Learner Guide 5: Chimneys - Open and Room Sealed Chimney Terminal Locations

Vocabulary flashcards covering the installation rules, minimum clearance dimensions, and regulatory standards for natural draught and fan-assisted chimney terminations (open flued and room-sealed) as detailed in Learner Guide 5.

Flue Outlet Termination Height Measurement Datum

The official measurement reference point for the height of an open chimney termination, which is measured up to the top of the flue outlet (the top of the flue pipe) and not to the top of the terminal itself.

Terminal Locations for Open & Room Sealed Appliances

A standardized alphanumeric positioning layout (dimensions A through P) used to determine minimum separation distances based on the appliance's net heat input ($\text{kW}$) and draught type, ensuring combustion products do not re-enter buildings through openings.

Terminal Guard (Room Sealed Appliances)

A protective cage required to be installed around any room-sealed terminal located within $2\,\text{m}$ of finished ground level to prevent mechanical interference, maintaining a clearance of at least $50\,\text{mm}$ between the guard and all surfaces of the terminal.

Eaves Ventilator Clearances (Post-1983 / Post-1985 Dwellings)

Mandatory clearance distances required between room-sealed terminals and fresh air intake ventilators installed in the eaves of properties constructed after 1985 in England & Wales and after 1983 in Scotland.

Heat Shield Requirements for Natural Draught Terminals

A protective fitting at least $1\,\text{m}$ long with a $5\,\text{mm}$ air gap that must be installed when a natural draught appliance terminates within $1\,\text{m}$ of a plastic gutter or within $500\,\text{mm}$ of painted eaves (under BS 5440 Part 1:2008, fan flued terminals no longer require eaves or gutter protection unless specified by the manufacturer).

Multiple Open Chimney Terminations (Close Proximity Rule)

Regulations governing chimney outlets on shared structures: outlets in close proximity must maintain a minimum spacing of $50\,\text{mm}$, and where $3$ or more terminals are less than $300\,\text{mm}$ apart, they must terminate at the same height.

Staggered Chimney Termination

An arrangement where chimney pots or prefabricated metal terminals are spaced more than $300\,\text{mm}$ apart, permitting them to terminate at different (staggered) heights.

Flat Roof (TOP's Table 5 Definition)

Any roof structure having a slope defined as being within $20^\circ$ of the horizontal plane.

Pitched Roof Clearance (Not on Ridge)

A flue location standard requiring that no part of the chimney outlet shall be less than $1.5\,\text{m}$ measured horizontally to the roof surface, or less than $600\,\text{mm}$ vertically above the ridge.

Ridge Tile Terminal Siting

Terminals positioned on a roof ridge must terminate at or above ridge level, be sited at least $1500\,\text{mm}$ from any adjacent higher structure (such as a gable end wall), and maintain a separation of not less than $300\,\text{mm}$ from other four-sided open ridge terminals.

Roof Structure Clearance (Dimension B)

A clearance rule specifying that if the horizontal distance $A$ from an open chimney terminal to a vertical structure on a pitched roof is less than $1500\,\text{mm}$, the terminal outlet height $B$ must be not less than $600\,\text{mm}$ above the top of that structure.

Pitched Roof Window and Opening Clearance Zone

A restricted area around openings or windows on pitched roofs (irrespective of pitch) where chimneys may not penetrate: extending $A = 600\,\text{mm}$ to the sides and top, and $B = 2000\,\text{mm}$ directly below the opening.

Ten Heights ($10h$) Parapet Rule

A flat roof provision allowing the terminal outlet height to be reduced to only $250\,\text{mm}$ above the roof when the outlet is positioned at a horizontal distance greater than $10$ times the height ($h$) of an adjacent parapet or structure (otherwise $600\,\text{mm}$ is required).

Flat Roof Envelope Method

A method used when multiple structures are on a flat roof and the chimney outlet is within $10h_1$ and $10h_2$ horizontally; the terminal must terminate not less than $600\,\text{mm}$ above an imaginary plane drawn across the roof structures.

Prohibited Zone (Flat Roof Extension / Adjacent Buildings)

A restricted clearance envelope extending horizontally up to $10{,}000\,\text{mm}$ ($10\,\text{m}$) from an adjacent wall, within which a chimney terminal must maintain at least $600\,\text{mm}$ clearance above an inclined line starting $2300\,\text{mm}$ ($2.3\,\text{m}$) above the roof level.

Sloping Hill or Embankment Height Adjustment

A mandatory requirement to increase open chimney terminal heights by $500\,\text{mm}$ when an embankment or sloping hill is within $4$ times the height of the building and has an elevation between $\frac{1}{2}$ and $1$ times the building's height.

Severe Circumstances Termination Specification

Special operating criteria for extreme conditions (such as external chimneys, steep pitch, high efficiency appliances, complex roof geometry, or nearby hills), requiring terminal heights of at least $2\,\text{m}$ and the installation of an extractive terminal.

Boundary (Gas Appliance Siting Definition)

The legal boundary of the land or buildings belonging to and under the control of the property owner, which can be considered to extend to the centre line of adjacent public waterways or routes (such as streets, paths, railways, or canals).

Boundary and Adjacent Terminal Dimensions (X, Y, and Z)

Clearance rules for fanned draught room-sealed terminals near boundaries: Dimension X is $300\,\text{mm}$ parallel to a boundary; Dimension Y is $600\,\text{mm}$ discharging at an angle to a boundary; Dimension Z is $2000\,\text{mm}$ ($2\,\text{m}$) directly opposite an opening in an adjacent building.

Dimension J

The minimum clearance measured from the end face of a terminal to an opposing surface, facing wall, or facing property boundary, specified as $600\,\text{mm}$ for both room-sealed natural draught and fanned draught appliances.

Dimension K

The minimum clearance between two opposing terminals facing directly towards each other, requiring $600\,\text{mm}$ for natural draught room-sealed appliances and $1200\,\text{mm}$ for fanned draught appliances.

Dimension A (Room-Sealed Opening Below)

The minimum clearance required directly below an openable window, air brick, or door: $300\,\text{mm}$ for fanned draught; for natural draught it scales by input: $300\,\text{mm}$ ($0\text{--}7\,\text{kW}$), $600\,\text{mm}$ ($>7\text{--}14\,\text{kW}$), $1500\,\text{mm}$ ($>14\text{--}32\,\text{kW}$), and $2000\,\text{mm}$ ($>32\text{--}70\,\text{kW}$).

Dimension H

The minimum clearance from an internal or external corner, or to a boundary running alongside the terminal: $600\,\text{mm}$ for room-sealed natural draught appliances and $300\,\text{mm}$ for fanned draught appliances ($200\,\text{mm}$ for open flue fanned draught).

Dimension M and Dimension N

Separation distances between multiple terminals installed on the same wall: Dimension M requires at least $1500\,\text{mm}$ vertically, while Dimension N requires at least $300\,\text{mm}$ horizontally.

Building Extrusion Exemption ($450\,\text{mm}$ Rule)

An exception stating that corner separation distances (Dimension H) do not apply to external building extrusions not exceeding $450\,\text{mm}$ (such as disused chimney breasts on external walls) for fanned draught appliances or natural draught appliances up to $7\,\text{kW}$ net input.

End Ventilation Slate Upstand

A weatherproofing component used where a chimney passes through a roof structure, requiring an upstand of at least $150\,\text{mm}$ above the roof intersection.

Dimension L

The minimum clearance from a flue terminal to an opening into a dwelling situated inside a carport (such as a door or window), fixed at $1200\,\text{mm}$ for both fanned draught and natural draught room-sealed appliances.

Dimension D and Dimension E

Clearance distances below structural projections for fanned draught appliances: Dimension D requires $75\,\text{mm}$ below gutters, soil pipes, or drain pipes; Dimension E requires $200\,\text{mm}$ below eaves ($300\,\text{mm}$ for natural draught room-sealed).