Gas pipe through a wall or cavity: the rules
Yes, in effect. Regulation 19(2) lets gas pipework pass through a wall only by the shortest practicable route, with adequate means to stop escaping gas entering any cavity. HSE's guidance says that may be a gas-tight sleeve ventilated to a safe position. Pipework may not run along inside a cavity, bar one fire exception.
Reviewed by Jordan Valentine-Dunn, Gas Safe registered engineer · Portsmouth Gas Heating · Last reviewed October 2026
A gas pipe through a cavity wall must take the shortest route and be sleeved so that a leak cannot collect in the cavity. Regulation 19 of the Gas Safety (Installation and Use) Regulations 1998 sets that rule, and the five others below it, for pipework in walls, floors, cavities, foundations and voids.
What does regulation 19 say about gas pipes in walls, cavities and voids?
Regulation 19 is headed Enclosed pipes. It applies to installation pipework, the pipe downstream of the meter, and each of its six paragraphs governs a different place the pipe can go. Paragraph 5 also covers service pipework, the pipe from the main to the meter.
| Where the pipe goes | What the regulation requires | Regulation |
|---|---|---|
| In a wall, floor or standing of solid construction | Constructed and installed so it is protected against failure caused by movement of the wall, floor or standing | 19(1) |
| Through a wall, floor or standing of solid construction, side to side, whether or not it contains a cavity | The part within the wall takes the shortest practicable route, and adequate means are provided to prevent, so far as reasonably practicable, escaping gas entering any cavity | 19(2) |
| In the cavity of a cavity wall | Not allowed, unless the pipe is passing through the wall from one side to the other | 19(3) |
| In the cavity, for a living flame effect fire | Allowed if the pipe in the cavity is as short as reasonably practicable, enclosed in a gas-tight sleeve and sealed where it enters the fire; the fire must be fanned-flue, simulate a solid fuel fire and sit in the inner leaf | 19(4) |
| Under the foundations of a building, or under the base of a wall or footings | Adequate steps taken to prevent damage if those structures or the ground move; applies to service pipework too | 19(5) |
| In a shaft, duct or void | Not unless it is adequately ventilated, except where the pipe is itself inside a ventilated duct | 19(6) |
The regulation names no material, sleeve size or distance. How to achieve each requirement is left to the appropriate standard, which HSE's guidance on 19(1) points to without naming the clauses. The pipework standard, BS 6891, is a paid document, so this page quotes no figure from it.
Does a gas pipe need to be sleeved through a wall?
The regulation asks for adequate means to stop escaping gas entering the cavity, and HSE's L56 guidance paragraph 209 says what that may be: the part of the pipe that passes through enclosed in a gas-tight sleeve, which is itself ventilated to a safe position, preferably open air. The gap between pipe and sleeve is sealed at one end only, so a leak cannot collect in it.
| Point | What L56 says | Effect |
|---|---|---|
| The risk | Leakage from pipework within a cavity may be difficult to detect and readily lead to an explosive gas and air mixture | The reason the cavity is the concern, not the wall itself |
| The measure | Enclose the part of the pipe that passes through in a gas-tight sleeve ventilated to a safe position, preferably open air | Any leak is carried outside |
| The seal | Seal the gap between pipe and sleeve with fire-retardant flexible sealant, at one end only | A leak cannot accumulate in the gap |
| The side benefit | Some protection against mechanical damage, such as structural movement | Links to regulation 19(5) and 19(1) |
Can a gas pipe run inside a cavity wall?
No, except to pass through it. Regulation 19(3) bars any part of the pipe lying in the cavity of a cavity wall unless it crosses from one side to the other. Paragraph 19(4) makes one exception: pipework to a living flame effect fire that is fanned-flue and sits in the inner leaf, in a gas-tight sleeve, as short as reasonably practicable.
Can gas pipes be chased into walls?
Regulation 19(1) covers pipe in a wall of solid construction and asks that it is protected against failure caused by the wall moving. It does not say whether a pipe may be chased in or how. HSE's guidance on 19(1) sends the reader to the appropriate standard, and the standard is where a chasing method has to be checked.
What does regulation 7 add about protecting the pipe?
Regulation 7(1) says a gas fitting must be properly supported and placed or protected so as to avoid undue risk of damage. L56 paragraph 135 adds that the fitting should be supported so no undue strain falls on it and, as far as possible, kept out of the way of foreseeable activities nearby. Where that cannot be avoided, it should be protected.
Where can a gas pipe go in a void or duct?
Only in a shaft, duct or void that is adequately ventilated, unless the pipe is itself inside a ventilated duct (regulation 19(6)). L56 paragraph 211 adds that for LPG, which is heavier than air, cellars, basements and unventilated suspended floors all count as voids. Ventilating a duct must not impair fire or smoke separation (regulation 20).
- Worked example 1: a new boiler on an outside wall of a cavity-wall house. The pipe goes through the wall on the shortest practicable route, so 19(2)(a) is met. Inside the wall it is enclosed in a gas-tight sleeve vented to open air, which is the measure L56 paragraph 209 describes for 19(2)(b), and the pipe does not run along the cavity, so 19(3) is met.
- Worked example 2: a pipe to a fanned-flue living flame effect fire in the inner leaf. Regulation 19(4) lets the pipe lie in the cavity, but only as far as it must, in a gas-tight sleeve sealed at the fire. If the same fire were natural draught, the exception would not apply and 19(3) would bar the pipe from the cavity.
Only a Gas Safe registered engineer can install, test, service or certify gas pipework, and the choice of sleeve, route and method is theirs. This page sets out what regulation 19, regulation 7 and HSE's guidance say; the standard and the appliance maker's instructions decide how the work is done.
If you smell gas, call National Gas on 0800 111 999, free, at any hour. On a Manifold gas safety check the tightness test card works from the IGEM/UP/1B tables and the result prints on the record.
Frequently asked
Sources
- Legislation.gov.uk, Gas Safety (Installation and Use) Regulations 1998, regulation 19
- Legislation.gov.uk, Gas Safety (Installation and Use) Regulations 1998, regulation 7
- HSE, L56 Safety in the installation and use of gas systems and appliances (fifth edition, 2018), regulations 7 and 19
- National Gas, emergency contacts
Related guides
Last reviewed October 2026. This guide is general information, not legal or safety advice, gas safety work must be carried out by an appropriately Gas Safe registered engineer. Rules can change, so check the linked official sources for the current position.