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.
_Platform-Frame_
[Illustration: PLATFORM FRAME]
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.
[Illustration: CLAPBOARDS OVER WOODEN STUDS]
_Features Common to All_
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.
[Illustration: 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: