A very bad method of constructing a chimney was imported from Europe, years ago, which develops serious fire dangers from its manner of settling. Instead of flashing and counter-flashing the joint of the chimney with the roof, this method employed the use of a projecting course of brick begun at the level of the roof. Thus the part of the chimney above the shingle roof was made larger than that underneath, and the outward step was used as a weather lap over the roofing material, and no flashing was needed to make the joint tight. Now, when the chimney settled faster than the roof, as it would, the upper part could not drop, but was caught upon the roof, and lifted from the lower part. This made a crack through which the hot gases could escape to the attic timbers and start a fire.
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.
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.