As has been suggested, to implement an open building system and to industrialize the building industry effectively, the size of all building products must be dimensionally coordinated.

SEF recognizes the standard 4" module as defined in CSA A31-1959, as far as it does not impede function. The selection of the module affects both the vertical and horizontal planning grids on which a system can evolve. The alternatives were a two-way horizontal planning grid with an independent vertical planning grid, or a three-dimensional space grid. The two-way horizontal planning grid with an independent vertical planning grid was chosen because it corresponds better to traditional building methods. The horizontal planning grid selected is 5'0" X 5′0′′ (60" X 60") and the vertical planning grid is 12" (1′0′′).

(a) Horizontal Planning Grid: The 5'0" X 5′0′′ horizontal planning grid was selected because:

(1) It fits accurately to the space requirements recommended in the SEF academic research studies, and it satisfies the Metropolitan Toronto School Boards' ceiling cost formula.

(2) Since it is the largest planning grid which fits the basic space requirements, it reduces joints to minimum.

a

(3) The planning grid accepts the 4'0" fluorescent lighting tube in a variety of arrangements with an adequate allowance for partition thicknesses and other obstructions of the ceiling plan surface. Among major manu facturers of lighting-ceiling systems who were consulted, there were requests, on grounds of economy, to specify 4'0" fluorescent tubes rather than 3'0" tubes.

(4) Since the 5′0′′ ×5′0′′ planning grid has been used for the SCSD project in Southern California and the Florida State School Building Program, a number of building materials based on this planning grid have already come into existence.

(5) It is approved by a variety of structural, lighting-ceiling, partition, and vertical skin product and component manufacturers.

(6) Since the subsystems are commonly used in commercial building, the subsystems of the first SEF building system can be directly applied to buildings other than schools.

(7) The large ceiling grids formed on the planning grid provide a relatively tranquil visual environment.

(8) It appears to have dimensional appropriateness and in particular most partitions aline themselves on this planning grid.

(9) It can be divided into a 20-inch subgrid which has been suggested as a suitable grid in the design of residential high-rise buildings. Materials and subsystems designed to fit this residential planning grid could be used in buildings using the 5'0" X 5'0" planning grid. (b) Required Dimensions: Required dimensions refer to the elements of the structure subsystem and are related directly to the planning grid of 5'0" X 5′0′′.

Required dimensions for primary spans: 10'0", 15′0′′, 20'0", 25'0, and 30'0".

Required dimensions for secondary spans: 5′0′′, 10′0′′, 15'0", 20′0′′, 25′0′′, 30′0′′, 35′0′′, 50′0′′, 60′0′′, and 65′0′′.

Spans beyond 65′0′′ advance on a 5'0" increment and will be custom fabricated.

(c) Application of the Dimensional Criteria: Planning: All buildings using the SEF Building System have been laid out on a 5'0" X 5'0" planning grid. The overall dimensions and form of all buildings are governed by this planning grid. Consequently, all structural plan dimensions and alf dimensions of exterior walls are multiples of 5'0"; all changes of direction of wall planes in plan are multiples of 5'0".

Al changes of direction in plan form take place about a column. The structural subsystem performance specifications require braced bays to stabilize SEF framed buildings. The location of these braced bays will be the responsibility of the architect and engineer for each project.

The SEF Building System is not capable of accommodating cantilevers, either of the structure or of canopies, columns supported on primary or secondary beams, or sloping walis or roofs. Should a demand arise for these structural configurations, future versions of the successful building subsystems may include provisions for these configurations.

(d) Building Heights: The SEF Building System is suitable for the construction of buildings up to five stories in height with one floor on grade, four suspended floors and a roof. The full number of stories for the building system has been selected to coincide with the requirements of the National Building Code and represents the point of division between 1- and 2-hour construction.

The First SEF Building System can be used on all forms of building sites and is capable of application to buildings which have varying roof and floor levels within the same buildings. Clear ceiling heights from finished structural floor surface to finished ceiling soffit are as follows:

10'0"-Most tutorial, library, and laboratory spaces. 14'0"-Shops, music rooms, and some large group areas. 18′0′′--General purpose rooms and large group areas. 24'0" Gymnasiums.

Each of the above nominated clear ceiling heights may also be used for a variety of circulation and service spaces. The required dimensions for the floor and roof sandwich thick

nesses are:

Up to 65'0" clear spans-4'0". Over 65'0" clear spans-5'0".

(e) Floor Roof Structure/Service Sandwich: The structure/service sandwich is a grouping of structural, atmospheric, and electrical subsystems integrated with finishing and weatherproofing subsystems, contained between two flush, parallell planes.

This sandwich which may be a “roof sandwich” or a “floor sandwich," includes spatial and depth provision not only for hard elements such as beams, slabs, lighting fixtures, and ducts, but also for "soft elements" such a space allowance for future unpredictable services. The latter may include wires and other cables, and pipes and services for undetermined future functions.

(f) Tolerances: All tolerances to an interface plane are negative. Within this negative interface tolerance, manufacturing tolerances will be positive and negative.

In principle, the first SEF Building System aims for a loose fit approach to component integration to allow for the inaccuracies which are common to the building industry.

1. INTRODUCTION Construction research have been conprograms ducted at Battelle's Columbus Laboratories almost from its inception. The Construction Systems, Planning, and Economics Research Division, which has responsibilities in some of these areas, consists of engineers, architects, market analyses, and economists. We are currently involved with new construction methods and techniques: Development of design criteria; development of performance specifications for new products and components; evaluation and development of industrialized building systems; and conduct of conceptual architectural, financial, and planning research. It is an honor to have the opportunity to relate our work to that of the A62 Committee in delivering this paper on the current status of dimensional precoordination in the United States.

2. CURRENT STATUS OF DIMENSIONAL

PRECOORDINATION

Historically, aesthetic proportions and traditional building methods have been the main generators of dimension coordination. Aesthetic dimensions were highly developed into a series of coordinated proportions by the Greeks and Romans and were again popularized during the Renaissance. The building process has been an important generator of modular coordination as has the optimal size and weight of a component. For example, the proportion of bricks is based upon the shape, weight, and dimensions that are most easily grasped and laid by a mason.

The concept of dimensional coordination of manufactured components in the construction industry is directly tied to the 19th century industrial revolution. The traditional stick method of cutting and fitting each part of a building as a custom craft activity has only been replaced by the rationalized method of building using components and products that are premanufactured and then brought to the site for assembling. One of the earliest examples of industrialdimensional coordination and interchangeability was the gages for ammunition and guns developed in 1776

by French Lieutenant General Gribeauval. Similar developments in the United States were pioneered by Eli Whitney in 1800 when he produced rifles on the first assembly-line basis. English innovator of dimensional coordination, Joseph Whitworth, commented in 1856 on the effect of standardization in building components:

Suppose for instance, that the principal windows and doors of our houses were made only of three or four different sizes. Then we should have a manufactory startup for making doors, without reference to any particular house or builder. They would be kept in stock and made with the best machinery and contrivances for that particular branch; consequently, we should have better doors and windows at the least possible

cost.

Although modular coordination was introduced in the 1920's, it was not until the thirties that Albert Bemis outlined the idea of a full-dimensional coordination for the building industry based upon the use of components, the dimensions of which were multiples of a 4-inch module. The first standard for modular coordination was adopted in 1945 and the A62 Guide on Modular Coordination that first established 4 inches as the basic module was published in 1946 by the Modular Service Association. Since then, work was undertaken by the Modular Building Standards Association (MBSA) and more recently by the American National Standards Institute (ANSI) under the sponsorship of the National Bureau of Standards.

Currently the supply complex of the construction industry operates as a modified open system. In general, each building component or product is related by standards or tradition into functional groupings. Functional coordination by product type is well ilustrated by Sweets Catalogue or Graphic Standards. Coordination of dimensional standards and often performance criteria has been developed within most functional groupings by tradition, individual manufacturers, trade associations, institutes, or government agencies. The membership list of the A62 Committee is composed of over 55 such groups or individuals. Although the A62 Committee has just recently published basic module of 4 inches for horizontal dimen

sioning, dimensional coordination has been inherent within the construction industry.

Most products, however, are designed to be used in the custom building market where they are field adapted. Architectural and Engineering News recently estimated that cutting and fitting now takes from 5 to 45 percent of construction time. Many products are not universally used or interchanged from one project to another due to lack of coordination in joint design and/or standardize dimensions. Often components are part of a closed system due to the proprietary nature of the building industry and its supply complex. Curtain wall systems and metal building have much duplication, but little interchangeability. Within a closed system, interchangeability is not critical as all components and joints are designed to interface. In open systems, components coordination between different functional groups will allow for the installation of preassembled subsystems even if various manufacturers produce them. Interchangeable components could be removed, relocated, or replaced without destruction of the assembly itself or to other elements of the buiding.

When considering dimensional coordination, one must differentiate between different types of interface connection. J. F. Eden in England has referred to these differences as the "degree of restraint." In lap joints, stacking, or surface mounting, there is little restraint as long as the overall height or length is not critical. However, once assemblies have to fit together where their edges interface, dimensional coordination becomes critical.

The choice of a 4-inch module as the basis for the horizontal dimensioning of coordinated building components and systems conform to most current dimen

sional systems used in the construction industry. The system module selected in the U.S.A. Standard A625 was 60 M or 20 feet. Into this module, the factors of 2, 3, 4, 5, 6, 10, 12, 15, and 20 provide for component coordination. I shall now briefly review these factors and list how they conform to the dimensional system inherent in conventional building.

M (4") 1⁄2 M (2")

M, 2 M, 4 M (4, 8, 16′′)

3 M (12")

4 M (16")

5 M (20") 6 M (24")

10 M (40")

12 M (48")

15 M (60")

60 M (20 ft)

Basis for nominal dimensions of graded lumber, steel, and precast masonry.

Standard masonry nominal dimensions for brick, block, and related products.

Common increment of framing and component materials. Accepted spacing for stud wall construction.

12 metric module.

Standard width of precast masonry components (deck) and accepted stud spacing in selected materials. Nominal equivalent to the metric module, but has not been widely used in the United States. Most common component module for sheet materials, and also used in interior partition and integrated ceilings as planning module. Widely used as the basic planning module in integrated ceilings, office layout, and flexible partitions. Large enough for a systems module, yet flexible enough for multiple use. It has not been as widely used as the 12-ft. module which is generally used for mobile homes and sectionalized buildings. Currently most proprietary frame and box building systems do not conform to a specific set of dimensions.