‹‹‹ Vitr. 7.3.11 | Table of Contents | Vitr. 7.4.2 ›››
4I have explained how plastering is executed in dry situations; now I shall give directions for it, that it may be durable in those that are damp. First, in apartments on the ground-floor; a height of three feet from the pavement is to have its first coat of potsherds, instead of sand, so that this part of the plastering may not be injured by the damp. But if a wall is liable to continual moisture, another thin wall should be carried up inside it, as far within as the case will admit; and between the two walls a cavity is to be left lower than the level of the floor of the apartment, with openings for air. At the upper part, also, openings must be left; for if the damp do not evaporate through these holes above and below, it will extend to the new work. The wall is then to be plastered with the potsherd mortar, made smooth, and then polished with the last coat.
4Having spoken of the method by which stucco work should be done in dry situations, I shall next explain how the polished finish is to be accomplished in places that are damp, in such a way that it can last without defects. First, in apartments which are level with the ground, apply a rendering coat of mortar, mixed with burnt brick instead of sand, to a height of about three feet above the floor, and then lay on the stucco so that those portions of it may not be injured by the dampness. But if a wall is in a state of dampness all over, construct a second thin wall a little way from it on the inside, at a distance suited to circumstances, and in the space between these two walls run a channel, at a lower level than that of the apartment, with vents to the open air. Similarly, when the wall is brought up to the top, leave airholes there. For if the moisture has no means of getting out by vents at the bottom and at the top, it will not fail to spread all over the new wall. This done, apply a rendering coat of mortar made with burnt brick to this wall, spread on the layer of stucco, and polish it.