The outer row of stones of a wall are termed the facing; those within the filling; those at the rear the backing. A horizontal laying of either stone or bricks is a course; a sloped surface of a well is a batter; a protecting often projecting course on top is a coping. A bond is a stone going through two or more courses to bind them together ; a quoin is a squared stone at a corner; a stretcher is greatest in horizontal length, a header shortest, the latter being a bond. A cramp is a bar of iron or steel let into a wall to brace it. Ashlar are squared stone; rubble irregularly shaped stone, A corbel is a stone projecting as a balance-weight; a sill, a broad stone at the base of an opening; a template, a large stout stone for supporting the end of a girder or beam.
Ashlar The stonework of the outer face of a wall when it is cut and differs in character from the back of the wall is called ashlar. The coursing of ashlar is done in dif ferent ways. The simplest form is when it is laid out in continued courses. In this case it is caller °regular coursed ashlar? Ashlar is also laid without long horizontal joints. In this case it is called °broken ashlar" This is generally used when stone cannot be easily obtained of equal heights. It takes longer to lay this up, which makes it cost more than the regular courses, but makes a very attractive looking wall, having more freedom and texture. It is customary to cut the stone at the stone yard certain heights; for example, two, four, six and eight inches, so that they can be laid up without cutting any joint except the end joint, at the building. From three to six different heights are generally used, the larger number giving more variety than when the smaller number of sizes is used Coursed random ashlar has horizontal joints one-half to two feet apart, continuous. Between these joints the stone is laid up irregularly. The other stone on the walls of a building are called trimmings, which include the molded work, the window sills, jambs and the quoins, which are the cornerstones of the building. The quoins and jamb stones, if of the same material, may be included with the rest of the ashlar. The part of the wall back of the ashlar (called the backing) is of cheaper stone or brick. It is never under eight inches thick when of brick, and if of stone the backing is thicker. This should be built and bonded in at the same time as the ashlar in order to make a solid wall. If the stones are not high, the thickness of the ashlar should vary so that the backing can bond in and it is generally speci fied that the ashlar should include one through bond stone in every 10 square feet of wall. If the facing is thin (two inches to four inches), the pieces are clamped back into the backing by iron clamps. Random rubble is where un trimmed stones are used, and selected to fit as well as possible.
In public work and important buildings, every stone should be shown on the drawings, except when random ashlar is employed. In this case the arrangement of the stone is made by the foreman on the building, to follow a sample piece of ashlar set up and approved by the architect. Ashlar is usually from four inches to eight inches thick. In figuring the quantity an average of six inches in thickness is generally taken. The heights vary from 10 inches to 14 inches. For exterior work the ashlar should not be under four inches thick. The ashlar may be laid with V joints, or with rustication. In the latter case the face is gen erally rock-face or pointed and a draftline an inch wide is carried around the edge of the stone.
Bond stones are stones that go into the wall to hold the wall together. If there are many small stones these should be frequent. In lay ing out ashlar the bond should be arranged to give effective stone jointing. Sometimes the Flemish bond arrangement is used as in brick work. Bond stones the full size of a pier are frequently used for caps and also placed at intervals through the pier.
Bricks are laid so as to dis tribute the load and tie the different portions of the wall together. Stretchers are brick which are laid showing their long side. Head ers show the end of the bricks. Common bond is to lay the brick with stretchers for five courses and then lay headers for the sixth course. Face brick bond is as a rule laid of stretchers and bonded either by clipping the corners of the bricks, which tie the face of the wall to the backing, or with metal wall ties, which are made of wire, crimped metal or of tin fastened to steel wire. Flemish bond is the bond which is most frequently used to give an interesting wall surface, more pleasing than what is obtained with common bond. It is laid up with alternate headers and stretchers. The small piece inserted at the corners is called a closer. English bond consists of courses of headers and stretchers alternating. A variety of this, called English cross bond, has the alter nate courses of stretchers arranged with the joints below the middle of the bricks above, making a figure resembling a cross. Some times every fifth course of brick is laid Flem ish bond with the others straight bond. Every fifth course may be set in or back an inch, forming rusticated work. When walls have hollow or °vaulted" spaces not over two inches wide in the centre the bond is made by bricks laid across the space and cut in diagonally, or by the use of metal ties every four to eight courses. In arches, the face of the arch is made with the same bond as that shown on the wall. Common arches are made with succes sive rings or rowlocks, of headers.