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range of projects utilizing architectural precastconcrete. During the conceptual stage the designermust consider the cost implications of material selections,textures, surface geometries, cross-sections, piecesizes, unit repetition, and erection methods. The variationsin scope, complexity, and detailing make it difficultto provide accurate cost information for a projectin terms of price per square foot (m2) of wall area priorto completion of the design concept.After a design has advanced to the schematic stage,and the general shapes, colors, and finishes havebeen defined, more accurate cost estimates can beprovided. Until this stage is reached, architects areencouraged to seek the advice of precasters andconsultants. Selected guidelines regarding cost ofarchitectural precast concrete are included in this chapterfor further assistance.The architect who desires a more detailed understandingof the cost factors involved in precast concreteconstruction is advised to study both SurfaceAesthetics in Chapter 3 and Design in Chapter 4.Many of the recommendations in these chapters are, inthe final analysis, based upon considerations of economy.Chapter 6, dealing with Guide Specifications,

will highlight the items that should be included in thespecifications in order to define the optimum qualityfor a specific project. This in turn shouldhelp in obtaining accurate proposals frompotential bidders.The nature of precast concrete is suchthat nearly anything that can be drawn,structurally designed, and readily transportedcan be constructed. To do thiswithin reasonable and stated cost limitsrequires careful consideration of designand detailing. Several cost factors influencingarchitectural precast concrete are

interdependent on each other. For example, a cost-efficientsculptured or intricate design may be achievedwithin a limited budget by selecting economical concretemixtures and finishes combined with repetitiveunits and efficient production and erection details.The small college library shown in Fig. 2.1.1 is clad inexposed aggregate architectural precast concrete. Thesmooth horizontal banding and window trim detailingcontrasts with the rough texture of the exposed aggregatefacing. The effect achieved is similar to that ofthe molded stone banding contrasting with the roughcut stone on many of the surrounding older campusbuildings. Use of repetition made the precast concrete

panels more cost effective than cut stone.Repetition in panel design is also the key to achievingquality and economy in the design of walls. During thedesign stage, the exterior walls of a typical office buildingcan be analyzed at three basic locations:(1) At lower level floors, normally the ground floorand mezzanine are where significant architecturalexpression and detailing will occur;(2) At all typical floors where repetition of panel size,shape, and finish occur; and

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(3) At the top floor, parapet, mechanical floors,and penthouse, where there is a likelihood ofincreased panel lengt