Engineering and Construction

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Once the schematic design is approved by the owner, the process of designing the building in greater detail begins. During this stage, the schematic design is developed further—hence the term   design development  (DD) stage.

While the emphasis in the SD stage is on the creative, conceptual, and innovative aspects of design, the DD stage focuses on developing practical and pragmatic solutions for the  exterior envelope, structure, fenestration, interior systems, MEPF systems, and so forth.

This development involves strategic consultations with all members of the design team. Therefore, the most critical feature of the DD stage is decision making, which may range  from broad design aspects to details. At this stage, the vast majority of decisions about  products, materials, and equipment are made. Efficient execution of the construction documents depends directly on how well the DD is managed. A more detailed version of the specifications and probable cost of the project is also prepared at this stage.  

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The schematic design gives graphic shape to the project program. It is an overall design concept that illustrates the key ideas of the design solution. The major player in this stage is the architect, who develops the design scheme (or several design options) with only limited help from the consultants. Because most projects have strict budgetary limitations, a rough estimate of the project’s probable cost is generally produced at this stage.

The schematic design usually goes through several revisions, because the first design scheme prepared by the architect will rarely be approved by the owner. The architect communicates the design proposal(s) to the owner through various types of drawings—plans, elevations, sections, freehand sketches, and three dimensional graphics (isometrics, axonometrics, and perspectives). For some projects, a three-dimensional scale model of the entire  building or the complex of buildings, showing the context (neighboring buildings) within which the project is sited, may be needed.

With significant developments in electronic media technology, especially building information modeling (BIM), computer-generated imagery has become common in architecture and related engineering disciplines. Computer-generated walk-through and flyover simulations are becoming increasingly popular ways of communicating the architect’s  design intent to the owner and the related organizations at the SD stage.

It is important to note that the schematic design drawings, images, models, and simulations, regardless of how well they are produced, are not adequate to construct the building. Their objective is merely to communicate the design scheme to the owner (and to consultants, who may or may not be on board at this stage), not to the contractor.

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The    design phase   begins after the selection of the architect. Because the architect (usually a firm) may have limited capabilities for handling the broad range of building-design activities, several different, more specialized consultants are usually required, depending on the size and scope of the project.

In most projects, the design team consists of the architect, civil and structural consultants, and mechanical, electrical, plumbing, and fire-protection (MEPF) consultants. In complex projects, the design team may also include an acoustical consultant, roofing and waterproofing consultant, cost consultant, building code consultant, signage consultant, interior designer, landscape architect, and so on.

Some design firms have an entire design team (architects and specialized consultants) on staff, in which case the owner will contract with a single firm. Generally, however, the design team comprises several different design firms. In such cases, the owner typically contracts the architect, who in turn contracts the remaining design team members,  Figure 1.1. Thus, the architect functions as the prime design professional and, to a limited degree, as the owner’s representative. The architect is liable to the owner for his or her own work and that of the consultants. For that reason, most architects ensure that their consultants carry adequate liability insurance.

FIGURE 1.1 Members of a typical design team, and their interrelationships with each other and the owner in a traditional contractual setup. A line in this illustration indicates a contractual rela- tionship between parties. (“MEPF consultants” is an acronym for mechanical, electrical, plumbing and fire consultants.)

In some projects, the owner may contract some consultants directly, particularly a civil consultant (for a survey of the site, site grading, slope stabilization, and site drainage), a geotechnical consultant (for investigation of the soil properties), and a landscape architect (for landscape and site design),  Figure 1.2   . These consultants may be engaged before or at the same time as the architect.  

FIGURE 1.2 Members of a typical design team, and their interrelationships with each other and the owner in a project where some consultants are contracted directly by the owner. A solid line in this illustration indicates a contractual   relationship between parties. A dashed line indicates a communication link, not a contract.

Even when a consultant is contracted directly by the owner, the architect retains some liability for the consultant’s work. This liability occurs because the architect, being the prime design professional, coordinates the entire design effort, and the consultants’ work is influenced a great deal by the architectural decisions. Therefore, the working relationship between the architect and an owner-contracted consultant remains essentially the same as if  the consultant were chosen by the architect.

In some cases, an engineer or another professional may coordinate the design process.

This  generally occurs when a building is a minor component of a large-scale project. For example, in a  highly  technical project such as a power plant, an electrical engineer may be  the prime design professional.

In most building projects, the design phase consists of three stages:

  •     Schematic  design   stage
  •     Design  development   stage
  •     Construction  documents   stage

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It is a good idea to begin the design of the foundations of a building at  the same time as architectural design  work commences. Subsurface conditions beneath a site can strongly influence fundamental decisions about  a building—its location on the site,  its size and shape, its weight, and  the required degree of flexibility of  its construction. On a large building project, at least three designers  are involved in these decisions: the  architect, who has primary responsibility for the location and form of  the building; the structural engineer,  who has primary responsibility for its  physical integrity; and the foundation  engineer, who must decide, on the basis of site exploration and laboratory reports, how best to support it  in the earth. More often than not,  it is possible for the foundation engineer to design foundations for a  building design dictated entirely by  the architect. In some cases, however, the cost of the foundations may  consume a much larger share of the  construction budget than the architect has anticipated, unless certain compromises can be reached on the  form and location of the building. It  is safer and more productive for the  architect to work with the foundation  engineer from the outset, seeking al- ternative site locations and building configurations that will result in the fewest foundation problems and the  lowest foundation cost.

In designing a foundation, a  number of different design thresh-olds need to be kept in mind. If the  designer crosses any of these thresholds, foundation costs take a sudden  jump. Some of these thresholds are:

•  Building below the water table. If the substructure and foundations of a building are above the water table, minimal effort will be required to keep the excavation dry during construction. If the water table is penetrated, even by an inch, expensive steps will have to be taken to dewater the site, strengthen the slope support system, waterproof the foundation, and either strengthen the basement floor slab against hydrostatic uplift pressure or provide for adequate drainage to relieve this pressure. For an extra inch or foot of depth, the expense would probably not be justified; for another story or two of useful building space, it might be.

•  Building close to an existing structure. If the excavation can be kept well away from adjacent structures, the foundations of these structures can remain undisturbed and no effort and expense are required to protect them. When digging close to an existing structure, and especially when digging deeper than its foundations, the structure will have to be temporarily braced and may require permanent underpinning with new foundations. Furthermore, an excavation at a distance from an existing structure may not require sheeting, while one immediately adjacent al-most certainly will.

•  Increasing the column or wall load from a building beyond what can be supported  by a shallow foundation. Shallow foundations are far less expensive than piles or caissons under most conditions. If the building grows too tall, however, a shallow foundation may no longer be able to carry the load, and a threshold must be crossed into the realm of deep foundations. If this has happened for the sake of an extra story or two of height, the designer should consider reducing the height by broadening the building. If individual column loadings are too high for shallow foundations, perhaps they can be reduced by increasing the number of columns in the building and decreasing their spacing.

For buildings at the scale of one-and two-family dwellings, foundation design is usually much simpler than for large buildings because foundation loadings are low. The uncertainties in foundation design can be reduced with reasonable economy by adopting a large factor of safety in calculating the bearing capacity of the soil.

Unless the designer has reason to suspect poor soil conditions, the footings are usually designed using rule-of-thumb allowable soil stresses and standardized footing dimensions. The designer then examines the actual soil when the excavations have been made. If it is not of the quality that was expected, the footings can be hastily redesigned  using a revised estimate of soil-bearing  capacity before construction continues. If unexpected groundwater is encountered, better drainage may have to be provided around the foundation or  the depth of the basement decreased.

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Certain themes are woven throughout this blog and surface again and again in different, often widely varying contexts. These represent a set of concerns that fall into two broad categories: building performance
and building construction. 

The performance concerns relate to the inescapable problems that must be confronted in every building: fire; building movement of every kind, including foundation settlement, structural defl ections, and expansion and contraction due to changes in temperature and humidity; the fl ow of heat and air through building assemblies; water vapor migration and condensation; water leakage; acoustical per-formance; aging and deterioration of materials; cleanliness; building maintenance; and others.

The construction concerns are associated with the practical problems of getting a building built safely, on time, within budget, and to the required standard of quality: division of work between the shop and the building site; optimum use of the various building trades; sequencing of construction operations for maximum productivity; convenient and safe worker access to construction operations; dealing with inclement weather; making building components fit together; and quality assurance in construction materials and components through grading, testing, and inspection.

To the novice, these matters may seem of minor consequence when compared to the larger and often more interesting themes of building form and function. To the experienced building professional, who has seen buildings fail both aesthetically and physically for want of attention to one or more of these concerns, they are issues that must be resolved as a matter of course before the work of a building project can be allowed to proceed.

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Improving Collaboration Among Team Members
The design and construction industry continues to evolve, testing innovative organizational structures and project delivery methods in which designers, builders, and owners assume less adversarial and less compartmentalized roles. Such approaches share characteristics such as:

•  Contractual relationships and working arrangements that foster collaboration between project members
•  Participation of the construction contractor during the design phases of a project
•  Overlapping of design and con-struction activities to reduce the “time to market”
• Expanded definitions of project services to encompass the full life cycle of a project—from its original conception, through planning, design and construction, to postconstruction occupancy—to better serve the
needs of the building owner

The growth of design/build in the construction marketplace is one example of this trend: Between 1980
and 2005 the share of private, nonresidential construction work per-formed as design/build construction increased from roughly 5 percent of the total market to an estimated 30 to 40 percent. Alternatives to traditional design/bid/build project delivery have gained increased acceptance in the public construction sector as well. Other new practice models, with such names as teaming, concurrent design, integrated practice, or alliancing, combine efficient project delivery methods with innovations in team member relationships in a variety of ways, with the aim of aligning all parties’ efforts with the shared goal of a finished product of  the highest possible quality and value to the owner.

Improving Effi ciency in Production
Other efforts within the construction industry focus on improvements in the efficiency of construction methods themselves. Unlike factory production, much building construction takes place outdoors, is performed
within constrained and often physically challenging work areas, and is executed by a highly fragmented workforce. Despite the differences in these production environments, the construction industry is looking
to lessons learned in factory production for approaches to improving the quality and effi ciency of its own processes. Such so-called lean construction methods attempt to:

•  Eliminate wasteful activities
•  Structure the methods of production and the supply chain of materials and products to achieve the quickest and most reliable workfl  ow
•  Decentralize information and decision making so as to put control of construction processes into the
hands of those most familiar with the work and most capable of improving it

Current estimates of labor in efficiency in building construction run as high as 35 to 40 percent, and estimates of materials wastage are 20 percent or more. The challenge of lean construction is to restructure the way in which construction materials and building components are manufactured, delivered, and assembled so as to reduce these inefficiencies and improve the quality of the delivered product.

Improving Information Management
Developments in information technology also are infl uencing the way buildings are designed and con-
structed. Most notable is  building information modeling (BIM), the computerized, three-dimensional modeling of building systems. Unlike the two-dimensional representation of building systems characteristic of
conventional  computer-aided design (CAD), BIM involves an intelligent model. Components are not only represented geometrically, but are also linked to data describing their intrinsic properties and their relationships to other components. Originally developed for use in highly capital-intensive industries such as aerospace and automobile manufacturing, this modeling technology is now fi  nding increased application in the design and construction of buildings.

BIM has the potential to impact many aspects of the building life cycle. It can aid the design team with the visualization and realization of complex geometries. It can improve coordination between design
disciplines––for example, searching out “collisions” between mechanical system ductwork and structural framing or other such physical interferences between systems––and it can facilitate the modeling of building energy use and the performance of other building systems. For the builder,  BIM can be used to improve coordination of trades, to drive the automated fabrication or preassembly  of building components, and to integrate cost and schedule data more closely with building design. For the building owner, information accumulated in the model during design and construction can be carried forward for use with postconstruction building operations and facilities planning.

As the implementation of BIM matures, it is expected to have a profound impact as a communication tool used to improve the coordination and sharing of information among all of the parties to a project.

As the integrated building model is shared across the traditional boundaries of disciplines and project phases, the boundaries of responsibility between the designers, constructors, and owners will also blur, and
new, more integrated relationships between these parties will likely be required to fully enable the potential of this technology.