combustibles or flooring.

The owners have placed a "fireproof rug" in front of this unit - that semi-circular carpet observed on the floor. Is this adequate? Be sure to consult your local fire inspector when installing or converting a fireplace or fuel burning appliance.


Unsafe Fireplace Inserts

Woodstove inserted (C) Daniel Friedman

By "fireplace insert" we refer to a wood or coal-burning stove designed to be inserted into an existing masonry fireplace opening.

The wood-stove installed in the fireplace at left may work in such a location, but it was not designed as an "insert" - and does not fit the opening of this odd fireplace. In fact not much would fit in this angled firebox.

Placing the feet of the woodstove past the hearth and onto a rug, as well as less than 3' from combustibles, are further fire hazards - this is an unsafe installation.

Zero-clearance Fireplaces

Details about this topic are now at FIREPLACE INSPECTION PRE-FAB - separate article. Excerpts are below

Zero clearance gas fireplace (C) Daniel Friedman

Do not confuse a fireplace insert woodstove or coalstove with a "zero-clearance" fireplace such as the unit shown here.

Zero-clearance fireplaces are typically steel constructed fireplaces to burn wood or perhaps other fuels such as LP or natural gas in modern homes, usually connected to a metal chimney.

Our photo (left) shows a zero-clearance gas fireplace. Other zero clearance fireplaces burn wood or perhaps other fuels.

The clearance to combustibles is not "zero" but one or more inches, depending on the materials, construction, and manufacturers' instructions.

Watch out: we have found a few zero-clearance fireplaces improperly installed too close to combustibles.

The installer did not understand the purpose of steel clearance-assuring projections welded to the zero-clearance fireplace, and s/he had hammered them flat to "shoe-horn" the zero clearance fireplace into a too-small wood-framed rough opening.

The result was a serious building fire hazard and a building code violation as well.

Zero clearance metal fireplace (C) Daniel FriedmanOur photo of a zero-clearance fireplace from inside the framed opening (left) shows the clearance guards intact next to our ruler.

But inspection showed chimney leaks onto this unit - evidenced by the rust and white stains that can ultimately damage the flue (at upper right) and the fireplace unit, making it unsafe.

Inspecting the Chimney where a Fireplace Insert for Wood or Coal is Installed

In fact it is just about impossible to see the condition of these components and their connections unless the insert is removed or inspected from above using a chimney inspection camera system.

If a woodstove/free-standing fireplace like this were to be used it would probably require at least three feet of clearance from combustibles.

Local codes and fire regulations need to be consulted, and in most jurisdictions, a building permit and safety inspection are required for the installation of a woodstove or similar device.

Abandoning or Removing a Fireplace Insert?

Often when a fireplace insert has been installed, the original fireplace damper has been modified (cut to pass the flue vent connector) or simply removed entirely. If you are discontinuing a fireplace insert, you may need to repair or replace the fireplace damper, or perhaps install a chimney-top damper instead.

Factory-Built or Pre-Fab Fireplace Inspection Checklist

Common Factory-Built Fireplace Defects, Problems, Unsafe Conditions

© Copyright 2017, All Rights Reserved. Author Daniel Friedman.

Item # Fireplace, Hearth, or Chimney Defect, Concern, Hazard Comment / More Detail

Building ID & Location: __________________________________________

Date & Time: _________________________________________________

Inspector: ____________________________________________________

1 Chimney & Fireplace Installation: all parts of a factory-built fireplace or chimney must be installed according to instructions provided by the manufacturer and no parts can be damaged to an extent that would impair the function of that part. FIREPLACE INSERTS

2 Chimney & Fireplace Labels: all parts of a factory-built fireplace or chimney system (except in some jursidictions locally-made covers) must bear labels identifying the parts as listed for use with the fireplace model installed in the building. Examples of labeling issues and even counterfeit labels are at CHIMNEY SHROUD, Decorative CHIMNEY INSPECTION CHECKLIST
3 Fireplace air circulators: any louvers, slots or other openings intended to allow air to circulate to and around the fire-box must be clear of obstructions and should not be damaged or have leaks into or out of other building areas or components.  

Factory-built fireplace spacers or supports must be in place and not bent, crushed, or damaged. There should be no combustibles that intrude into the fireplace area past the fire clearance distances indicated by the spacers or by the manufacturer's installation instructions.

5 Floor fire protection: if the fireplace has been installed over a combustible floor a non-combustible safety strip (or other manufacturer specified fire safety and heat protection system) must have been placed underneath the unit and on the floor beneath the hearth extension and the fireplace  
6 Fireplace hearth extension fire protection: the hearth extension must be made of non-combustible materials and of the thickness, depth, and width specified by local building codes & in compliance with the fireplace manufacturer's specifications, OR the hearth extension must be a listed accessory intended for use with the model fireplace installed.  
7 Building insulation installed near the fireplace must be non-combustible and un-faced (e.g. un-faced fiberglass rather than kraft-faced or foil-faced). Where cellulose building insulation is installed it must be shielded and protected from heat that risks combustion, as specified by instructions of the insulation manufacturer and in compliance with local building codes.  
8 Fireplace mounting: the fireplace must be supported and secured or fastened tot he structure or blocked so as to prevent shifting or movement or settlement from its installed position, as specified by the manufacturer.  
9 Mantel, hearth face, other fireplace trim: trim materials at or near the face of the fireplace must comply with both fireplace manufacturer's instructions and local building codes with regard to choice of materials, fire clearance spacing, and fastening methods so as to avoid placing combustible materials too close to a heat source; trim, doors, etc. must be installed without air leaks or gaps as per manufacturer's instructions.  
10 Fireplace modifications: the factory-built fireplace cannot be modified except as permitted by the manufacturer. This includes respecting spacers, trim, mounting locations, and accessories or fire doors.  
11 Fireplace inserts into existing fireplaces or into framed openings may not be installed unless the insert is listed and building-code approved and of course installed according to the manufacturer's instructions. This includes add-on home-heating systems or hydronic systems tying into building heating equipment.  
12 Fireplace chimney & Chimney connections: the chimney should be inspected for proper construction, safe operating condition, etc. as appropriate for the type of chimney materials and construction (masonry, factory-built, etc).










The fireplace owners manual and operating instructions should be provided and should be placed where readily accessible to building occupants. The fireplace identifying tags such as serial number and model number and UL listing or other listing certifications and labels provided by the manufacturer should be intact and left in place as originally installed by the manufacturer.

Additional fireplace safety inspection details are provided at

Inspection checklist warning: No checklist is ever a complete guide to building inspection or diagnosis since no checklist can contain every possible hazard or every clue that suggests a problem. Therefore do not rely on this or any checklist to assure that your inspection of a chimney is complete. Instead, use this list to suggest additional topics that you otherwise may have omitted from your inspection. The more detailed chimney inspection and repair articles at the links at Related Links and the citations below below suggest further, more-detailed chimney inspection points and procedures.

Adapted from chimney inspection safety sources including these documents cited at REFERENCES

  • [3] Wood Heating Alliance, "Building Inspector's Checklist for Factory Built Fireplaces" [PDF]
  • [4] Baird, David J., C.B.O., "Factory-built Chimney Chase Fires: A case for More Detailed Inspection", Building Standards, March-April 1991, pp. 14-17.
  • [5] Purdie, Roger K., "Chimney Fire Safety Bulletin", Vista Fire Protection District, 2001, report of house fire related to the home's metal chimney. Contains advice for chimney * fire safety & sketches of approved and not-code-approved metal chimney tops, caps & crowns. [PDF]
  • [12] Fire Inspector Guidebook, [BOOK] 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.
  • [15] "Top Ten Chimney (and related) Problems Encountered by One Chimney Sweep," Hudson Valley ASHI education seminar, 3 January 2000, contributed by Bob Hansen, ASHI
  • [16] Chimney Inspection Checklist, Carson Dunlop, Associates, Toronto, Ontario
  • [18] "Chimneys and Vents," Mark J. Reinmiller, P.E., ASHI Technical Journal, Vol. 1 No. 2 July 1991 p. 34-38.
  • [19] "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: Copies of earlier editions of the ASHI Technical Journal are available from ASHI, the American Society of Home Inspectors.
  • [20] "Chimney Inspection Procedures & Codes," Donald V. Cohen, draft, was to be published in the first volume of the 1994 ASHI Technical Journal by D. Friedman
  • [25] Chimney Inspection Checklist, Carson Dunlop, Associates, Toronto, Ontario
  • [26] Chimney & Stack Inspection Guidelines, American Society of Civil Engineers, 2003

Reader comment: fireplace flue insertion distance

12/27/2014 Anonymous said:
I thought fireplace insert flues at a minimum must extend to the first tile in the chimney.
The diagram shown here [at the top of this page] does not reflect this.



Quite so. If you are referring to the page top sketch, that drawing does not claim to describe a proper stove insert installation; rather it illustrates areas that are not accessible for visual inspection during a home inspection. Thanks for pointing out that the sketch might confuse someone.

A fireplace insert vertical flue vent connector should indeed pass into the first vertical flue tile, subject to further installation specifications provided by the individual fireplace insert manufacturer. Any flue vent connector that connects horizontaly into a masonry chimney flue needs to be flush with the masonry flue interior. Extending an inch past that point is probably ok but extending too far into the flue horizontally is improper and is likely to block draft.



Continue reading at FIRE CLEARANCES, WOOD & COAL STOVE FLUES or select a topic from closely-related articles below, or see our complete INDEX to RELATED ARTICLES below.

Or see WOOD STOVE INSTALL CONVERT - changing out a zero clearance fireplace for a wood stove


Or see these

Fireplace & Woodstove Articles

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FIREPLACE INSERTS at - online encyclopedia of building & environmental inspection, testing, diagnosis, repair, & problem prevention advice.


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