Mae’r canllawiau (Cylchlythrau’r Swyddfa Gymreig 61/96 a 1/98) sy’n ategu’r ddeddfwriaeth yn esbonio’r meini prawf a ddefnyddir i asesu adeiladau. Mae’r meini prawf ar gyfer rhestru adeiladau yn esbonio’r prif ffactorau y dylid rhoi sylw iddynt wrth ystyried cais i restru adeilad. Er enghraifft, gellir ystyried rhestru adeilad ar sail diddordeb pensaernïol os bernir bod ei gynllun pensaernïol, ei grefftwaith a’r modd y mae wedi’i addurno o bwysigrwydd cenedlaethol.
The legislation is supported by guidance (Wales Office Circulars 61/96 and 1/98) which explains the criteria against which candidate buildings will be assessed. The listing criteria explains the principal factors to be taken into account when considering a listing request. For example, a building might be considered for an Architectural interest listing if it is deemed as being nationally important for its architectural design, decoration, and craftsmanship.