FIREPLACE BASICS. John LeBaron

Transcription

1 FIREPLACE BASICS INTRODUCTION FIREPLACE BASICS A common sense picturebook looking at fireplace and chimney conditions that can adversely affect the safe operation and structural integrity of your fireplace. John LeBaron

2 FIREPLACE BASICS INTRODUCTION INTRODUCTION: My name is John LeBaron, I am currently a senior inspector and co-owner of Chimney Check Professionals, LLC. I have worked in the various construction trades for most of my adult life (after graduating high school in 1983) and part of my elementary and high school years. I began operating as a general contractor in 1989 and primarily built small to large homes, apartment buildings and condominiums. On occasion I would contract the foundation and slab portions of projects. After the earthquake in 94' I put my focus on the removal and reconstruction of fireplace and chimney systems. In approximately 98' I became aware of the property inspection industry and in 99' I became a full time property inspector for a prominent LA based property inspection referral entity. In 2004 (and approximately 4,500 general property inspections later), after I achieved senior status within the company it was determined that an exclusive (non biased) fireplace/chimney inspection company was needed. We formed Chimney Check Professionals, LLC. I have been performing fireplace chimney inspections ever since. I am now a full time fireplace inspector and train other fireplace inspectors as well. I have intimately observed 8,000 fireplaces. This book or "manuel" has one goal in mind. To give correct information regarding fireplace/chimney systems as to operation, safety, repair standards and etc (from the viewpoint of the inspector). Currently, this book is primarily based on my opinions and my education. Different viewpoints and ideas are encouraged so any valid changes, corrections or additions and ideas will be welcome. This is an "open book" or "open forum" for anyone to submit their views, additional data and even corrections to the existing text. My narrations, pictures and opinions are all based on codes, discoveries in the field and operational standards that I have observed. The concept is that I add to this book as new information is obtained and time allows.

3 FIREPLACE BASICS INTRODUCTION The present form of this book is a very rough first draft. As time allows I will be adding applicable code references and other reference materials. In other words, in time this book will become more complete and hopefully easier to use as a field reference manual for general property inspections, real estate agents, chimney inspectors, technicians and even home owners. My hope is that this book will eventually have all the basic information that a field inspector or observer will need to discover the overall condition of a fireplace system. At a minimum, it would have all the technical information that an inspector would need to perform a fairly competent inspection (in addition to his own experience and expertise). I look forward to hearing you input. John LeBaron (818)

4 FIREPLACE BASICS - DIAGRAMS THE FIREPLACE SYSTEM: MASONRY FIREPLACE: First, there is the classic masonry fireplace system: These systems are typically constructed of brick and mortar and after the mid 1920's steel reinforcements (or rebar) were implemented to help hold the structure

5 FIREPLACE BASICS - DIAGRAMS together during seismic activity. The diagram on the right indicates the typical parts of the modern masonry fireplace system. Due to age, moisture and use and often times improper construction there is typically deteriorated or missing grouting between the flue tiles and the smoke chamber surfaces are often times worn. Since 1927 (and potentially earlier) chimney systems have been required to have liners installed or are required to be constructed of 8 inches thick of masonry. One purpose of this liner (or masonry thickness) is to prevent temperatures in the range of 1700 degrees from passing through the chimney structure and to the wood framing around it which is typically in contact with the masonry chimney.

6 FIREPLACE BASICS - DIAGRAMS NON REINFORCED MASONRY FIREPLACE: This diagram is of a typical early 1900's masonry system. The inner walls of the chimney are unlined limiting ability to contain (or fully direct out the top of the flue system) the products of combustion. The throat area is fairly thin and the breast area is not sloped sharply above the firebox (or is partially horizontal in slope). The thin throat limits the flow of combusted fuel upwards and the flat area above the firebox causes resistance of the rising gases. In many cases a smoke shelf is not present which can allow for back drafting. The downward air flow is not redirected back up but instead flows into the

7 FIREPLACE BASICS - DIAGRAMS living space through the firebox opening. In most cases, the linings (if there is a lining) for these chimneys are worn out. There is also a high possibility that the chimney is cracked. The taller the chimney above the roof the more likely it is cracked. If you see a horizontal crack in the stucco (somewhere around the roof line) you potentially have a cracked chimney. These systems often times do not draft correctly and there is generally smoke staining at the lintel area and often times outside the firebox. DRAFTING: simply stated is the pulling of the combusted fuel up and out the top of the chimney system.

8 FIREPLACE BASICS - DIAGRAMS MASONRY FIREPLACE WITH A COMBINATION MASONRY AND PREFABRICATED CHIMNEY COMBINATION: Often times when the chimney system is constructed of partial masonry and partly a prefabricated metal flue system it was damaged in an earthquake. The original masonry would have been removed to the crack or appropriate location and then reconstructed with a metal flue system.

9 FIREPLACE BASICS - DIAGRAMS For a period of time (after the 94 earthquake) contractors could get "certified" by the city and were allowed to perform chimney repairs without the benefit of city inspections. It is the exception when I find a chimney repair that fully meets city and manufacturers standards. In many cases, the metal flues are in contact with or very close to combustible materials. Horizontal firestops will be missing, required bracing of the chimney will not be present or it will be inadequate, too small of metal flue is sometimes used and etc. Very often, the point where the masonry meets the metal flue system is not sealed properly to ensure that no passage of heat or combusted fuel enters into areas not intended for this purpose. In most cases, only the damaged portion of the structure was addressed leaving the remaining system worn and deteriorated, thus leaving potential fire safety issues un-addressed.

10 FIREPLACE BASICS - DIAGRAMS MASONRY FIREPLACE WITH A PPREFABRICATED METAL FLUE SYSTEM: This is what is sometimes known as a Hi-Temp chimney repair. Wood framing for this type of repair has not been allowed since approximately august 18 of 1994 (in most cities). I believe Simi Valley still allows it and other parts of Ventura may still allow it. Glendale, Burbank and other areas may have allowed wood framing until recently. The LA city standard (most surrounding cities have adopted this standard,

11 FIREPLACE BASICS - DIAGRAMS but don't typically call it the LA City Standard) only applies for a "repair". This standard can typically be bypassed if the "repair" is designed by an engineer and the city has approved it. If the metal flue system is an extension then the LA city standards may not apply as well. Wood framing might be used. Shroud covers are typically not a good idea and some metal flue manufacturers specifically indicate they are not to be used. It is specifically important for an air cooled pipe (or one that does not have insulation between the inner and outer flue walls). Shroud covers can limit the air flow around the termination cap/spark arrester which limits drafting and cooling of the metal flue system.

12 FIREPLACE BASICS - DIAGRAMS OFFSET SMOKE CHAMBER: Masonry systems During the rise of the combusted fuel, turns, twists and rough surfaces lead to resistance and in some cases improper drafting (or the entry of combusted fuel into the living space through the firebox opening). Ideally, a smoke chamber should not have flat (horizontally) surfaces and should have a maximum 45 degree slope.

13 FIREPLACE BASICS - DIAGRAMS REQUIRED DISTANCES TO COMBUSTIBLE MATERIALS AROUND THE FIREPLACE OPENING: NOTE: Drywall and stucco paper are combustible materials and should not be inside the firebox or within 6 inches of the firebox opening as indicated in the UBC. In some cases I will see lath paper or drywall placed between the masonry (in contact with) and tile or veneer pieces.

14 FIREPLACE BASICS - DIAGRAMS GROUTING BETWEEN FLUE TILES: If the grouting between the flue tiles was never installed or is deteriorated then it may not prevent (in all cases) heat from passing through the masonry structure and to the wood framing of the house. CHIMNEY HEIGHT REQUIREMENTS: The chimney height requirement typically has to do with fire safety and drafting of the chimney system.

15 FIREPLACE BASICS - DIAGRAMS As I see it, if a chimney looks dwarfed or does not "stand out" it is probably too short. We are used to seeing chimneys extend above roofs and when the roofs are steep the chimney structure will extend high above the roof line. If you take note, you will probably notice that most chimneys will "catch your eye" because of this height requirement. If a one story chimney is 9 feet from a 2 story addition one would have to use "judgment". A minimum, I make the owner/buyer aware of the condition and the potential downfalls.

16 FIREPLACE BASICS - DIAGRAMS CLEARANCE REQUIREMENTS TO CHIMNEYS: It is a very little enforced requirement that there be a 2 inch minimum distance between the wood framing and the masonry chimney. If you look inside attics you will usually see the ceiling framing in contact with or very near the chimney. You will also see the roof rafters close or touching as well. The plywood sheathing will many times be in contact. This requirement has changed over the years from 0 inches to 4 inches and "back again".

17 FIREPLACE BASICS - DIAGRAMS This is one of those requirements where the reality is that most homes violate it and there does not seem to be fires as a result of this one violation. I tend to focus on the inner lining of the chimneys and only talk about the exterior clearance requirements when conditions are excessive. One could say that judgement is needed or as a chimney inspector I would be requiring that the framing around the chimneys of most every house be modified at significant cost. PREFABRICATED FIREPLACE SYSTEMS: In essence, this is a puzzle with a specific installation requirement. Both the city and the manufacturer have their standards. The stricter of the two is

18 FIREPLACE BASICS - DIAGRAMS supposed to be followed. In my experience the most common problem with these systems is user error during installation. NOBODY SEEMS TO WANT TO READ THE MANUAL. COMMON ERRORS: Improper clearances to combustibles (generally, there are labels on the components specifying the requirements) both around the firebox opening, within the chase and around the firebox. This is a requirement that I do not see as "grey" that I sometimes feel is with a masonry chimney. Improper components utilized within the system, such as an improper log grate (in some cases prevents proper drafting), improper spark arrester/ termination cap and the installation a shroud cover (which limits drafting and cooling of the flue system and sometimes the firebox). Partially or fully disconnected flue pipe, either an inner or outer wall. Missing horizontal firestops within the attic space, allowing for debris to fall on top of the firebox and come in contact with the metal flue system. This also violates codes standards. Improper clearances to building materials or combustible materials is one of the most common errors with the metal chimney installation. The outer wall of the flue can get very hot and in time cause ignition of the wood framing, materials or debris around it. Not achieving the correct height for the chimney system. Most manufacturers require at least a 14 foot system, some 15 feet and a few 12 1/ 2 feet (the system is measured from the bottom of the firebox to the top of the metal flue.

19 FIREPLACE BASICS - DIAGRAMS DISCONNECTED FLUE: This picture is worth a second look to emphasize that I find quite a few disconnected or partially disconnected prefabricated flues. From brand new homes to older ones: Do not think that because it is a new or newer home that the fireplace system does not need an inspection. No installation is "immune" to improper installation. A brand new home has no less of a need for a fireplace inspection than it does for a general inspection. In my opinion, this is because general contractors install the prefabricated fireplace systems "in house" which opens the door to improper installation which is more common than not.

20 FIREPLACE BASICS - DIAGRAMS FINISH MATERIALS: Finish materials must not block the opening of the firebox or any vents that assist in the cooling of the system. Combustible finish materials arew also required to be a distance from the firebox opening (this is determined by the manufacturer of each fireplace system. Hearth extensions for prefabricated systems: Generally, the finish tiles can be placed directly on wood surfaces.

21 FIREPLACE BASICS - DIAGRAMS GAS APPLIANCE WITH A MASONRY CHIMNEY: A gas appliance that passes through a masonry structure has similar requirements (such as a liner) as a fireplace system. This type of system is typically not inspected by me but I will often times see a gas appliance that utilizes the fireplace chimney structure to vent its gases through a separate flue system.

22 FIREPLACE BASICS - DIAGRAMS I will always recommend that the appropriate appliance specialist be consulted to ensure that the venting "system" is adequate for the specific gas appliance. GAS APPLIANCE: It seems to be less common for gas appliance systems to be installed improperly but it still happens enough to take a closer look. Many of the vent pipes are installed similarly to water heaters (the 1 inch to combustible clearance requirement is ignored). Often times the pipes are

23 FIREPLACE BASICS - DIAGRAMS disconnected or upside down. More common than not there is inadequate strapping of these pipes. DIRECT VENT: Direct vent systems are peculiar and typically are "closed" systems with a "sealed" glass panel over the firebox opening and a dual wall vent pipe that allows for the exit of the combusted fuel and has a separate passageway from the combustion air (required for proper operation of gas appliance). Common mistakes: The removal of the glass panel will allow the combusted fuel to enter the living space and also allows heat to enter areas not intended for heat. Clearances to combustibles (from the vent pipe) are also commonly incorrect.

24 FIREPLACE BASICS - DIAGRAMS WOOD STOVES/FREESTANDING FIREPLACES: Wood stoves and free standing fireplaces are uncommon and have their own set of standards. I rely on a field manual when I run into these (probably about once every 6 months). I rely on my basic understanding of how a fireplace operates and general fire safety standards for most of my inspection on a free standing or wood stove system. A key flaw to these systems is the upper chimney installation beginning at the ceiling line. Clearances to combustibles are usually inadequate, pipe strapping is typically not present and there is usually debris and/or wood framing in contact with the metal flue in the attic or chase. Often times, these installations appear to be by the "home owner" or handyman type. I consider these systems to be well justified for an inspection since most (in my opinion) were not installed by professionals.

25 FIREPLACE BASICS - DIAGRAMS INSERTS: Inserts are not common and have a wide range of requirements. One of those requirements is that an insert can only be installed in an undamaged system and "working" fireplace system. If a chimney is broken, an insert is not an option. Inserts rarely can be installed in prefabricated fireplace systems. I have heard that this is sometimes allowed but have not seen a prefabricated fireplace system yet that allows for an insert application. If the inner liner of the masonry chimney is damaged or worn, then the insert would have to have its own liner (most systems require a separate flue within the chimney regardless). There are variables as far as the "liener" requirements are concerned. Inserts are rare and I have only inspected a few. I will usually contact the manufacturer (for installation requirements) when I run into one.

26 Photographs PHOTOGRAPHS The following pictures and narratives are taken from my past inspections. The purpose is to show common problems I run into in the field (as an inspector) and to give a basic understanding as to why we "should not" see this in the field. As an inspector I have found that over 90 percent of fireplace/chimney systems are in need of either repairs, reconstruction or corrections due to age, wear, earthquake damage and very often poor installation. A new installation is not "immune" to poor and potentially hazardous workmanship. It is my theory that the reason most of these "problems" do not manifest into actual fires is because most people in the LA area do not use their fireplaces. As an inspector it would be inappropriate to assume that my client is going to have the same operational habits as the current owner. In other words, the fact that there has not been a fire as a result of a sub-standard system does not mean that there will not be one with the new owner or present owner (given enough time and use). A fireplace system is no different than an electrical system, roof or foundation. Just because a roof is not leaking or a cracked foundation has not caused walls to fall in does not mean corrections are not required. A faulty electrical system from the 20's is still faulty regardless of lack of incident. As a home inspector I have seen many homes that were in very poor condition and people were actually living in them. This did not remove the need for significant upgrades to the house. It only meant that individuals had apparently lived in the house without significant incident so far. My job as the home inspector was then to inform the buyer where his "potential trouble spots were" not to tell him/her he had to do anything about it, just recommend that they do. As a fireplace inspector the job is the same. Just because there have been no apparent fires or structural damage caused by a fireplace or chimney does not mean that we ignore faulty or damaged systems.

27 Photographs The findings and recommendations should always follow city, code, fire safety and structural standards. A correct inspection is a "standard inspection" in which recommendation "A" will always follow condition "A".

28 SHROUD COVERS: Shrouds are decorative covers placed at the top of wood or steel framed chimney systems (and sometimes at the tops of masonry chimneys). They are generally not "allowed" by manufacturers of prefabricated metal flue systems since they were not tested with the system by an authorized testing agency or the manufacturer. They can restrict the flow of air through and around the termination of the flue system which can limit drafting and cooling characteristics of chimney systems. Significantly restricted air flow Air flow significantly restricted

29 Restricted air flow Restrictive

30 Restrictive Restrictive

31 POTENTIALLY SERVICEABLE SHROUD COVERS: IMPROPER TERMINATIONS: Likely serviceable These shroud covers are likely not restrictive but may still not be approved by the manufacturer of the fireplace. Moisture can enter and cause rust/damage Only the approved manufacturers termination cap (combination spark arrester and rain cap) assembly is allowed to be used at the top of prefabricated flue systems (either air cooled or class "A"). One of the purposes of a termination cap (or chimney top - other terms are used as well) is to help prevent the intrusion of moisture into the flue system or chimney system. In the case of prefabricated flue systems it also acts as as spark arrester (aiding in fire safety). Presently (as with metal flues), the common spark arrester for masonry fireplaces includes a rain cap.

32 The installation of a termination cap can restrict the flow of combusted fuel up and out the top of the chimney. This can allow for smoking (or the entry of combusted fuel into the living space through the fireplace opening) which is considered a health and safety risk. It is important that a proper termination cap be installed so that it performs its purpose but at the same time does not prevent proper operation of the fireplace system. Metal flue within masonry structure This particular chimney system is constructed of brick "around" a metal flue pipe. There is no city standard that allows this and the manufacturer of the metal flue does not allow this as well. It is also open at the top which allows for rain water to flow down the metal pipe which will eventually destroy the pipe due to rust.

33 Caps either too low or blocking opening Solid materials at the tops of chimneys which partially block the openings constrict the flow of combusted fuel.

34 IMPROPER EXTENSIONS or REPAIRS: Extended by about 3 feet Improper extensions (in masonry) can add significantly to the weight of the structure which can be compounded during seismic activity. The city generally will not allow extensions constructed with masonry. There are always exceptions but typically require engineering. Extended by 2 feet and also broken at roof

35 CHIMNEY CHASE INADEQUATE BRACING: All are easily moved when pushed on. A wood or metal framed chase or chimney structure (which encloses a metal flue system) should be "strong" enough to withstand wind loads as well as the effects of seismic activity. The roof structure should also be adequately re-enforced to support the load of the "chimney" structure.

36 CHASE COVERS: Chase cover dips, improper water runoff A chase is an enclosed passageway for a prefabricated chimney system. Since a chase is typically constructed of exterior walls and an open space between there needs to be a cover at the top to prevent the elements from entering. This cover is typically called a chase cover and is supposed to be removable for service and inspection (among other requirements). Chase covers should be constructed in manner as to keep the "weather" out. If the cover is flat or dips towards the flue opening then there may be standing water. If there are holes or openings then water may pass through. Generally, there should be openings between the cover and the top of the chase to allow for air circulation. This has much to do with the proper cooling of the metal chimney.

37 METAL FLUES: Gas appliance vent cut and "placed" collar Manufactured flues are usually not allowed to be modified. Anything other than attaching the components as designed is typically going to void the manufacturers warranty and is a potential health and safety issue.

38 Outside elbow has a disconnected component Pipes are supposed to be strapped properly to support the weight of the vertical piping and to hold the piping secure. Improper or no strapping can cause damage and disconnected flue sections. Arrow points to only 1/3 of fireplace open This pipe is not attached at the top of the firebox.

39 Lances exposed - partial disconnection A partially disconnected flue can allow (in the extremes) for the heat to pass into areas not intended. IMPROPER HEIGHTS: LANCE: In this case the lance is part of the interlocking component which enables a solid connection between the upper and lower pipe section. Too close to added deck A chimney that does not "stand out" (in most cases) when viewed from the street is potentially too short. As a rule a chimney will "dominate" the look of a roof or exterior view unless it is partially missing or constructed incorrectly. A "short" chimney probably has more wrong than just the height.

40 The left chimney is almost touching the wood framing around the flue (there should be a minimum of 2 inches clearance for this particular flue. The right chimney was broken at the shoulder and improperly "rebuilt" only a few feet above the lowest edge of the roof. In this situation, the chimney should be about 8 feet taller and should not be constructed of masonry.

41 IMPROER CLEARANCES: Wood and mastic touching flues Manufacturers of prefabricated flue systems have required clearances to combustibles (2 inches is the general rule) and building materials (the minimum that I have seen is 1 inch and very rarely have I seen 3 inches) As a chimney inspector I very specifically call out any clearance related issues as this can be a fire safety risk. Roof mastic is a combustible material and so are many decking surfaces (the manufacturer of the deck materials may have to be consulted to determine whether or not it may be in contact with a metal flue system).

42 FIREPLACE BASICS - PHOTOS Drywall and wood too close Drywall is a combustible material by one of the definitions in the code book. The bottom left image shows a 2 by 4 that is almost touching the collar area on top of the firebox. This constricts the flow of air though the inner walls of the flue system and is a significant fire safety issue. Left-gobs of mastic. Right wood-contact Folklore would indicate that it is not necessary to inspect brand new construction. I probably see more clearance issues with brand new construction than older.

43 LINERS: "Dirt" in chimneys can act as a fuel Debris and creosote build-up can ignite and create a chimney fire that can reach temperatures in excess of 1700 degrees. This high heat can melt metal flue systems and crack clay liners and sometimes the masonry structure. It is very important to keep a system cleaned and maintained. Cleaning a system does not bypass the need for a system to meet standards but risks may be lowered. Heat transference (to the wood framing of the structure) can also occur over long term use as the wood framing dries out and its point of ignition lowers.

44 Gas appliance liner used for maonry flue The 4 inch metal liner is not rated for solid fuel and the size of the flue does not allow for a proper drafting of the system. This is a masonry fireplace and a gas appliance vent was used as a liner (within the existing chimney). About 20 percent of the metal flue is visible and is significantly smaller than it should be. View from roof then without cap The liner is one of the barriers that prevents the heat from passing to the wood framing of the house. It also is the intended passageway for the combusted fuel (to ensure it escapes to a "safe" location). If there are gaps, holes, voids or deteriorated areas of the liner system then we have potential breaches that can allow for the gases to pass through the structure and into the living space. Heat can also pass through. A clay liner system is not intended as "form" material to hold the rebar in place. It is a heat barrier and the grouting between the clay tiles is also part of the heat barrier. LINER: A liner is typically a "barrier" of some type that helps to prevent heat transfer. Liners are typically made of clay tiles,

45 mortar coating or metal. This chimney is also broken at the roof I personally have found single wall brick construction (with or without a mortar liner) to be the most prone to allowing ignition to the wood framing around it. During my years removing and rebuilding chimney systems it is the single wall construction chimneys which I found charred or burnt wood just above the firebox area. If a system is pre 1935 there should be an added emphasis for a specialty inspection. Liner and grouting completely worn This system is literally being held together by the exterior stucco.

46 This mortar coating is no longer capable of performing its intended function during extremes.

47 DAMAGED FLUE SYSTEMS: Same chimney This particular chimney has a gas appliance venting through a separate clay tile flue. But both the fireplace and appliance flues are broken and partially missing. This allows for backdraft of the appliance exhaust into the living space. This chimney is not realistically repairable because there is no support for the clay tiles.

48 Flues open to each other at smoke chamber This picture is a view of two flue systems contained within one chimney structure. Each fireplace should have its own independent flue. Single wall brick added to existing City standards requires 8 inches thick of masonry for a chimney (the clay tile is considered 4 inches). It must also be re-enforced masonry. But, extending a masonry chimney with masonry is typically not allowed due to past earthquake issues.

49 IMPROER TRANSITION FROM MASONRY TO METAL: Arrows indicate flat surfaces The shape of a smoke chamber is important for drafting reasons. It should be adequately tall so that the slope of walls do not exceed 45 degrees and there should not be any flat areas. This smoke chamber is too short (since the rebuild) and has no "transition" where it meets the class "A" pipe.

50 SMOKE CHAMBERS: Mortar coatings worn out Smoke chamber liners (most often mortar coatings) have the same requirements as flue systems as the smoke chamber has the same potential for heat during a chimney fire as the flue portion. If the mortar coating is missing, falling off or soft it should be re-lined. Whitish coloring of the mortar surfaces are an indications of "soft" mortar.

51 Worn out and unlined smoke chambers Corbeled and unlined surfaces create resistance of the combusted fuel upwards. This can allowed for smoking into the living space due to poor drafting.

52 FIREPLACE - SMOKE STAINS Smoke stains (in and out), poor drafting A firebox that that has smoke stained walls generally does not draft correctly or has drafted improperly in the past. Older fireplaces have a greater tendency to draft incorrectly due to changing intents: At the turn of the century we were relying on fireplaces to partially heat the home and there was not as much concern on whether or not we were breathing combusted fuel. We have now learned that these fumes are toxic and smoke stains at the lower areas and the very front portions of the firebox walls generally indicates that combusted fuel is entering the living space to some degree and for health and safety reasons some sort of correction is warranted.

53 Prefabs should never "smoke" A smoking condition with a prefabricated fireplace is more obvious and more clear as a non-optimum condition as they are "engineered" and if installed correctly (per manufacturers instructions) they should not smoke. Under extreme conditions (such as weather, atmospheric conditions, hillsides, trees and etc. they can smoke regardless).

54 Poor design of lintel and breast areas On masonry fireplaces the shape of the surfaces above the fireplace can significantly affect the flow of combusted fuel upwards.

55 COMBUSTIBLES TOO CLOSE TO OPENING: L- framing too close. R - paper at facing On masonry fireplaces there are minimum clearances to combustibles at the opening of the fireplace. Prefabricated fireplaces have minimums as well. Top left is a prefabricated fireplace On a prefabricated fireplace, the minimum distance varies and is dictated by the manufacturer. Usually the installation instructions are not available so an absolute minimum would be for there to not be combustible materials in front of or in contact with the metal facing of the firebox.

56 LOGS AND GRATES: Left - too large. Right - wong for prefab Prefabricated fireplaces have specific log grates that are allowed and typically there will be a "tab" within the firebox that two or more legs attach to. Log grates are designed to contain the solid fuel (or gas logs) and if the fuel is too far forward within the firebox then the combusted fuel can have a tendency to drift into the living space instead of being properly drawn through the flue system. "Logs" too large Just because you can't see the combusted fuel entering the living space does not mean it is not.

57 PREFAB BOX "CLOSED OFF": Prefabricated fireplaces should not have finish materials that constrict the opening of the firebox area. This can prevent proper cooling of the firebox area (there are usually vents that allow for air circulation within the firebox structure that cools the system. This prevents the installation of glass doors and may affect the drafting characteristics of the system.