There are no sharp distinctions between the various types of wooden frame construction. But in order to classify certain tendencies, we will arbitrarily define four types. To these we will give the names of braced-frame, balloon-frame, combination-frame, and platform-frame.
The braced-frame is the oldest type, and originated in Colonial days in New England. It was developed under the influence of a tradition of heavy, European half-timber construction, and also nourished by the abundance of wood directly at hand. The fact that nails were not made, except by hand, urged the carpenters to use methods of fastening which required as few as possible. Because of these factors, then, certain definite characteristics of this type of wooden frame construction manifest themselves in the use of timbers, far larger than necessary for safety, and joints consisting of mortises and tenons.
As the sawmill became mechanically more rapid, and as nails were being turned out by machines more plentifully, the Yankee who went West on adventuresome trips, and cared little for a permanent dwelling, devised a system of light-frame construction which became known as the balloon-frame. This was put together with the greatest speed, and required only nails for fastening all joints. The timbers which were used were standardized to one size, namely, 2 inches by 4 inches.
CORNER CONSTRUCTION OF BRACED-FRAME
MORTICE & TENON JOINTS
Now, both of these types had advantages and disadvantages which were bound to influence later builders. Those who had been accustomed to build according to the braced-frame system found that lumber was becoming scarcer, and that nails were cheaper than they formerly were. Certain features of the balloon-frame appealed to them, such as its greater speed of construction, its smaller timbers, and lightness. On the other hand, those people who had lived in houses constructed according to the balloon system of framing found that they were very flimsy, that fires quickly consumed them, that rats and vermin could travel freely through the walls, and that, after all, they were only the most temporary sort of shelter. These folks looked back at the old methods of building, and saw the good features of solidity and permanence. We had, therefore, the growing together of the two systems of construction into a type which we call the combination-frame dwelling.
However, progress did not stop at this point. The houses built according to this newly devised system were found to settle unevenly, which cracked plaster ceilings and walls and made doors and windows into leaning parallelograms. The cause of this was found to be due to the natural shrinkage of wood as it dried out. Now, all wood shrinks mostly across the grain, and not with it, so that the amount of settlement of any wooden wall depends upon the amount of cross-section of wood which it contains. If there is more in the interior partitions than in the exterior, it is certain that the floor-joists will settle down on the inside ends more than the outside. This is exactly what happened. It occurred not only in the combination-frame but in the braced and balloon frame. Various devices were introduced to avoid this defect, but all were more or less incomplete. Nevertheless, it all led gradually to the development of the fourth type of construction, which is called the platform-frame, for lack of a better name. This frame solves the problem of uneven settlement in the wooden structure. It also makes the location of the windows of the second floor independent of those of the first floor, which is not the case with the balloon-frame, for in this type the studs extend in one piece from the sill to the plate, requiring the centring of the windows of the second floor over those on the first.
The methods which are used in constructing the small house of to-day are not as simply classified as the previous description would lead one to believe. The old New England braced-frame has practically gone out of existence, yet many of its features remain. The balloon-frame is used only in the cheapest sort of structures, yet many of its details are found in the modern dwelling; The combination-frame in all its many varied forms can be called the advanced type.
The illustrations show the four types in their entirety. But in order to fully understand the combination-frame, it is necessary to know what features of the braced-frame and balloon-frame are used to-day.
1. The use of the girt, because it permits the location of the second-floor windows at any point irrespective of the first floor windows. This cannot be done when a ribbon-board is used, for this requires studs which extend continuously from sill to plate, and if any windows are to be located on the second floor, they must be placed directly over those on the first floor. The ribbon-board does not act as a stop for either vermin or fire, as does the girt. However, fire-stops can be introduced in connection with the ribbon-board, if the extra expense is no hindrance.
2. The use of the sill, because it serves as a firm foundation for the outside studs and first tier of floor-joists. The balloon-frame has no sill, for the floor-joists are set directly upon the top of the foundation-wall, and the exterior studs are built on top of them.
3. The use of the corner braces, because they stiffen the frame.
TYPICAL FRAMING OF “WAR HOUSES.”
1. The use of small timbers, or the standardization of the 2 by 4 for all parts except the sill, because of economy. The corner-posts are made of three 2 by 4’s, and the plate is made of two 2 by 4’s.
2. The use of the nailed joint, because of its cheapness and its greater strength. It will not rattle loose when the timber seasons, as does the mortise and tenon joint in the braced-frame.
3. The use of the ribbon-board, in place of the girt, for those houses which are to be stuccoed, and a rigid, outside wall-frame is desired from sill to plate.
4. The use of diagonal sheathing-boards, to brace the frame instead of the corner-pieces. The reasons for this are not very certain, since diagonal bracing with sheathing is not always effective, while it is extremely wasteful.
The combination-frame includes all of the present-day methods which make use of selected features of both the braced-frame and balloon-frame, such as were noted above. There are no rules to follow. In certain sections of the country one type is favored more than the other. Where a house is to be covered with stucco, the balloon-frame is a better type to use than the braced-frame, since it gives a stiffer outside wall as a backing for the stucco.
It will be noticed in the illustration how different is the amount of cross-section of wood in exterior and interior walls of the combination-frame, a thing which causes the unequal settlement previously alluded to. In order to reduce this to a minimum, it is often specified that the studs of all interior partitions be carried down to the top of the cap of the partition below or to the top of the supporting girder, thus reducing the amount of cross-section timber. This is not a complete cure, however, although it is a big improvement.
The real solution of the difficulty lies in the use of the platform system of construction. In this system the first floor is built on top of the foundation-walls, as though it were a platform. A sill, called the box-sill, is constructed for the exterior support of the ends of the floor-joists by laying down a timber the same size as the joists and setting another one on the extreme edge in a vertical position. The angle thus formed makes a resting-box into which the floor-joist can be framed. The interior ends of the floor-joists should be supported upon a steel I-beam upon which has been placed a 2-inch-thick timber. The I-beam should be supported upon steel-tube columns which have been filled with concrete. On top of the floor-joists should be nailed the underflooring, laid diagonally. The first floor then appears as a perfectly smooth platform. Now wherever there is to be erected an interior or exterior partition, a 2 by 4, called the sole piece, is nailed directly on top of the rough flooring. This serves as a sill for the studs of the partition, which are now erected vertically upon them and capped with double 2 by 4’s on the top. Now the second floor is built on top of the partitions in the same manner as the first, and a new platform is constructed, so to speak. Upon this is then erected the partitions of the second floor, and on this the floor of the attic. In fact, this construction proceeds floor by floor, and each floor is an independent platform. If the drawings are examined it will be noticed that the amount of cross-section of wood in any one bearing partition is identically the same as in any other. The dwelling built in this way, then, cannot settle unevenly, and the cracked plaster and twisted doors will be eliminated.
CLAPBOARDS OVER WOODEN STUDS
There are certain features which are common to all types of frames. For instance, the framing around all doors and windows requires the use of double 2 by 4’s or the use of one 4 by 4.
These framing studs around the window are set 5 inches higher and 8 inches wider than the dimensions of the finished window. Those about the door-openings are set 2 inches higher and 4 inches wider.
BRICK VENEER OVER WOODEN STUDS.
All use sheathing-boards of ⅞-inch stock to cover the outside of the studs, and these are usually 6 inches to 8 inches wide.
The usual spacing of studs is 16 inches on centres, and they are generally of 2 by 4’s, although where any pipes or flues are run through the partition they should be 2 by 6’s.
Interior stud partitions should be bridged or braced once in their height, and partitions which run parallel to the floor-joists should have a capping-board, so that the proper nailing for lath can be secured. In fact, at all intersections of partitions care should be exercised that the required nailing for lath is provided.
In the construction of roofs the average spacing of rafters is 20 inches on centres. They should be doubled around all openings. The ridge is usually of a 1-inch by 10-inch piece. The size of the rafters varies with the length of span and load. They are usually 2 inches by 6 inches for short spans and light loads, and 2 inches by 8 inches or 2 inches by 10 inches for long spans and comparatively heavy loads. Valley rafters must always be deeper and heavier than the rafters and should be designed as a girder. The hip rafters do not carry any great load, but are often made deeper to fit the incline cut of the jack rafters.
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.