or the water can be applied with a hose. When a hose is used, the best way is to spray the water. This can be easily accomplished by compressing the end of the hose. Care must be taken to apply the plaster at once, and before the wall has had an opportunity to dry.

If the plaster is applied to a dry, porous surface, the latter will take up so much water that the cement in the plaster will not set. This causes the plaster to dry out, crack, and fall off, and is usually

the cause of most of the unsatisfactory results in the use of cement plaster.

Application of Stucco to Brick.-The treatment of a brick surface is very similar to that of a stone exterior. The porous nature of the brick, however, necessitates the utmost care in wetting before the first coat is applied, or the results will not be satisfactory. If the brick wall has been painted and this paint is scaling off, as it so often does, it should be thoroughly scraped and cleaned, and all loose mortar removed. If possible, the old mortar should be picked out 1/2 to 3/4 of an inch from the face of the brick-work, and when the first coat is applied it is forced into these crevices and forms an excellent bond. The comparatively smooth surface of the brick

wall will require less material for the first coat than a rough surface of stone. The first coat over the brick-work must be scratched thoroughly and allowed to set until it is strong enough to support the second coat. The second coat is then applied in the same way as has been described.

The original smooth surface of the brick wall lends itself very readily to a smooth plaster finish. This is obtained by using a

FIG. 29.-Hollow Concrete Tile and Stucco Wall and Floor Construction.

finish coat containing rather fine sand and placed with a steel trowel. When it is desired to obtain an Old English style of exterior, the smooth finish coat is necessary. Very artistic and desirable results have been secured by thus renovating brick exteriors.

Stucco on Hollow Tile.-Walls of hollow tile form an ideal framework for stucco houses, on account of their strength, indestructibility by fire and insulation against heat and cold. When properly surfaced, such blocks also furnish an excellent bond to the stucco, so that plastering can be applied directly to the tile without furring or lathing. This bond is obtained by indenting or scoring the surface of the tiles by a series of corrugations, by leaving the surfaces rough, and by the use of dovetailed grooves to receive cement, plaster, and stucco. The tile should in all cases

be well wetted before applying the mortar, and if the weather is hot, it will be necessary to spray the finished wall twice a day for a period of three or four days after the completion of the work.

Application of Stucco to Concrete.-The treatment of a concrete surface that needs to be plastered depends upon whether the wall is new or old. The best results are obtained by placing the plaster immediately after the forms have been removed and while the concrete is still green. In this case very little or no preparation of the concrete is necessary to receive the plaster, which is applied

FIG. 30.-Artistic Garage. Stucco on Pipe Frame.

before the wall has dried out. A single coat is usually all that is required, and the finish desired may be secured in the same manner as with the final coat over a stone or brick exterior. If the concrete wall is old, much care must be taken in preparing it for the plaster. The excess of cement likely to have flushed to the surface must be removed and the surface thoroughly cleaned and well wet before applying the plaster, or it will crack and fall off. By the use of facing forms, new walls may be constructed in which the piaster finish and concrete wall are carried up simultaneously, resulting in a perfect bond between the two.

Renovating Frame Buildings.-Old frame buildings can be readily renovated by the use of cement stucco. The exterior is covered with lath furred out as already described and either two or three coats are applied. In such a case it is necessary to bring out the door and window trim unless the plaster is to finish flush with the old trim, or if it is desired to keep the old frames and have them project, it will be necessary to remove the old siding and staple the furring directly to the old studding. Frequently the trim is removed and the lath brought around the casing, thus getting a recessed window with no wood showing.

Quantities of Materials for Stucco.-The quantities of cement and sand required for stucco work vary with the thickness of the coat and the proportions of the ingredients. The following table shows the covering power of a barrel of cement when made into mortar for thicknesses varying from 1/2 to 1 inch, and for proportions varying from II to I: 3 mixtures of cement and sand.

TABLE IX.-AREA COVERED BY MORTAR.

Produced from One Barrel of Portland Cement Mortar (3.8 cu. ft. Cement Paste). No Lime.

CHAPTER XII

THE ARTISTIC TREATMENT OF CONCRETE

SURFACES

Imperfections in Concrete Surfaces.-Methods of Finishing Surfaces.-Spading.— Stucco.-Mortar Facing.-Grouting.-Scrubbing and Washing.-Etching.— Tooling. Selected Aggregates.-Tinting and Coloring.-Panelling, Mosaics, Carving, etc.-Prevention of Cracking and Crazing.

CONCRETE is a plastic material which can be moulded and modelled at will, and as such the temptation is strong to cast it into forms strongly suggestive of some other material. "Beauty, however, in structural design is worthy the name only when, like beauty in Nature, it has character. It must not be a servile copy of the style peculiar to some other material, but in fact must express its own individuality without dissimulation.”*

Imperfections in Concrete Surfaces. Good design requires that the surface must be finished so as to produce a pleasing effect. In many concrete structures the surface is irregular, uneven in texture, and stained or discolored or of lifeless hue. Imperfections in the surface of concrete are due to one or more of the following causes: 1. Imperfectly made forms.

2. Carelessly mixed or placed concrete.

3. Use of forms with dirt or cement adhering to the boards.

4. Efflorescence and discoloration of the surface.

5. Shrinkage cracks, and crazing of surface.

In well mixed and placed concrete, the film of cement paste which flushes to the surface will take the impress of every flaw in the surface of the forms. It will even show the grain marks in welldressed lumber.

Joint marks may be eliminated wholly or in part by pointing the joints with clay or mortar or by pasting strips of paper or cloth over them. Grain marks and surface imperfections can be reduced by oiling the lumber so as to fill the pores or by first oiling and then filling the coat of oil with fine sand blown against the boards. *A. O. Elzner on "The Artistic Treatment of Concrete."