Motion Picture Herald (Sep-Oct 1943)

BETTER THEATRES October 16, 1943 Floors for Stadium Plan on Sloping Ground 72 the system of floor pitches submitted in this article is for another stadium plan. In the September 18th issue we came to the stadium type of auditorium, offering a scheme for the auditorium plan which was designated Type 2C in the March 6th issue. This time we go back to Type 2A, having gone ahead to Type 2C in the previous article because the floor slope involved in it was similar to the one which was being discussed in that article with respect to a single-floor plan. Auditorium Type 2A was described in the March 6th issue as an auditorium with a stadium, built on ground sloping 2 feet or more downward toward the screen end and having a total seating depth, including the stadium, up to 30 rows. The accompanying longitudinal section shows how the considerations of floor slope, projection angle, volume and sign are inter-related. In dealing with single floor theatres we have seen how the contour of the natural By BEN SCHLANGER ground influences the selection of the design of the slope, suggesting more or less of a reverse floor near the screen, and decreasing the amount of the regular downward slope toward the screen as necessary to conform as nearly as possible to the contour of the natural ground and to offset the effect of increased seating depth. A point was always made of trying to keep the sill of the exit doors near the screen slightly above rather than below the level of the natural ground at the screen end. It is much easier to arrange a ramp, or steps, to go down from the exit door sills to the natural ground than it is to ramp up or step up from exit door sills to a higher natural ground line. The latter condition causes water pockets at the ramps and excess excavation whereas the former condition requires only ramps or steps down as may best suit the particular condition. Now with the introduction of upper levels of seating we shall find that there are other important considerations in determining the type of floor slope to be used. It will be observed that greater amounts of reverse floor design becomes necessary when various types of upper level seating are introduced. It will be found practical and advantageous to accept a condition whereby the level of the first row of seats on the main floor is higher than the natural ground at that point. Accordingly, in upper level seating schemes various degrees of reverse floor slopes will be used to achieve the following: 1. Reduce the height of the risers of the stepped platforms, using 8 inches as a maximum riser, thereby eliminating the need for hazardous intermediate steps between seating platforms. 2. To keep level B shown in the accompanying drawing low enough to control the downward viewing angles (this point was discussed in an article in the issue of November 14, 1942). 3. To keep this level B low enough to permit placing the projection so as to require a small projection angle. 4. To keep the projection room low so as to make it possible to place the main auditorium ceiling low, thus to control the cubage of the auditorium for reasons of acoustical design. Now, to refer to the accompanying drawing, level B is controlled by level A, and also by the distance from the screen to the first row of the upper level of seating. As this latter distance decreases, level B is forced upward ; at the same time, the small{Continued on page 79) PROJECTION RM ; POSITION A 22 21 LINE OF NATURAL SLOPE OF THE GROUND ROW l£V£LS ROW NUMBERS FLOOR PITCHES FOR STADIUM TYPE AUDITORIUM ON SLOPING GROUND (see text) Scheme for Type 2C auditorium, on ground sloping 2 feet or more downward toward screen end and having a total seating depth up to 30 rows (22 rows on main floor, 8 rows in stadium). The main floor slope is an adaptation of one previously presented as Slope No. 3. The levels given for the main floor are the same as given for the 22 rows of Floor Slope No. 3. All levels are given as a plus dimension above the datum line, which is the lowest point of the main floor. All pitches and rises are noted in inches and in decimal parts of an inch (up to one-hundredth of an inch). For practical construction purposes, five-hundredths of an inch would be sufficiently accurate. In forming the floor for the main level, an accurate template taking in three rows at one time should be used to run the finished cement work.