If a new room is being created as a result of the addition of an internal wall then care should also be taken to ensure that the existing room is ventilated adequately.
Os caiff y cnwd ei bori, dylid rheoli’r pori hwnnw fel nad oes pridd yn cael ei olchi i ffwrdd yn ystod y cyfnod rhwng y pori a sefydlu’r cnwd dilynol.