801.1 Scope. This chapter governs the installation, maintenance, repair and approval of factory-manufactured chimneys, chimney linings, vents and connections. This chapter regulates the use of masonry chimneys. Gas appliances must be ventilated in accordance with the International Fuel and Gas Code. The photo above shows a metal chimney that is too short and less than two feet above the ridge. This chimney spacing specification ensures that steeply pitched roofs are clear. Ideally, you want the chimney to be the highlight of the house – if the top of a house is too high, it can cause it to compete with the chimney for air pressure and reduce efficiency. 801.12 Entrance to the foyer. Connectors must be connected to a chimney located at a point at least 305 mm (12 inches) above the lowest part of the inside of the chimney extractor. The indoor area where smoke and gases circulate is called the chimney and is often the main focal point for chimney sweeps for cleaning. Although this chimney is not found in older chimneys, it was necessary in all homes after the 1950s because it protects the chimney itself from corrosive elements from smoke and gas. Let`s make the same example, but we bring the penetration of the roof closer to the ridge of the roof. Our roof slope is 7/12 and the roof penetration is 4 feet from the ridge.
We take the climb of the roof slope of 7″ (inches of climb per foot) and multiply it by 4 (feet of horizontal stroke to the high point), which is equivalent to 28″ (inches rise to the highest point within 10 feet of the chimney breakthrough). Now we only need 2 feet higher (or 24 inches), so we`ll add 24″ to 28″ to match a total height of 52. In this example, the chimney must protrude 52″ above the roof, measured from the “uphill” side of the chimney. 805.2 Solid fuel appliances. Factory-manufactured stacks installed in solid fuel units must meet UL 103 HT requirements and be labelled “Type HT” and “Residential-type chimneys and building heaters”. A brick wall 3.5 inches thick must be framed within the combustible wall. A 0.625-inch-thick refractory clay liner (ASTM C 315 or equivalent) must be securely cemented in the centre of the brick wall, maintaining a distance of 12 inches from combustible materials. The clay cladding should extend from the outer surface of the bricks to the inner surface of the chimney cladding. Thanks to G. Howard for clarifying the text and thanks to Mark Wolff for pointing out an earlier error in our chimney height illustration – now displayed correctly. [Click on any image to see a larger and detailed version] Chimney roof passage: From the ground you can guess and from the roof access you can measure if a chimney is simply too short for fire safety and compliance.
If there are two or more chimneys in the same chimney, the masonry must be erected between the adjacent cladding. The masonry must be at least 4 inches (102 mm) thick and connected to the walls of the chimney. Exception: If only one appliance is ventilated, two chimneys in the same chimney may be connected to each other, with only the chimney separated from each other. The seals of adjacent exhaust coatings shall be offset by at least 102 mm (4 inches). 805.5 Medium heat appliances. Factory-manufactured stacks for medium-heat equipment that produce flue gases above 538°C (1,000ºF) must comply with UL 959. 801.18 Existing chimneys and vents. If an appliance is permanently disconnected from an existing stack or vent, or if an appliance is connected to an existing stack or vent during a new installation, the stack or vent must comply with sections 801.18.1 to 801.18.4. Note that the “chimney height” is at the top of the chimney opening, not at the top of the chimney cap. I build a chimney on the barn lordship and have questions about how to walk if I am more than ten meters from the ridge. We have a fireplace that has a wood vent and a separate gas fireplace in a single masonry structure. The light cover is farther from the top and meets height requirements (27″).
The gas vent is closer to the top and is only 20″. In this combined chimney, this meets the height requirements. In my opinion, a height difference of 4-6″ is a good chimney design, but this detail is not specified in the model`s chimney codes. 801.18.2 Chimney corridors. The passage of flue gases must be free of obstructions and combustible deposits and must be cleaned if it has already been used to evacuate a solid or liquid fuel appliance or a stack. The exhaust lining, the inner wall of the chimney or the inner ventilation wall must be continuous and free from cracks, holes, perforations or other damage or damage that would allow the release of combustion products, including gases, moisture and creosote. If an oil-fired appliance is connected to an existing masonry brick, the chimney must be repaired or covered in accordance with NFPA 31. Jason, you are absolutely right – the sketch of the side head in the attic also bothered me for a long time, which led to other photos and sketches on this page that correctly showed the required distances. If you have 2 chimneys going through the roof together, how high should the height be between the two or would it be better if you were near the same height just so that smoke could not enter the other chimney? 801.14 Extractor Connections. Connections of the appliance to a chimney or vent with an exhaust must be located on the side of the exhaust inlet. Fittings and piping on the pressure side of the extractor should be listed for overpressure applications in accordance with the manufacturer`s installation instructions for the extractor. In my sketch, the black two-foot-headed arrow shows that the top of the chimney must be two feet above the point of the chimney that would be touched by a ten-foot-long line drawn to the next point of contact with the structure – in this case, the roof surface.
Bruce: Ok, technically, your chimney is one foot short; Maybe I`m not as worried as usual given the very steep roof and the fact that it`s metal, but it`s possible that the chimney doesn`t comply with fire and code for a second reason: I commented on our drawing to show the questionable area in orange when a pitched roof instead of a horizontal ridge top is less than 10 feet or less from a chimney.