Since 1962, architect Pa u lRudolph of New Ha ven, Co n-

necticut, has been developing atechnique for building in concre t ewhich demonstrates a new meansfor achieving a beautiful concre t efinish. In the Yale Un i versity Art andA rc h i t e c t u re building in Ne wHa ven, and in the Endo Labora t o-ries building at Ga rden City, LongIsland, Mr. Rudolph has built witha rough concrete surf a c e. Ra t h e rthan showing the wood texture ofthe concrete forms after they havebeen re m oved, this surface show sthe beauty of the concrete itself.

M r. Ru d o l p h’s method invo l ve sthe pre p a ration of finned form s. Ona plywood backing, tra p ezoidal fins2 inches deep by 1 _ inches at thebase by _ inch at the top are nailedin place. They form a regular pat-t e rn, the space between the fins be-ing equal to the width of the fins.

These forms are placed as usualfor any concrete wall. A stiff mixtureof concrete with about a 2-inchslump and 1- to 1 1/2-inch aggre-gate is then placed. Cement, sand,and aggregate for the entire job arestock-piled before starting in ord e rto assure consistency of surf a c et o n e. After re m oval of the form s, thefins are broken off with a hammer,thus exposing the aggre g a t e.

Often the aggregate breaks alongwith the concre t e, and the interi o rtones of the aggregate are exposed.The stiff mixture avoids filming ove ra g g regate stones which are not bro-ken. In this way, the building takeson the warm tone of the aggre g a t e.

This method does more than dec-o rate an otherwise smooth concre t es u rf a c e. Often used both inside and

o u t s i d e, it eliminates the necessityof any further finishing of the con-c re t e. In addition, the ve rtical finss u p p ress the subtle color changesvisible in a smooth concrete surf a c e.

The finned method of concre t es u rface treatment was deve l o p e dfor the building at Ya l e, where Mr.Rudolph is chairman of the arc h i-t e c t u ral department. Se ve ral experi-ments we re made before the suc-cessful method was found. On ee x p e riment invo l ved backing thet ra p ezoidal elements with cro s ss l a t s, in order to achieve the ro u g hs u rface without the necessity ofh a m m e ring. This method, howe ve r,was found to produce too weak af o rm when applied to the scale nec-e s s a ry in building. There f o re, theplywood backing was used. A larg esample section was placed on thebuilding site before the method wasa p p rove d .

Nearly all concrete surfaces in theYale building are treated with therough finned technique. The fourh o l l ow rectangular pillars which arethe major stru c t u ral elements ri s i n ginside the building are finished inthis way. Those walls which are notglass are also treated with fins. On l yp a rts of the basements and the sixthand seventh floors, where art i s t sneed tackable surf a c e s, are given asmooth finish.

The Long Island labora t o ry differsf rom the Yale Art and Arc h i t e c t u rebuilding in two ways. First, thefinned technique, used only on flats u rfaces in New Ha ven, is applied toc u rved surf a c e s. In most places thisis done without the necessity ofc u rving the form s. The tra n s i t i o n sb e t ween 1-foot flat segments set on

a curve are easily obscured by theactivity of the fluted surf a c e. The ap-p e a rance is that of a true curve. At rue curve was, in fact, used on thef o rms of only a small portion of theb u i l d i n g .

On the whole, the cord u roy sur-face is used more sparingly at En d o.The only interiors finished with therough surface are those of the tur-rets on the office wing and of thel o b by. The remainder of the build-ing called for smooth interior finish,since it is to be used for labora t o ri e s.

Ge n e ral contractor for Ya l e’s Artand Arc h i t e c t u re building was theGe o rge B. H. Macomber Co m p a n y.The aggregate for the Yale buildingwas brought from Easton, Ma s s a-c h u s e t t s. The Easton stone was cho-sen for its warm ye l l ow and goldtones which would be exposed bythe hammeri n g .

The aggregate for the Endo build-ing was a standard bank-run gra ve lf rom Long Island. This stone has ahigh percentage of light-colore dq u a rtz. All the concrete work on thatbuilding was done by the Ce n t ra lCement Finishing Company of Ne wYo rk City. Ge n e ral contractors we reWalter Kidde Co n s t ru c t o r s.

Both jobs ran an ave rage cost of$26.00 per square foot. The Ru d o l p ht reatment calls for one to two dol-lars more per square foot than ac o n ventional concrete surf a c e. Thisf i g u re includes the extra one inch ofwidth which must be allowed in thevolume of concre t e, and the cost ofc reating the fluted form s. The flutedt e c h n i q u e, howe ve r, still under-p rices many altern a t i ve surf a c et re a t m e n t s, since the final surface isbuilt into the concrete walls.

Paul Rudolph’sFluted Concrete Buildings

A chipper, one of four employed nearlyfull time on this aspect of theconstruction of the Yale building,executes the final step in creating thecrusted concrete surface. Forms havejust been removed from flutings at theleft. Note that practically no pebbles arevisible in the concrete. Photo shows achipper breaking off the fluting with ahammer, exposing the aggregate. Onepiece of broken concrete flies off (infront of shadow).

A stack of the concreteforms (left) used toachieve the fluted,crusted surface of Yale’sArt and Architecturebuilding. These flutedforms were cut and madein a shop on the buildingsite.

Endo Laboratories, Garden City, Long Island. Nearly allsurfaces of this building are finished in the same crustedtechnique.

The Art and Architecture Building at YaleUniversity was designed by architect Paul Rudolphand is built chiefly of reinforced concrete. Theunusual fluted concrete finish is used on bothinterior and exterior surfaces.

Sketch shows details of construction of forms for casting of thewalls. Beveled fir strips were nailed on vertically and secured withwalers and 1/2-inch bolts.

PUBLICATION #C650084, Co py right © 1965, The Ab e rdeen Gro u p, All rights re s e rve d