All floor-joists are spaced 16 inches on centres, and should be bridged. The following is the table commonly followed for good house construction, although lighter work is most often specified:
| SPAN | TIMBER | |
|---|---|---|
| 12' and under | 2" × 10" | cross-bridged once. |
| 12' to 15' | 2" × 10" | doubled every other one, if good stiffness |
| is desired, and bridged twice. | ||
| 15' to 20' | 3" × 12" | and of long-leaf yellow pine, crowned at |
| centre ½", and bridged three times. | ||
| 20' to 25' | 3" × 14" | of long-leaf yellow pine, crowned at the |
| centre 1" for the 25' spans, and bridged four times. | ||
Floor-joists should be doubled around all openings larger than 3 feet, and joists should be hung from the header beam by metal straps.
There are many precautions which should be taken to prevent the spread of fire in the wooden frame house, but those will be considered as a special subject. Likewise the discussion of certain defects of construction which are commonly found in the speculative house will be dealt with later.
V
CONSTRUCTION OF THE MASONRY
AND WOOD DWELLING
In one of the previous chapters it was pointed out that the type of construction next in general use to that of the wooden frame house was the dwelling of masonry and wood. This was designated as Type II, and defined as a building with exterior walls of stone, brick, concrete, or terra-cotta, and interior floors and partitions of wooden frame construction.
The difference in construction between the wooden frame structure and the masonry-and-wood building is mostly in the material used for the exterior walls. The interiors of both types are constructed in practically the same way, the floors being of light wooden joists and the partitions of wooden studs.
The oldest varieties of the masonry houses in America are represented by the stone and brick dwellings of Colonial days. These are so substantially built, and often so artistic in conception, that they have become common models from which to draw inspiration. The concrete house of the monolithic or block type, and that of hollow terra-cotta tile, is a modern development.