CONSTRUCTION NOTES 327 



the base in order to leave the large aggregate protruding to form as an 

 anchorage for the Kentucky rock asphalt. On top of this spread two inches 

 of Kentucky rock asphalt cold. This should be straight-edged and rolled 

 with a hand roller to an even finish. Broom over this a light coating of 

 white Portland cement and allow to set two weeks before using. Lines can 

 then be painted on this court with street marking white paint, which is 

 practically the only maintenance required for the remainder of the season. 



Concrete courts. Most of the statements in favor of asphalt courts 

 apply equally to concrete surfaces, and park and recreation departments in 

 many cities have installed concrete courts. In 1916 the Board of Park 

 Commissioners of Minneapolis constructed sixty-five tennis courts of various 

 types, only two of which were concrete. The concrete courts proved so 

 satisfactory that twenty-four new concrete courts were constructed by the 

 board in 1925. The average cost of these courts was $1,240.38 per court, 

 including enclosures, net posts, and drainage an unusually low price. 1 



Specifications for Minneapolis courts. The following is a summary of 

 the specifications for two or more concrete courts constructed in 1925 by 

 the Board of Park Commissioners in Minneapolis: 



The subgrade to be stripped of lawn and excavated to nine and one-half 

 inches below finished surface of court if clay, or four and one-half inches 

 if sand, gravel or readily drained material. Subgrade to be compacted uni- 

 formly, fill within nine and one-half inches to be made of steam boiler 

 cinders or gravel, not exceeding four inches; this to be spread in layers not 

 to exceed six inches in thickness and compacted. Tile drains to be installed 

 in ditches back-filled with pebbles or stone not smaller than one-half inch. 

 Sub-base to be of steam boiler cinders or gravel kept thoroughly wet, to 

 be spread and rolled thoroughly to a surface at least four and one-fourth 

 inches below finished grade. Grade of each finished court to be two plane 

 surfaces, intersecting at net line and with pitch of three inches from rear 

 edge to valley at net line, the valley to be constructed separately, itself 

 monolithic for each court, and to have pitch of three inches from side of 

 court adjoining second court to outside edge of court. Highest point of 

 valley to be one-fourth inch below edge of adjoining plane surface, expan- 

 sion joints to be provided. Surface of court to be at its lowest outside 

 point three inches above natural level of adjoining ground, which shall be 

 shaped up to court. 



Construction. Thickness of concrete to be not less than four and one- 

 fourth inches. Strips of prepared felt four and one-fourth inches wide and 

 one-half inch thick to be placed to form a joint at net line on each side of 

 valley. Construction joints to be formed by placing the concrete of slabs 

 directly against slabs that have hardened. Concrete base to be mixed in 

 proportion by volume of one sack of cement to two and one-half cubic feet 

 fine aggregate and four cubic feet coarse aggregate of graded crushed rock 



'The Portland Cement Association, with headquarters at in West Washington Street, Chicago, Illinois, 

 but with branch offices in many of the larger cities, has issued an illustrated booklet entitled "Tennis Courts 

 for All-Year Sports," containing much information and detailed directions for constructing concrete courts. 



