STONELAYING is the process of laying up or joining together stone to form stonework. Stone work in buildings includes walls, piers, arches, and trimmings. Walls are generally either rub ble or ashlar stonework. Rubble stonework is in general used only for foundation walls and for exterior walls—I I I when suitable stone for cut ting cannot be obtained. (2) when the expense of cut stone is not warranted, and (3) when a rus tic appearance is desired by the architect. In laying rubble walls I Fig. I) the rough projec tions 011 the stones as they collie in various sizes from the quarry are broken oil'. The stonelayer then places the stones in the \•an, choosing and alternating the large and small stones so that they will fit together as compactly or with as few void spaces as possible, so that the front and back of the wall is well tied or bonded together, and so that the exposed face of the wall shall present the neatest possible appearance. All void spaces are packed with spans or stone chips and Hushed full of mortar. Mortar is also placed between the stones, so that they do not touch them, and as fast as the facing is carried up it i., followed by the supporting rubble or brickwork backing. At intervals a facing-stone of unusual depth is inserted, which extends back into the backing and ties the facing to the backing. Sometimes metal ties are used in place of deeper facing-stones to insure this bonding together of the wall. The arrangement of the stones com posing the ashlar facing, or, so to speak, the each other, but are held together by the hardened matrix. :111 rubble stonework is built substan tially as described. except in some eases the face stones have their joints dressed (Fig. 2) so that when laid up the face of the wall has a mosaic like appearance. while in other eases round field stones or cobblestones are used for the facing. Ashlar stonework, or stonework of rectangular cut stone (Figs. 3 and 4), is used for walls in which the solidity and regularity is desired that is given only by stones cut and dressed to perfect parallelopipedons. Walls are seldom built of ashlar cut stone for their whole thickness, but are composed of an ashlar facing, backed by rubble stonework or by brickwork.
pattern of the facing, is specified by the architect so that the stonelayer has only to follow these instructions.
After the wall, including facing and backing, has been completed, the stonelayer serapes out and removes the mortar joints to the depth of about one inch, and fills the spec thus secured with finer quality of mortar, giving it a rounded edge or beading. This work is termed pointing. After the pointing has been completed long enough for the wall to become hard, the face of thewnll is cleaned or scrubbed with water and mu riatie acid, which completes the work. This work
is termed cleaning. A rches are almost always built of cut and dressed stones (Fig. 5), having In laying ashlar facing, the stonelayer super imposes one stone upon another side by side, or end to end, with thin mortar joints latween the shape of the frustum of a wedge, and called voussoirs. (See Ascii.) Rubble arches are sometimes used, but they require the selection of suitably shaped stones for mussoirs, and the use of wedge-shaped mortar joints. In cut-stone arches nearly always an odd number of voussoirs are used, so that one of them, called a keystone, comes exactly at the centre of the top of the arch.
In laying stone arches, the stonelayer first erects a centre (Fig. 6), which is a structure of wood or iron whose top surface constitutes a platform eurved to the exact arc of the intrados of the arch. Work is then begun by laying the bottom voussoir on eaeh side of the arch. The succeeding voussoirs are then laid, one after an ..
other, working from both sides toward the top, and finally the top voussoir, or keystone. is in serted. Between the voussoirs are mortar joints. Until the keystone is inserted. the support of the centre is absolutely necessary to keep the arch from falling, and as a matter of fact it is usually left standing for some time after the keystone is in place, so that the mortar joints may harden before the strain of supporting itself is put upon the arch by removing its cen tre.
Arches in building are constructed in a va riety of styles. flat (Fig. 7), elliptical, pointed, polycentrie, etc., but all styles are laid up ex actly in the way described above. I'iers in build ing are column-like structures, used mostly as intermediate supports for interior columns or for girders. They are built of both rubble and cut stone, but more commonly of brick. In lay ing stone piers, the mode of procedure is prac tically the same as in laying walls. Trimmings in building usually denote all moldings, caps, sills, cornices, lintels. etc. Such pieces are usu ally cut and dressed to form and dimensions ac cording to the architect's drawing, and are fur nished to the stonelayer ready to set in place. In laying trimming; the stonclayer has. there fore, only to place them in their designated po sition, with suitable mortar joints, and to bind them to the adjoining walls. Arch rings and trimmings are often ornamented by stone-cut ting, and frequently this work is done after they arc set in place in the building. See SToxE CUTTI NO ; SCULPTURE ; MASON HY ; CEMENT; FouxnaTioxs: and BultDING-ST0NEs.