On the other hand, wooden framed walls will settle badly, too, when dry rot sets into the sills. This is a very common defect in old houses, and generally, when any remodelling must be done, the sills have to be cut out and new ones set into place. Dry rot in the sills is caused by excessive dampness with no circulation of air. Very often a builder may take great pains to fire-stop his walls around the sill, but forget to leave ventilation space, and the sill is soon attacked by the fungus of rot. Unless timbers which come in contact with masonry are treated with creosote, or painted, they will be subject to dry rot in the average damp, warm climate. [Illustration: Solid Column] Many porch columns rot at their base and permit the settling of the roof. Solid columns are the least durable in this respect, for in a short time their core will go bad and the lower part will crumble. Wood base blocks for columns should be perforated with holes to permit the seepage of water under them. Cast-iron bases are preferred to the wooden one, when the column is to set upon a masonry porch floor. Settling causes many other defects besides those mentioned. The house-drain may be broken and the cellar flooded with sewage, if the wall around the pipe has been cemented up and it settles. The pitch of drain-pipes may be altered so much that back-up action of waste water may occur; steps may be caused to sag so that they become unsafe; lintels may be broken. The movement of the footings by frost is another evil that is noticeable in many old houses. Sidewalks are cracked, porch stairs loosened, drains in areas closed. In most cases like this the footings are not extended far enough below the frost-line, or insufficient cinder foundations are laid. [Illustration: Weathered Chimney] But the action of freezing water leaves its marks on other parts of the house. Unless some corrugations in leaders are made, the ice in the winter may burst them. The mortar on copings is loosened by this action, and on chimney tops, where heat and gases also help, the brickwork soon breaks down. Many failures of stucco work are directly caused by frost, and sometimes water leaks into the cells of hollow terra-cotta blocks, freezes, and bursts out the shell-like sides. The putty around the window is loosened by the drying action of the wind, and the prying action of the frost. Water-supply pipes in wall near the outside are broken when the cold winds freeze them, and the exposed gas-pipes in the chilly parts of the cellar are often entirely clogged in a severe winter. Leaks around windows in masonry walls are started by frost, and it is common to see tile on the porch floor, or brick borders and bases loosened by the same powerful agent that breaks boulders from the mountainsides.