If no other cause for damp on the inner face of a cavity wall can be identified, it may be the result of builders’ debris trapped between the two brick skins.
Os na ellir nodi unrhyw reswm arall dros leithder ar wyneb mewnol wal geudod, efallai fod sbwriel adeiladwyr wedi'i ddal rhwng y ddwy haen o frics.