This section is from the book "The Principles And Practice Of Modern House-Construction", by G. Lister Sutcliffe. Also available from Amazon: How Your House Works: A Visual Guide to Understanding & Maintaining Your Home.
The soaking of rain into walls may be very largely prevented by various little devices, by means of which the rain blown against the walls is diverted from its course down the walls and thrown clear of the building.
Moulded string-courses, as in Fig. 59, will fulfil the purpose, a is a brick section which would have been all the better if the top bed from x to y had been weathered; it will be noticed that the upper bed of the stone mould at B is shown sharply weathered, so that the water is not conducted into the wall, and that the under surface of the nose at z is sloped upwards in order that the water may drop freely from the edge instead of following the curve of the mould. The undercut cornice shown at c forms an effectual drip. Moulded string-courses, therefore, are not mere ornamental superfluities; they are ornamental, but they are also useful. A cornice or label mould over a window keeps the window drier.
Fig. 59-Moulded String -courses.
Rain caught on windows should be thrown by the window-sills quite clear of the walls below; in other words, the sills must project, and they are all the better if throated also. A weathered and throated stone sill is shown at l in Fig. 18, page 56. Fig. 60 gives two brick sills made by the Rowlands Castle Brick and Tile Co.; the throating under the sill a is a great improvement. Sills flush with the wall should not be tolerated, unless there is a moulded string-course under them, which will act as a drip. Sill-bricks should be dense and hard, - blue Staffordshire being the best, - and should be set in good cementmortar.
Parapets are often the cause of damp walls. They may with advantage be built with cement-mortar, and the coping should be throated and weathered. Stone coping is shown in Plate III., and Fig. 61 gives two good forms of brick coping. All parapet copings should be laid in cement-mortar, and the stone coping is all the better if the joints are joggled, as shown in Fig. 62. Under all parapets an asphalt damp-course should be formed, as already explained and illustrated.
In half-timber work, and in tile-hung walls, the same principles must be borne in mind respecting the projection of sills and the section of moulds.
Projecting eaves and gables contribute largely to the dryness of the walls below.
Fig. 60. - Moulded Brick sills..
Fig. 61.-Brick Coping.
Fig. 62 - Joggled Joint in Stone Coping.