Foundation Walls. 'The foundation walls of a city building above the footing course, are usually built of stone. Concrete is used to some extent, and brick will be used for the party wall where there is to be a cellar both For heavy walls of huild ings, three or more stories in height, it will be necessary to use block stone. These are stones roughly fashioned to dimension and generally laying from eighteen inches to two feet in height and the full width of the wall. (Fig. 101.) Being brought nearly even and square, not much mortar will be nse>1, and this should be of clear cement and sand below the grade line.
Rubble Walls. For a foundation of a lighter character, rubble stone may he used. This consists of stone split from a ledge with 00 preparation other than breaking up with a hammer, and squaring one edge and face. As these stones are irregular iu shape and thickness, considera ble mortar will have to he used and the character of the mortar and the filling of voids will need especial attention. An important element in the strength of a rub ble wall, is the bonding or the lapping of stones over each other.
The stones should be laid in irregular courses leveled off to a horizontal joint about every two feet, and 0 bond stone should he put in at intervals of four or five feet. Most city laws require a certain proportion of bond stones, and, if nothing is said, a through bond stone should be inserted into every five or six square feet. Care must be taken that the stones are bonded also in the direction of the length of the so that no vertical joints may appear running through three or four courses. Outside of the bonding, the manner of laying the stones must have our attention. All the stones must be laid as nearly as possible on their natural bed, that is, with their splitting snrfiiee horizontal. Angles and corners must be carefully laid with large stones hording across each yaw, as in Fig. With a heavy foundation wall of block stones, where each stone is of the full thickness Of the the main care will he to obtain a good bond, with level and plumb joints. Openings for pipes should be left when the wall is being built, as it may be difficult to break an opening after the walls are carried lib.
Derrick Stones. .11I of the stones which are suitable for the heavy walls which we have described should be large, and will require the use of derricks in handling. If the building is to he one of great size or height, a system of three or four large derricks will probably have heen started, .swinging from some central scaffold, and guyed to this and to each other. For a building of but three or four stories however, the builder would probably use a series of smaller derricks supported each by its own guy ropes. The super intendent should make sure that the ropes are strong and not frayed out, that the mast and boom are neither cracked nor sprung, and that the running gear is strong and shipshape_ The securing of the ropes is a very important matter, and should be noted by the superintendent. Although it belongs to the contractor to do this, a careful inspection by the architect will doubly insure the safety of all concerned. In suburban or out-of-town work the guys will usually be secured to a convenient tree, and this should be a young or evidently sound tree, or if posts have to be put down, as will be necessary in the city, they should be set deep in the ground with the earth well tamped in again. The guys must. he at all times drawn taut, as a loose gny A-ill be given a sudden and dangerous strain if a heavy stone is swung wound so as to bring its weight upon it.
'Ile derrick will allow of heavy atones being carefully set, and his will be especially noted in the handling of the capstones for the piles. These will have been selected for an even bed and can be shifted they rest immovable 011 the piles. In bedding, the heavy stones may be held suspended over the place where they are to lie while an even bed is being prepared, and, if neces sary, the stone may he lowered and then raised again before the final setting, so that the impression will show where the bed will need fitting.
Thickness of Walls. The thickness
of foundation walls in all large cities is
controlled by lacy, and in general will
quire that walls to a depth of ten or twelve
feet below the ground shall be four inches
thicker than the wall above, for brick, and
eight inches for stone, with an increase of
four inches for every ten feet below this. lu clay, which is more
seriously- affected by frost than gravel, it is a good plan to build
foundations with it batter on the outside of six to twelve inches, as in
Fig. 1(1:1, so that any movement. of the earth will readily free itself from
the wall, which should he made smooth on the outside Nvith cement.
Areas and Vaults. .Areas are often required, to give light
or access to basements, and these will need a retaining wall to keep
back the earth. -tone should be used for
of any Size,
The space under the sidewalks and entrance steps or porches is often utilized for coal or general storage purposes. This requires a wall at the street line which shall he heavy enough to sustain the pressure of the street and the weight of the sidewalk. If it is possible to divide this space so that the partition walls can be run back to the main building about every ten feet, the construction can be sim plified, but if an open space is required, a very heavy wall must be built at the street line, and steel beams laid from this wall to the building which will buttress the top of the street wall and support the weight of the sidewalk as well.
Brick arches may be turned be tween these beams and leveled tip for the sidewalk, or a concrete or flagstone sidewalk may he constructed over them. (Fig. 104.) If brick arches are turned, to be covered with an ordinary brick paying, the top of the arch should be coated with hot asphalt. Any of the modern forms of fireproof floor construction may be used for the sidewalk , finished with concrete or "granolithic" surface.
Dampness. As a protection against dampness, the outside of all cellar and vault walls in wet situations, should be coated with hot asphalt or Portland cement. Asphalt, applied while boiling hot in two or more coats from top to bottom, is considered the most lasting, if the ground is very damp, as Portland cement is affected by frost and is easily cracked by settlement of the walls, while asphalt, having considerable elasticity, remains sound and tight. Coal tar is sometimes used, but will gradually become brittle and crumble away.