Cement based renders and mortars are unsuitable for use on historic properties as they inhibit the movement of moisture which can lead to damp, rot and decay.
Mae rendradau a morterau sy'n cynnwys sment yn anaddas i'w defnyddio ar eiddo hanesyddol gan eu bod yn atal gwlybaniaeth rhag symud a gall hyn arwain at leithder, pydredd a dadfeilio.