Surveys are carried out on the external wall constructions in buildings either with a specific concern, or buildings with a height of 18 metres or more above ground level
Cynhelir arolygon ar waith adeiladu’r waliau allanol mewn adeiladau a chanddynt naill ai pryder penodol, neu adeiladau sydd ag uchder o 18 metr neu fwy uwchben lefel y ddaear.