Engineering and Construction

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Dead loads are always present in a building; that is, they do not vary with time. They include the weights of the materials and components that comprise the structure. The dead load of a component is computed by multiplying its volume by the density of the material. Because both the densities and the dimensions of the components are known with reasonable accuracy, dead loads in a building can be estimated with greater certainty than other load types. Densities of some of the commonly used materials are given in  Table 2.


The dead load for which a building component is designed includes the self-load of the component plus the dead loads of all other components that it supports. For example, the dead load on a column includes the weight of the column itself plus all the dead load imposed on it. In Figure 3.3, the dead load on a column is the weight of the column plus the dead load from the beams and slab resting on it. Similarly, the dead load on a beam is the weight of the beam itself plus the dead load from the slab that it supports. The dead  load on the slab is only the self-weight of the slab. However, if the slab supports a floor finish, ceiling, light fixtures, or plumbing and electrical pipes, their weights must be included in the dead load acting on the slab.

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The general contractor will normally have an inspection process to ensure that the work of all subcontractors is progressing as indicated in the contract documents and that the work meets the standards of quality and workmanship. On smaller projects, this may be done by the project superintendent  . On large projects, a team of quality-assurance inspectors generally assists the contractor’s project superintendent. These inspectors are individuals who, by training and experience, are specialized in their own areas of construction—for example, concrete, steel, or masonry.


Additional quality control is required by the contract through the use of independent testing laboratories. For instance, structural concrete to be used on the site must be verified for strength and other properties by independent concrete testing laboratories.

Leaving quality control of materials and performance entirely in the hands of the contractor is considered inappropriate. It can render the owner vulnerable to omissions and errors in the work, and it places an additional legal burden on the contractor. Therefore, the owner usually retains the services of the project architect to provide a third-party level of scrutiny to administer the construction contract. If not, the owner will retain another independent architect, engineer, or inspector to provide construction contract administration services. The contracting community favors this third-party oversight of its work.

The architect’s role during the construction phase has evolved over the years. There was a time when architects provided regular supervision of their projects during construction, but the liability exposure resulting from the supervisory role became so adverse for the archi-tects that they have been forced to relinquish this responsibility. Instead, the operative term for the architect’s role during construction is   field observation  of the work.

The observational role still allows the architects to verify that their drawings and specifications are transformed into reality just as they had conceived. It also provides a sufficient safeguard against the errors caused by the contractors’ misinterpretation of contract documents in the absence of the architects’ clarification and interpretation. The shift in the architect’s role to observer of construction also recognizes the important and entirely independent role that the contractor must play during construction. This rec-ognition provides full authority to the general contractor to proceed with the work in the manner that the contractor deems appropriate. This reinforces the earlier statements that:

•    The architect determines the   what  and   where . 
•    The contractor determines the   how  (means and methods) and   when  (sequence) of construction.

In other words, daily supervision or superintendence of construction is the function of the contractor—the most competent person to fulfill this role. The architect provides periodic observation and evaluation of the contractor’s work and notifies the owner if the work is not in compliance with the intent of the contract documents. This under-scores the  division between the responsibilities of the architect and the contractor during construction.

Note that by providing observation, the architect does not certify the contractor’s work. Nor does the observation relieve the contractor of its responsibilities under the contract. The contractor remains fully liable for any error that has not been discovered through the architect’s observation. However, the architect may be held liable for all or part of the work observed, should the architect fail to detect or provide timely notification of work not conforming with the contract documents. This omission is known as failure to detect.
 
Because many components can be covered up by other items over days or hours, the architect should visit the construction site at regular intervals, as appropriate to the progress of construction. For example, earthwork covers foundations and underground plumbing, and gypsum board covers ceiling and wall framing. Observing the work after the components are hidden defeats the purpose of observation.

On some projects, a resident project architect or engineer may be engaged by the architect, at an additional cost to the owner, to observe the work of the contractor. Under the conditions of the contract, the contractor is generally required to provide this person with an on-site office, water, electricity, a telephone, and other necessary facilities.

INSPECTION OF WORK 

There are only two times during the construction of a project that the architect makes an exception to being an observer of construction. At these times, the architect inspects the work. These inspections are meant to verify the general contractor’s claim that the work is (a) substantially complete and (b) has been completed and hence is ready for final payment. These inspections, explained in Section 1.10, are referred to as:

•     Substantial  completion   inspection
•    Final  completion  inspection

PAYMENT CERTIFICATIONS 

In addition to construction observation and inspection, there are several other duties the architect must discharge in administering the contract between the owner and the contractor. These are outlined in the box “Summary of Architect’s Functions as Construction Contract Administrator.” Certifying (validating) the contractor’s periodic requests for payment against the work done and the materials stored at the construction site is perhaps the most critical of these functions. An application for payment (typically made once a month unless stated differently in the contract) is followed by the architect’s evaluation of the work and necessary documentation to verify the contractor’s claim. Because the architect is not involved in day-to-day supervision, the issuance of the certificate of payment by the architect does not imply acceptance of the quality or quantity of the contractor’s work. However, the architect has to be judicious and impartial to both the owner and the contractor and perform within the bounds of the contract. 

CHANGE ORDERS 

There is hardly a construction project that does not require changes after construction has begun. The contract between the owner and the contractor recognizes this fact and includes provisions for the owner’s right to order a change and the contractor’s obligation to accept the   change order  in return for an equitable price adjustment. Here again, the architect performs a quasi-judicial role to arrive at a suitable agreement and price between the owner and the contractor.    

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Once the general contractor has been selected and the contract awarded, the construction work begins, as described in the   contract documents  . The contract documents are virtually the same as the bidding documents, except that the contract documents are part of a signed legal contract between the owner and the contractor. They generally do not contain Division 00 of the MasterFormat.

In preparing the contract documents, the design team’s challenge is to efficiently produce the graphics and text that effectively communicate the design intent to the construction professionals and the related product suppliers and manufacturers so that they can do the following:

  •    Propose accurate and competitive bids
  •    Prepare detailed and descriptive submittals for approval
  •    Construct the building with a minimum number of questions, revisions, and changes
   
SHOP DRAWINGS

The construction drawings and the specifications should provide a fairly detailed delineation of the building. However, they do not describe it to the extent that fabricators can produce building components directly from them. Therefore, the fabricators generate their own drawings, referred to as   shop drawings , to provide the higher level of detail necessary to fabricate and assemble the components.

Shop drawings are not generic, consisting of manufacturers’ or suppliers’ catalogs, but  are specially prepared for the project by the manufacturer, fabricator, erector, or subcontractors. For example, an aluminum window manufacturer must produce shop drawings to show that the required windows conform with the construction drawings and the specifications. Similarly, precast concrete panels, stone cladding, structural steel frame, marble or  granite flooring, air-conditioning ducts, and other components require shop drawings  before they are fabricated and installed.

Before commencing fabrication, the fabricator submits the shop drawings to the general  contractor. The general contractor reviews them, marks them “approved,” if appropriate, and then submits them to the architect for review and approval. Subcontractors or   manufacturers cannot submit shop drawings directly to the architect.

The review of all shop drawings is coordinated through the architect, even though they may actually be reviewed in detail by the appropriate consultant. Thus, the shop drawings pertaining to  structural components are sent to the architect and then to the structural consultant for review and approval. The fabricator generally begins fabrication only after receiving the architect’s review of the shop drawings.

The review of shop drawings by the architect is limited to checking that the work indicated therein conforms with the overall design intent shown in the contract documents. Approval of shop drawings that are later discovered to deviate from the  contract documents does not absolve the general contractor of the responsibility to comply with the contract documents for quality of materials, workmanship, or the dimensions of the fabricated components,  Figure  1.9.


MOCK-UP SAMPLES

In addition to shop drawings, full-size mock-up samples of one or more critical elements of the building may be required in some projects. This is done to establish the quality of materials and workmanship by which the completed work will be judged. For example, it is not unusual for the architect to ask for a mock-up of a  typical area of the curtain wall of a high-rise building before the fabrication of the actual curtain wall is undertaken. Mock-up samples go through the same approval process as the shop drawings.

OTHER SUBMITTALS

In addition to shop drawings and any mock-up samples, some other submittals required from the contractor for the architect’s review are:

•   Product  material  samples 
•   Product  data 
•   Certifications
•   Calculations

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Invitational bidding, also called   closed bidding , is another variation of the DBB method that is generally used for quasi-public and some private projects. In this method, the owner preselects general contractors who have demonstrated, based on their experience, resources, and financial standing, their qualifications to perform the work. The selected contractors are then invited to bid for the project, and the contractor with the lowest bid is then awarded the contract. The architect (as the owner’s representative) may be involved in the prescreening process.

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This method is very similar to competitive sealed bidding and is commonly used for publicly funded projects. The difference between competitive sealed bidding and competitive sealed proposal methods is that the owner’s selection of the general contractor is not based on price alone but also on such other criteria as the contractor’s past experience, safety record, proposed personnel, project schedule, and so on. To ensure fairness, the advertisement and bidding documents must provide the details of the selection criteria, with relative weightings assigned to each criterion.  

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On several publicly funded projects, the award of a construction contract to the general contractor is based on   competitive sealed bidding , also called   open bidding . This refers to the process by which qualified contractors are invited to bid on the project. The invitation is generally issued through advertisements in newspapers, trade publications, and other public media.

The advertisement for bids includes a description of the project, its location, where to obtain the bidding documents, the price of the bidding documents, the bid opening date and location, and other important information. The purpose of the advertisement is to notify and thereby attract a sufficient number of contractors to compete for the construction contract.

The general contractor’s bid for the project is based on the information provided in the bidding documents . The bidding documents are essentially the construction document set with such additional items as the instructions to bidders, requirements with respect to the  financial and technical status of bidders (see the information on surety bonds in the box  “Expand Your Knowledge”), and the contract agreement form that the successful bidder  will sign when the contract is awarded. Because these additional items are text items, they  are bound together as a project manual, Figure 1.8.

FIGURE 1.8  The project manual in the bidding document set includes specifications and   Division 00. After the general contractor has been selected, the project manual (in the contract document set) generally excludes Division 00.

In the competitive sealed bidding method, the bidding documents are generally given only to contractors who are capable, by virtue of their experience, resources, and financial standing, to bid for the project. Therefore, the architect (as the owner’s representative) may prescreen the bidders with respect to their reputation and ability to undertake the project.


An exception to prescreening for the release of bidding documents involves projects funded by the federal, state, or local government, for which almost anyone can access the bidding documents. However, even in this kind of project, the number of contractors who can actually submit the bids is practically limited. This limitation is generally the result of the financial security required from the bidders, known as a   bid bond . The bidder must obtain a bid bond from a surety company in the amount specified in the bidding documents. This bond is issued based on the contractor’s experience, ability to perform the work, and financial resources required to fulfill the contractual obligations.

Whether or not the release of the bidding documents is restricted, the procedure stated earlier ensures that all the bidders are similarly qualified with respect to financial ability, experience, and technical expertise. Because all bidders receive the same information and are of the same standing, the competition is fair; therefore, the contract is generally awarded to the lowest qualified bidder.    

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In the design-bid-build method, the general contractor is selected through competition. The owner obtains multiple bids for the project from which the general contractor, who provides the “best value for money,” is selected. Within this overall approach, several  versions are available to suit the requirements of the project and the particular needs of  the owner. Collectively, these delivery versions are referred to as the   design bid-build  (DBB) method because in this version, the design, bid, and construction phases of a  project are sequential, and one phase does not begin until the previous phase has been  completed,  Figure 1.7 . Following are three commonly used versions of the DBB method  of delivery:

  •    DBB method—competitive sealed bidding (open bidding)
  •    DBB method—competitive sealed proposal
  •    DBB  method— invitational  bidding   (closed  bidding)  

FIGURE 1.7  Sequence of operations in the design-bid-build (DBB) method of project delivery. Note that the owner’s approval is required before proceeding from one phase or stage to the next.

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Selecting the general contractor is a crucial part of a project. A number of selection methods exist. The method used in selecting the general contractor, its timing, and the contractor’s obligations under the contract distinguishes one project delivery method from the other. Some of the most commonly used delivery methods are:

•    Design-bid-build  method
•    Design-negotiate-build  method
•    Construction manager as agent method
•     Construction  manager  at  risk   method
•    Design-build  method
•    Integrated  project  delivery  method

The design-bid-build method is the oldest and most familiar method of project delivery. This method is covered first. Because the essential features of construction and postconstruction phases are almost identical in all delivery methods, a discussion of what is included in these two phases is presented next. Subsequently, other methods are discussed in terms of how they differ from the design-bid-build method. The table “Project Delivery Methods at a Glance” provides a synopsis of these methods.

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The preconstruction phase generally begins after the construction drawings and specifications have been completed and culminates in the selection of the construction team. The construction of even a small building involves so many specialized skills and trades that the work cannot normally be undertaken by a single construction firm. Instead, the work is generally done by a team consisting of the   general contractor  and a number of specialty subcontractors .

Thus, a project may have roofing; window and curtain wall; plumbing; and heating, ventilation, and air-conditioning (HVAC) subcontractors, among others, in addition to the general contractor. The general contractor’s own work may be limited to certain components of the building (such as the structural components—load-bearing walls, reinforced concrete beams and columns, roof and floor slabs, etc.), with all the remaining work subcontracted.

In contemporary projects, however, the trend is toward the general contractors not performing any actual construction work but subcontracting the work entirely to various sub-contractors. Because the subcontractors are contracted by the general contractor, only the general contractor is responsible and liable to the owner.

In some cases, a subcontractor will, in turn, subcontract a portion of his or her work  to another subcontractor, referred to as a   second-tier subcontractor, Figure 1.6. In  that  case, the general contractor deals only with the subcontractor, not the second-tier subcontractor.

Whether the general contractor performs part of the construction work or subcontracts  the entire work, the key function of the general contractor is the overall management of  construction. This includes coordinating the work of all subcontractors, ensuring that the  work done by them is completed in accordance with the contract documents, and ensuring  the safety of all workers on the site. A general contractor with a good record of site safety  not only demonstrates respect for the workers but also improves the profit margin by lowering the cost of construction insurance.

FIGURE 1.6  Members of the construction team and their interrelationships with each other and the owner. A solid line in this illustration indicates a contractual relationship between parties. A dashed line indicates a communication link, not a contract. The relationships shown here are not absolute and may change with the nature of the project.

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Architectural design typically involves Divisions 2 to 14 of the Facilities Construction Subgroup. Although the basis for sequencing the Divisions in this subgroup is far more complicated, the first few divisions (those that are used in virtually all buildings) may be deduced by visualizing the sequence of postearthwork operations required in constructing the simple building shown in  Figure 1.5. The building consists of load-bearing masonry walls, steel roof joists, and wood roof deck.

FIGURE 1.5  A simple load-bearing masonry wall building with steel roof trusses and wood roof deck used as an aid to recalling the sequence of the first few (architecturally important) divisions of the MasterFormat.

The first operation is the foundations for the walls. Because foundations are typically made of concrete,   Concrete  is Division 03. After the foundations have been completed, masonry work for the walls can begin. Thus,   Masonry  is Division 04. After the walls are completed, steel roof joists can be placed. Thus, Division 05 is   Metals . The installation of the wood roof deck follows that of the steel joists. Hence,   Wood, Plastics, and Composites is Division 06.


After the roof deck is erected, it must be insulated and protected against weather. Therefore,   Thermal and Moisture Protection  is Division 07. Roofing and waterproofing (of basements) are part of this division, as are wall insulation and joint sealants. The next step is to protect the rest of the envelope; hence, Division 08 is   Openings . All doors and windows are part of this division, regardless of whether they are made of steel, aluminum, or wood.

With the envelope protected, finish operations, such as those involving the interior dry- wall, flooring, and ceiling, can begin. Thus, Division 09 is   Finishes . Division 10 is Specialties , which consists of several items that cannot be included in the previous divisions, such as toilet partitions, lockers, storage shelving, and movable partitions.

Obviously, the building must now receive all the necessary office, kitchen, laboratory, or other equipment. Thus, Division 11 is   Equipment . Division 12 is   Furnishings ,  followed  by Special Construction  (Division 13) and   Conveying Equipment   (Division  14).   

Before any construction operation can begin, there must be references to items that apply to all divisions, such as payment procedures, product-substitution procedures, contract-modification procedures, contractor’s temporary facilities, and regulatory requirements imposed by the city or any other authority having jurisdiction. This is Division 01, General Requirements  . Division 00 (  Procurement and Contracting  Requirements  ) refers to the requirements for the procurement of bids from prospective contractors.

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Architectural design typically involves Divisions 2 to 14 of the Facilities Construction Subgroup. Although the basis for sequencing the Divisions in this subgroup is far more complicated, the first few divisions (those that are used in virtually all buildings) may be deduced by visualizing the sequence of postearthwork operations required in constructing the simple building shown in  Figure 1.5   . The building consists of load-bearing masonry walls, steel roof joists, and wood roof deck.

FIGURE 1.5 A simple load-bearing masonry wall building with steel roof trusses and wood roof deck used as an aid to recalling the sequence of the first few (architecturally important) divisions of the MasterFormat.

The first operation is the foundations for the walls. Because foundations are typically  made of concrete,   Concrete  is Division 03. After the foundations have been completed, masonry work for the walls can begin. Thus,   Masonry  is Division 04. After the walls are completed, steel roof joists can be placed. Thus, Division 05 is   Metals . The installation of the wood roof deck follows that of the steel joists. Hence,   Wood, Plastics, and Composites is Division 06.

After the roof deck is erected, it must be insulated and protected against weather. Therefore,   Thermal and Moisture Protection  is Division 07. Roofing and waterproofing (of basements) are part of this division, as are wall insulation and joint sealants. The next step is to protect the rest of the envelope; hence, Division 08 is   Openings . All doors and windows are part of this division, regardless of whether they are made of steel, aluminum, or wood.

With the envelope protected, finish operations, such as those involving the interior dry-wall, flooring, and ceiling, can begin. Thus, Division 09 is   Finishes . Division 10 is   Special-
ties , which consists of several items that cannot be included in the previous divisions, such
as toilet partitions, lockers, storage shelving, and movable partitions.

Obviously, the building must now receive all the necessary office, kitchen, laboratory, or other equipment. Thus, Division 11 is   Equipment . Division 12 is   Furnishings ,  followed  by  Special Construction  (Division 13) and   Conveying Equipment   (Division  14).   

Before any construction operation can begin, there must be references to items that  apply to all divisions, such as payment procedures, product-substitution procedures, contract-modification procedures, contractor’s temporary facilities, and regulatory requirements imposed by the city or any other authority having jurisdiction. This is Division 01, General Requirements  . Division 00 (  Procurement and Contracting  Requirements  ) refers to the requirements for the procurement of bids from prospective contractors.

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Just as the construction drawings are prepared separately by the architect and each consultant for their respective portions of the work, so are the specifications. The specifications from various design team members are assembled by the architect in a single document called the   project manual . Because the specifications consist of printed (typed) pages (not graphic images), a project manual is a bound document—like a book.

The major component of a project manual is the specifications. However, the project manual also contains other items, as explained later in this chapter.

The set of construction drawings (from various design team members) and the project manual together constitute what is known as the   construction document set, Figure 1.3. The construction document set is the document that the owner and architect use to invite bids from prospective contractors.

FIGURE 1.3 A construction document set consists of a set of architectural and consultants’ construction drawings plus the project manual. The project manual is bound in a book format.

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Buildings cannot be constructed from drawings alone, because there is a great deal of information that cannot be included in the drawings. For instance, the drawings will give the locations of columns, their dimensions, and the material used (such as reinforced concrete), but the quality of materials, their properties (the strength of concrete, for example), and the test methods required to confirm compliance cannot be furnished on the drawings. This information is included in the document called   specifications. 

Specifications are written technical descriptions of the design intent, whereas the drawings provide the graphic description. The two components of the construction documents—the specifications and the construction drawings—complement each other and generally deal with different aspects of the project. Because they are complementary, they  are supposed to be used in conjunction with each other. There is no order of precedence between the construction drawings and the specifications. Thus, if an item is described in  only one place—either the specification or the drawings—it is part of the project, as if  described in the other.

For instance, if the construction drawings do not show the door hardware (hinges, locks, handles, and other components) but the hardware is described in the specifications, the owner will get the doors with the stated hardware. If the drawings had precedence over the specifications, the owner would receive doors without hinges and handles.

Generally, there is little overlap between the drawings and the specifications. More importantly, there should be no conflict between them. If a conflict between the two documents is identified, the contractor must bring it to the attention of the architect promptly. In fact, construction contracts generally require that before starting any portion of the project, the contractor must carefully study and compare the drawings and the specifications and report inconsistencies to the architect.

If the conflict between the specifications and the construction drawings goes unnoticed initially but later results in a dispute, the courts have in most cases resolved it in favor of the specifications—implying that the specifications, not the drawings, govern the project. However, if the owner or the design team wishes to reverse the order, it may be so stated in the owner-contractor agreement.

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During the CD stage, the architect and consultants prepare their own sets of drawings, referred to as   construction drawings . Thus, a project has architectural construction drawings, civil and structural construction drawings, MEPF construction drawings, landscape construction drawings, and so on.

Construction drawings are dimensioned drawings (usually computer generated) that  fully delineate the building. They consist of floor plans, elevations, sections, schedules, and  various large-scale details. The details depict a small portion of the building that cannot be  adequately described on smaller-scale plans, elevations, or sections.    

Construction drawings are the drawings that the construction team uses to build the  building. Therefore, they must indicate the geometry, layout, dimensions, types of materials, details of assembling the components, colors and textures, and so on. Construction drawings are generally two-dimensional drawings, but three dimensional isometrics are sometimes used for complex details. Construction drawings are also used by the contractor to prepare a detailed cost estimate of the project at the time of bidding.

Construction drawings are not a sequence of assembly instructions, such as for a bicycle. Instead, they indicate what every component is and where it will be located when the building is completed. In other words, the design team decides the “what” and “where” of the building. The “how” and “when” of the building are entirely in the contractor’s domain.

NOTE

Working Drawings and Construction Drawings The term working drawings was used until the end of the  twentieth century for what are now commonly referred to as construction drawings.

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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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During the   predesign phase  (also called the   planning phase  ), the project is defined in terms of its function, purpose, scope, size, and economics. This is the most crucial of the five phases, and is almost always managed by the owner and the owner’s team. The success or failure of the project may depend on how well this phase is defined, detailed, and managed. Obviously, the clearer the project’s definition, the easier it is to proceed to the subsequent phases.

Some of the important predesign tasks are:

•    Building program definition
•    Economic feasibility assessment,  including the project’s overall budget and financing
•    Site assessment and selection,  including verifying the site’s appropriateness and determining its designated land use
•    Governmental constraints assessment,   for example, building code and zoning constraints and other legal aspects of the project
•    Sustainability rating —whether the owner would like the project to achieve the U.S. Green Building Council’s (USGBC’s) Leadership in Energy and Environmental Design (LEED) certification at some level
•    Design team selection

BUILDING (PROJECT) PROGRAM 

This includes defining the activities, functions, and spaces required in the building, along with their approximate sizes and their relationships with each other. For a house or another small project, the programis usually simple and can be developed by the owner without external assistance. For a large project, however,where the owner may be an institution (such as a corporation, school board, hospital, religious organization, or governmental entity), developing the program may be a complex exercise. This may be due to the size and complexity of the project or the need to involve several individuals—a corporation’s board  of directors, for example—in decision making. These constituencies may have different views of the project, making it difficult to create a consensus.

Program development may also be complicated by situations in which the owner has a fuzzy idea of the project and is unable to define it clearly. By contrast, experienced owners tend to have a clear understanding of the project and generally provide a detailed, unambiguous program to the architect.

It is not unusual for the owner to involve the architect and a few other consultants of the design team in preparing the program. In this instance, the design team may be hired during the predesign phase. When the economic considerations of the project are paramount, the owner may also consult a construction cost analyst.

Whatever the situation, preparing the program is the first step in the project delivery process. It should be spelled out in writing and in sufficient detail to guide the design, reduce the liability risk for the architect, and avoid its misinterpretation. If a revision is made during the progress of the project, the owner’s written approval is necessary.

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The process by which a building project is delivered to its owner may be divided into the following five phases, referred to as the   project delivery phases . Although there is usually some overlap between adjacent phases, they generally follow this order:

  •     Predesign  phase
  •     Design  phase
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Estimate the depth of wood rafters on the basis of the horizontal (not slope) distance from the outside wall of the building to the ridge board in a gable or hip roof and the horizontal distance between supports in a shed roof. A 2 X 4 rafter spans approximately 7 feet (2.1 m), a 2 X 6 10 feet (3.0 m), a 2 8 14 feet (4.3 m), and a 2 X 10 17 feet (5.2 m).

The depth of wood light roof trusses is usually based on the desired roof pitch. A typical depth is one-quarter of the width of the building, which corresponds to a 6/ 12 pitch in a gable truss. Trusses are generally spaced 24 inches (600 mm) o.c. and can span up to approximately  65 feet (20 m).

Estimate the depth of wood floor joists as follows: 2 x 6 joists span up to 9 feet (2.7 m), 2 x 8 joists 11 feet (3.4 m), 2 x 10 joists 14 feet (4.3 m), and 2 x 12 joists 17 feet (5.2 m).

Estimate the depth of manufactured  wood I-joists as follows: 9½-inch (240-mm) joists span 16 feet (4.9
m), 117 /8 -inch (300-mm) joists 19 feet (5.8 m), 14-inch (360-mm) joists span 23 feet (7.0 m), and 16-inch (400-mm) joists span 25 feet (7.6 m).

Estimate the depth of  wood floor  trusses as 1/ 18 of their span. Typical depths of ß oor trusses range from 12 to 28 inches (305-710 mm) in 2-inch (51-mm) increments.

2 X 4 wood studs 24 inches (600 mm) o.c. can support attic and roof loads only. Either 2 X 4 studs 16 inches (400 mm) o.c. or 2 6 studs 24 inches o.c. can support one floor plus attic and roof. 2 X 6 studs 16 inches o.c. can support two ß oors plus attic and roof.

Framing members in light frame buildings are usually spaced either 16 or 24 inches (400 or 600 mm) o.c. For actual sizes of dimension lumber in both conventional and metric units, see Figure 3.22.

These approximations are valid only for purposes of preliminary building layout and must not be used  to select final member sizes. They apply to the normal range of building occupancies such as residential, office, commercial, and institutional buildings. For manufacturing and storage buildings, use somewhat larger  members.

Figure 3.22 The relationship between nominal and actual dimensions for the most common sizes of kiln-dried lumber is given in this simplified chart