As the title suggests is it a legal requirement under the Gas Safety (Installation and Use) Regulations 1998 if so which part please. Thanks

Many thanks

Thanks Ron, I also see section 24 Part B mentions it in the regulations; s24 (b) of the The Gas Safety (Installation and Use) Regulations 1998 does make mention of having a line diagram for premises that have a gas supply of 50mm and above: "24.—(1) Where the service pipe to any building having two or more floors to which gas is supplied or (whether or not it has more than one floor) a floor having areas with a separate supply of gas has an internal diameter of 50 mm or more, no person shall install any incoming installation pipework supplying gas to any of those floors or areas, as the case may be, unless—" (a)a valve is installed in the pipe in a conspicuous and readily accessible position; and (b)a line diagram in permanent form is attached to the building in a readily accessible position as near as practicable to—