process, all water having been expelled, there is a consequent shrinkage in the size of the pieces-practically 1 in. in 1 ft.-allowance for which is made by a terra cotta draftsman who must necessarily redraw all architectural scale or full size details at what is known as the "shrinkage scale" of 13 in. to the foot.

165. Assembling. Before shipping the terra cotta to the work, each piece is numbered and carefully fitted. The fitting operation consists in placing the various pieces in the relative positions which they would have in the building and then trimming the joints where necessary so that the pieces will all fit accurately together. By the use of a rubbing bed the joints may be rubbed to an absolutely straight line, in the same manner that stone is rubbed. The rubbing of the joints is a great advantage where absolute alignment of the pieces is especially desired, and is most frequently required for work in connection with entrances and lower

FIG. 60.-Examples of jointing in columns and bases. Notes on sizes of pieces.

stories. For work at a height of 30 ft. or more above grade, the rubbing of joints is usually regarded as an unnecessary expense. Rubbed joints should be uniformly true and not less than in. nor more than 346 in. wide. Other joints should be carefully fitted and should not be less than 14 in. nor more than 3% in. wide.

The numbering operation consists in marking each piece to correspond with a number placed on the setting drawings, full and complete sets of which are furnished by the manufacturer. Setting drawings show the size of joints to be used for the various portions of the work and the position of each block in the building.

166. Protection in Shipping.-After numbering, the work is ready for delivery and is shipped to the building. In shipping terra cotta, each piece should be carefully packed in hay or straw; and ornamental or projecting members should in addition be protected by boxing or crating, The same care should be exercised if the material is stored at the site.

167. Sizes and Characteristics.-Terra cotta is usually made in blocks 24 to 30 in. long and of a height less than this, the exact height determined by the character of the work. Owing to the tendency of large clay products to warp in burning, extremely large blocks are difficult to obtain in true alignment of surface. All pieces should be of sufficient depth to properly tie into the backing. About 4 in. is required for ashlar work and for slight projections. For greater projections the block should be sufficiently deep to be self-supporting or should be properly secured by anchors.

The front of raised joints may be cut back thus

Rectangular Raised Joint

T

Oval Raised Joint

FIG. 61.-Two methods of making raised joints on sloping surfaces.

To save material and weight and to lessen the tendency to warping, blocks are formed of an outer shell connected and braced by partitions or webs. These webs are usually arranged so that the spaces do not exceed 6 in. The outside shells and the partitions should be of uniform thickness, ranging from 1 in. in small pieces to 11⁄2 in. in large pieces.

Terra cotta should be well burned; should give a sharp metallic ring when struck; and sample or test pieces broken in two should show a uniform fracture and no air-holes in spots. The body should be hard enough to resist scratching with steel, should be free from fire or body cracks that would impair its strength or durability and the blocks should not be badly warped or twisted. Columns, cornices, moldings, etc., should be reasonably straight and true, and free from irregular or wavy lines. Examples of jointing, notes on sizes, and sections showing the webs in cylindrical columns (and base) are illustrated (see Fig. 60).

168. Surface, Finish, and Color.-Up to about 30 yr. ago, terra cotta was made in but two colors-unglazed red and unglazed buff-the red being the more widely used, matching the red brick with which it was then most frequently used. At the present time, while the body of all good terra cotta is very much the same, by surface treatment practicaly every color that could be wanted in architectural work can be obtained. Terra cotta can be made similar in color and texture to the various building stones, shafts of stone columns being frequently fitted with ornamental caps of terra cotta. Unless the terra cotta, however, is ornamental or the surface prominently molded, it should not be used to match up to or imitate adjoining stone work, for the two materials will weather differently. Preferably, each should be so designed and used as to preserve its own identity.

While terra cotta may be manufactured in practically any surface texture or finish desired, the usual surface treatments, irrespective of color, are known as Standard, Granite and Glazed. The usual colors and finishes manufactured are as follows: Standard Finish.-A dull finish similar to dressed limestone and made in various shades of buff, gray, salmon, red, and brown. Most surfaces thus produced are vitreous. Granite Finish (Standard). A mottled surface on standard terra cotta producing a granite effect. Glazed Matt Finish.-An enameled porcelain surface-imperviousin various colors. Faience colors are almost invariably matt finish. Glazed Lustrous Finish.-An enameled porcelain surface with high gloss-impervious -usually made in white and cream shades. Glazed Granite Finish-A mottled surface covered with enamel of high quality. Either lustrous (a polished granite effect) or matt.

Raised joint dies on
wash at frame
line

Sill with water bar

FIG. 62.-Details of sill construction with raised joints and fillets.

The different colors and finishes increase in cost in the following order: (1) Standard finish, plain colors; (2) Standard finish, granites; (3) Glazed, mottled and granite effects; (4) Glazed, matt finish; (5) Glazed, lustrous finish; (6) Glazed, gold or silver; (7) Glazed, reds.

169. Washes, Flashings, Anchors, Hangers, Etc.-All sills, copings, washes inside of the wall line, and all washes more than 4 in. wide on projecting members should have raised filleted horizontal joints (see Fig. 61). Sills should have a raised fillet at the back to be let into a groove in the wooden sill or should have raglet for metal water bar (see Fig. 62). Ornamental work, where, on account of the character of the detail, pockets are formed in which snow or ice can collect, should be provided with holes or washes for drainage. Copings, sills, and projecting members generally should be provided with drips, and cornices with weep holes wherever necessary.

Wide flat washes in terra cotta, where it is impractical to use either a sufficiently steep

pitch for readily shedding the water or raised joints (including gutters), should be covered with copper flashing. Sufficient width of copper must be allowed for covering the entire width of the wash and with the back edge of the copper tucked into a joint or groove, properly located according to the particular case, so that there will be no possibility of seepage of water into the structure. This flashing method should be used in every case where the wash pitches inward toward the structure and stops against any superimposed work, such as walls of stories above, parapet balustrading, parapet walls, etc. In no case should gutter grades be formed in archi

FIG. 63.-Modillion cornice with gutter showing method of support and anchorage, construction of gutter, etc.

tectural terra cota. Structural tile, cement, or concrete should be used to form the grade and this in turn covered with metal (see Fig. 63).

On most work the terra cotta contractor, before any manfacturing is done, submits to the architect, for his correction and written approval, carefully prepared shop drawings showing the jointing of all work, anchoring of projecting members, etc., and the engagement of the terra cotta with the masonry or steel work, and any unusual, difficult or special construction that may be required to be clearly shown. A typical example is illustrated (see Fig. 64).

Anchors for securing the terra cotta in place are furnished either by the terra cotta manufacturer or by the contractor for the erection of the work. If it is desired to include the furnishing of these anchors, bolts, etc., as a

part of the contract for setting, the manufacturer will furnish a schedule of the size and number of all anchors, clamps, dowels, hangers, brackets, and special work necessary to securely anchor the terra cotta to the masonry backing and to the structural frame, and to support any projecting pieces. This miscellaneous metal work can frequently be purchased in the local market more economically that it can be furnished by the terra cotta manufacturer. Provided that sufficiently detailed information can be given the bidders to enable them to accurately estimate the quantity of metal required, it is generally recommended that the furnishing of all anchors, ties, etc., be made a part of the contract for the setting of the work.

FIG. 64.-Section through lintel, cornice, and FIG. 65.-Elevations and sections of three simple types of lintels sill in connection with concrete construction.

in brick walls.

The metal used for securing the terra cotta to the frame work should not be less than 14 in. thick and hanger bolts and dowels not less than 11⁄2 in. in diameter, increasing the diameter in proportion to the weight of the pieces. Ashlar anchors should be X 1 in. Wherever practical, all wall and strap anchors should be cut and bent on the scaffold. All metal work should be painted two coats of red lead and oil, and allowed to dry before using. Gal

vanizing makes anchors brittle and fills up the threads of bolts and adjustable anchors, thus necessitating rethreading and causing unnecessary delay.

In terra cotta, as in every other type of building construction, few features are of more importance than the methods of accomplishing tight results over openings in walls. Three illustrations are shown in Fig. 65 of the simplest typical lintel construction. Other types of soffits and lintels over openings, increasing in depth, ornamentation, or size and number of pieces, with each illustration, are shown in Figs. 66, 67 and 68.

170. Setting.-Terra cotta is usually set by the mason contractor. Where, however, the contract is large enough, good results can sometimes be obtained by having the manufacturer do the setting.

All supports for terra cotta including angles, rods anchors, etc. should be designed so as to permit of easy adjustment to the reasonable requirements of construction when the material is being set

4x1" Tie to angle

Double angles supporting cornice, balcony, and similar blocks separated for hangers carrying modillions or brackets below

May be adjusted sidewise under inner continuous channel to desired position

Pipe for carrying brackets and modillions.

Outer end resting in hanger, inner end in masonry

Diagrams of Cornice, Modillion, and Bracket Support

FIG. 69.-Details of iron anchors, hangers, straps, clips, etc. used, in setting architectural terra cotta. The terra cotta for the various portions of the work should be assembled at the building and the sizes checked off, as so to verify the joint allowance and to guard against variations which might have occurred in the frame work or superstructure of the building as thus far erected.