780 CMR 60.00 CHIMNEYS, FIREPLACES AND SOLID FUEL-BURNING APPLIANCES 780 CMR 6001 MASONRY CHIMNEYS least two feet (610 mm) higher than any portion of a 6001.1 General. Masonry chimneys shall be building within 10 feet (3048 mm), but shall not be constructed, anchored, supported and reinforced as less than three feet (914 mm) above the highest point required in 780 CMR 60.00 and the applicable where the chimney passes through the roof. provisions of 780 CMR 53.00, 54.00 and 56.00. 6001.6.1 Spark Arrestors. Where a spark Chimneys shall be structurally sound, durable, arrestor is installed on a masonry chimney, the smoke tight and capable of conveying flue gases to spark arrestor shall meet all of the following the exterior safely. requirements: 6001.1.1 Support. Masonry chimneys shall be 1. The net free area of the arrestor shall not be supported on foundations of solid masonry or less than four times the net free area of the concrete at least 12 inches (305 mm) thick and at outlet of the chimney flue it serves. least six inches (152 mm) beyond each side of the 2. The arrestor screen shall have heat and exterior dimensions of the chimney. Footings corrosion resistance equivalent to 19-gage shall be founded on natural, undisturbed earth galvanized steel or 24-gage stainless steel. below the frostline. In areas not subject to 3. Openings shall not permit the passage of freezing, footings shall be located a minimum of spheres having a diameter greater than ½ inch 12 inches (305 mm) below finished grade. (12.7 mm) nor two block the passage of spheres having a diameter less than d inch (9.5 6001.2 Corbeling. Masonry chimneys shall not be mm). corbeled more than one-half of the chimney’s wall 4. The spark arrestor shall be accessible for thickness from a wall or foundation, nor shall a cleaning and the screen or chimney cap shall be chimney be corbeled from a wall or foundation that removable to allow for cleaning of the chimney is less than 12 inches (305 mm) in thickness unless flue. it projects equally on each side of the wall, except that on the second story of a two-story dwelling, 6001.7 Wall Thickness. Masonry chimney walls corbeling of chimneys on the exterior of the shall be constructed of solid masonry units or hollow enclosing walls may equal the wall thickness. The masonry units grouted solid with not less than a projection of a single course shall not exceed four-inch (602 mm) nominal thickness. one-half the unit height or one-third of the unit bed 6001.8 Flue Lining (Material). Masonry chimneys depth, whichever is less. shall be lined. The lining material shall be 6001.3 Changes in Dimension. The chimney wall appropriate for the type of appliance connected, or chimney flue lining shall not change in size or according to the terms of the appliance listing and shape within six inches (152 mm) above or below manufacturer’s instructions. where the chimney passes through floor components, 6001.8.1 Residential-type Appliances ceiling components or roof components. (General). Flue lining systems shall comply with one of the following: 6001.4 Offsets. Where a masonry chimney is constructed with a fireclay flue liner surrounded by 1. Clay flue lining complying with the one wythe of masonry, the maximum offset shall be requirements of ASTM C 315 or equivalent. such that the centerline of the flue above the offset 2. Listed chimney lining systems complying does not extend beyond the center of the chimney with UL 1777. wall below the offset. Where the chimney offset is 3. Factory-built chimneys or chimney units supported by masonry below the offset in an listed for installation within masonry chimneys. approved manner, the maximum offset limitations 4. Other approved materials that will resist shall not apply. Each individual corbeled masonry corrosion, erosion, softening, or cracking from course of the offset shall not exceed the projection flue gases and condensate at temperatures up to limitations specified in 780 CMR 6001.2. 1,800°F (982°C). 6001.8.2 Flue Linings for Specific Appliances. 6001.5 Additional Load. Chimneys shall not Flue linings other than these covered in 780 CMR support loads other than their own weight unless 6001.8.1, intended for use with specific types of they are designed and constructed to support the appliances, shall comply with 780 CMR 6001.8.3 additional load. Masonry chimneys shall be through 6001.8.6. permitted to be constructed as part of the masonry walls or reinforced concrete walls of the building. 6001.8.3 Gas Appliances. Flue lining systems for gas appliances shall be in accordance with 248 6001.6 Termination. Chimneys shall extend at CMR. 12/28/07 (Effective 1/1/08) 780 CMR - Seventh Edition 761 780 CMR: STATE BOARD OF BUILDING REGULATIONS AND STANDARDS THE MASSACHUSETTS STATE BUILDING CODE 6001.8.4 Pellet Fuel-burning Appliances. Flue Exception: When venting only one appliance, two lining and vent systems for use in masonry flues may adjoin each other in the same chimney chimneys with pellet fuel-burning appliances shall with only the flue lining separation between them. be limited to the following: The joints of the adjacent flue linings shall be 1. Flue lining systems complying with staggered at least four inches (102 mm). 780 CMR 6001.8.1. 6001.11 Flue Area (Appliance). Chimney flues 2. Pellet vents listed for installation within shall not be smaller in area than that of the area of masonry chimneys. (See 780 CMR 6001.8.6 the connector from the appliance [see 780 CMR for marking.) Tables 6001.11(1) and 6001.11(2)]. The sizing of a 6001.8.5 Oil-fired Appliances Approved for chimney flue to which multiple appliance venting Use with Type L Vent. See 527 CMR 4. systems are connected shall be in accordance with 6001.8.6 Notice of Usage. When a flue is relined 780 CMR 6805.3. with a material not complying with 780 CMR 6001.8.1, the chimney shall be plainly and 780 CMR TABLE 6001 .11(1) permanently identified by a label attached to a NET CROSS–SECTIONAL AREA OF wall, ceiling or other conspicuous location ROUND FLUE SIZESa adjacent to where the connector enters the FLUE SIZE, INSIDE CROSS–SECTIONAL DIAMETER (inches) AREA (square inches) chimney. The label shall include the following 628 message or equivalent language: 738 THIS CHIMNEY FLUE IS FOR USE ONLY 850 WITH [TYPE OR CATEGORY OF 10 78 APPLIANCE] APPLIANCES THAT BURN 10¾ 90 [TYPE OF FUEL]. DO NOT CONNECT 12 113 OTHER TYPES OF APPLIANCES. 15 176 6001.9 Flue Lining (Installation). Flue liners shall 18 254 be installed in accordance with ASTM C 1283 and For SI: 1 inch = 25.4 mm, 1 square inch = 645.16 mm2. extend from a point not less than eight inches (203 a. Flue sizes are based on ASTM C 315. mm) below the lowest inlet or, in the case of fireplaces, from the top of the smoke chamber to a 780 CMR TABLE 6001.11(2) point above the enclosing walls. The lining shall be NET CROSS–SECTIONAL AREA OF carried up vertically, with a maximum slope no SQUARE AND RECTANGULAR FLUE SIZESa greater than 30 degrees from the vertical. FLUE SIZE, OUTSIDE CROSS–SECTIONAL DIMENSIONS (inches) AREA (square inches) Fireclay flue liners shall be laid in medium duty 4½ x 13 34 refractory mortar conforming to ASTM C 199 with 7½ x 7½ 37 tight mortar joints left smooth on the inside and installed to maintain an air space or insulation not to 8½ x 8½ 47 exceed the thickness of the flue liner separating the 7½ x 11½ 58 flue liners from the interior face of the chimney 8½ x 13 74 masonry walls. Flue lining shall be supported on all 7½ x 15½ 82 sides. Only enough mortar shall be placed to make 11½ x 11½ 91 the joint and hold the liners in position. 8½ x 17½ 101 13 x 13 122 6001.9.1 Listed Materials. Listed materials used 11½ x 15½ 124 as flue linings shall be installed in accordance with the terms of their listings and manufacturer’s 13 x 17½ 165 instructions. 15½ x 15½ 168 15½ x 19½ 214 6001.9.2 Space around Lining. The space 17½ x 17½ 226 surrounding a chimney lining system or vent installed within a masonry chimney shall not be 19½ x 19½ 269 used to vent any other appliance. 20 x 20 286 For SI: 1 inch = 25.4 mm, 1 square inch = 645.16 mm2. Exception: This shall not prevent the a. Flue sizes are based on ASTM C 315. installation of a separate flue lining in accordance with the manufacturer’s installation 6001.12 Flue Area (Masonry Fireplace). Flue instructions. sizing for chimneys serving fireplaces shall be in accordance with 780 CMR 6001.12.1 or 780 CMR 6001.10 Multiple Flues. When two or more flues 6001.12.2. are located in the same chimney, masonry wythes shall be built between adjacent flue linings. The 6001.12.1 Option 1. Round chimney flues shall have a minimum net cross-sectional area of at masonry wythes shall be at least four inches (602 1 mm) thick and bonded into the walls of the chimney. least /12 of the fireplace opening. Square chimney 762 780 CMR - Seventh Edition 3/23/07 (Effective 4/1/07) 780 CMR: STATE BOARD OF BUILDING REGULATIONS AND STANDARDS CHIMNEYS, FIREPLACES AND SOLID FUEL-BURNING APPLIANCES flues shall have a minimum net cross-sectional area 6001.13 Inlet.