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Reinforce all thin walls, particularly at their junction with other work—and amply, as they are easily thrown into tension. Do not put in an absurdly small quantity of steel in a large structure, as it has no motive.
"A great deal of money can be saved in the design by using leaner mixtures in foundation and mass work than is common practice. It is not uncommon to see a 1:2:5 mixture which would safely carry a load of 20 tons used in a large foundation where the supporting clay will only carry a couple of tons per sq. ft. Of course, in using lean mixtures, it requires better mixing and better supervision.
"Where first-class foundation soil cannot be econom ically reached, use reinforcement in the foundations to spread your load over the area, and use a reinforced superstructure in order to lighten the loads on your foundation.
"Aesthetic Appearance. The monotonous uniformity of color in concrete work can be varied by using sands or crushed stones of different color, and by using dif ferent kinds of tools in dressing the work. This method of varying the color is preferable to using artificial color ing matter, which, as a rule, bleaches out and weakens the cement.
"It is extremely difficult to build long reaches of plain walls quite plumb ; and therefore, even assuming that you are going to have first-class inspection on your work, it is well in the design to hide this class of defects by breaking up the plain surface by pilasters having projections from three inches to several feet. Belt courses should be used as often as consistent with appearances for a similar reason.
"Don't use a very ornamental balustrade of concrete. If it is forced upon you, I would suggest turning it over to one of the imitation stone companies who execute this special class of work. Remember that the balustrade or parapet receives constant close inspection by the public, who are accustomed to fine marble and granite details and are looking for it in concrete work, which is often made to simulate these materials.
"Don't under any circumstances select marble details for concrete work. They are too fine. Select concrete details, and you will get a better-looking piece of work.
If you want the best work which can be executed with concrete, trim your structure with stone block, or, if this is too expensive, with concrete blocks, cast sepa rately, and afterwards dressed and set in place. In this way you are sure of your trimming (particularly your corners). Concrete is an excellent filler, not unlike rub ble and brick; and in the best designs I think it should be used as a filler. There is no trouble getting good vertical plain faces by spadding or building up the mortar face with the work ; but the corners and fine details give a lot of trouble.
"Don't try to imitate stone work. Confess that your structure is of concrete, and design accordingly. Re member that concrete is a new material with new virtues and vices. Forms are permissible with this material that where impossible for the Greeks and Romans, and the olders forms may not be possible in concrete. If the engineering conditions warrant a lintel 75 ft. long, don't make it look like an arch. It is not necessary. Don't dwarf your structure with excessive paneling, which suggests parlor furniture.
"Don't cut up the arch-rings into voussoirs by nailing strips on the lagging to make it appear that the arch is built of ashlar, unless you are going to lay up the work in alternate transverse blocks, in which case it may be desirable. Don't make concrete imitate something that it is not.
"Don't put a lot of gingerbread on a simple structure just because you can get it almost as cheap. Efflorescence does not mar simple details nearly as much as it does ornate ones.
"Face Work. Remember, in block work used for trimming mass concrete (that is, work cast on the ground and set in place), that it is not, as a rule, cheaper to use thin veneers with 6-in. and 8-in. beds. Use a bed at least equal to the rise. It does not cost any more money; and when you back it up with concrete, it will stand the pressure of the wet concrete; and if you have sufficient bed, the blocks will be useful in fastening the forms of the mass work. Use hollow spaces or gouge spaces in the back of trimming blocks, to bond the blocks with the mass concrete.