Solarium may refer to: Sunroom, a room built largely of glass to afford exposure to the sun. A Terrace (building) or flat housetop. The Solarium Augusti, a monumental meridian line (or perhaps a sundial) erected in Rome by Emperor Augustus.
Noun. 1. cavity wall-a wall formed of two thicknesses of masonry with a space between them. wall-an architectural partition with a height and length greater than its thickness; used to divide or enclose an area or to support another structure; the south wall had a small window; the walls were covered with pictures.
Cavity walls consist of two 'skins' separated by a hollow space (cavity). The skins are commonly masonry such as brick or concrete block. Masonry is an absorbent material, and therefore will slowly draw rainwater or even humidity into the wall, as well as from the inside of the house as from outside.