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The Basis of the Estimate

An estimate requires that there be a basis for that estimate – in other words, a document or set of documents that the estimator can use to derive the necessary tasks to determine the scope and value of the work. This document or set of documents will serve as a foundation for the estimate. Clearly, small projects may not require a full set of plans or specifications as an entire structure would. For small projects, one can develop a Scope of Work or Statement of Work (SOW) that identifies what the owner wants. Realistically, the documents that serve as the basis of the estimate run the full gamut from a single-page SOW to a fully developed, well-coordinated set of plans and specifications that identify in detail the scope of the project.

Estimating construction projects requires fluency in the language and symbols used in construction plans. This chapter provides an overview of a project's bid drawings. It does not offer detailed instruction in plan reading but reviews the organization of the plans and the information necessary for estimating. This chapter will also provide a glimpse into the contents necessary for SOW to be considered sufficient.

ROLE OF THE DRAWINGS IN ESTIMATING

The three terms most often used to refer to the graphic portion of the documents for a building project are:

• Plans
• Drawings
• Blueprints

While the last is a fairly antiquated term, plans are still frequently referred to as blueprints. For the purpose of this text, these terms are synonymous and can be used interchangeably. They are the graphic representation or illustration of the project and comprise the lines, symbols, and abbreviations printed on paper that represent the owner's wishes, as interpreted by the architect. The majority of plans today are black line drawings plotted on white sheets of paper of varying sizes. Plans are the quantitative representation of the project. Plans provide the information necessary to calculate lengths, areas, volumes, and quantities of individual items (counts) that serve as the basis of the take-off and ultimately the estimate. These plans combined with the technical specifications (discussed further in Chapter 2) will comprise the bid documents. If the project goes forward, the bid documents will become the contract documents and form the basis of the contract for construction.

DESIGN DEVELOPMENT

Most drawings develop over several generations of review and modification as a result of owner input, coordination with other design disciplines, building code compliance, and general fine-tuning. This process is referred to as design development, and it occurs before the release of the final version of drawings, called the working drawings. Working drawings are the completed design – a code-compliant representation of the project, ready for bidding and, ultimately, construction. They are the focus of this chapter and are the prerequisite for preparing a detailed unit price estimate. (Note: “Preliminary” drawings created early in the design development process may be used as a basis for budget estimates, but budget estimating requires specific skills of seasoned professional estimators who have years of experience developing unit price estimates. Preliminary drawings require that the estimator fill in the blanks as to what is not shown on the plans but is required for a complete estimate.)

The completed drawings become a “set” that incorporates all adjustments, changes, and refinements made by the architect or engineer as the final step in design development. Working drawings should comply with all applicable building codes, including any local ordinances having jurisdiction over the project. Drawings should include all the information one will need to prepare a detailed estimate and eventually build the project. The set of working drawings consists of various disciplines of design that use the architectural or core drawings as their basis. The core drawings illustrate the owner's desire or requirements as interpreted by the architect, or core design professional. Subconsultants such as the structural, mechanical, and electrical engineers will use the architect's drawings to create the structural, mechanical, and electrical engineering portion of the plan set to make the space habitable and functional. This assumes the project requires these other disciplines.

All buildings are constructed with a definitive purpose and require professionals skilled in specific areas to make the design suitable. Just as most contractors develop an expertise in one market type of construction (residential, light commercial, etc.), design professionals often focus on a general area of expertise. Examples include a commercial kitchen designer for restaurant kitchens, or an architect that specializes in the hospitality or medical industry. Specialty drawings, included as part of the set, often require considerable coordination with the mechanical and electrical systems, as well as with the core drawings. The coordination aspect of the design between subconsultants cannot be understated. This ensures that structural columns are not placed in door openings, or that mechanical equipment is provided with power to operate.

Other drawings in the set include designs that are less concerned with the structure itself than with support services, such as utilities, that will be provided to the structure. These civil or site drawings include grading and drainage plans, which indicate how surface precipitation will be channeled away from the structure and collected onsite; landscaping and irrigation design; paving; and curbing layout. Ordinary site improvements, such as pedestrian walkways, fencing, patios, walks, flagpoles, and the like, are shown on a kind of catchall site improvements drawing. In short, the civil drawings help integrate the building with the site it is built on.

Some drawings are crossovers and show items of work or systems that may also be found in another set. For example, site electrical drawings indicating site lighting, power distribution, and low-voltage wiring (cable TV, telephone, and data) may also be shown in the electrical portion of the set.

In addition to drawings that show actual architectural or engineering improvements, there are drawings that provide data only or show compliance with codes and ordinances. These will be explored later in this chapter.

ORGANIZATION OF THE WORKING DRAWINGS

There is a distinct organizational structure to the working drawings, which is almost universally accepted and is as follows:

• Architectural drawings: Core drawings showing the layout of the building and its use of space. They convey the aesthetic value of the structure and show the dimensions and placement of all key features. The first architectural drawings in a set generally show large areas in less detail. As one progresses through the architectural set, the level of detail increases. These drawings are prefixed by the letter “A” and sequentially numbered. The architectural drawings typically follow the civil drawings in the actual set.
• Structural drawings: Illustrate how the various load-carrying systems will transmit live and dead loads of the structure to the earth. Structural design is based on the architectural features and is designed around the core drawings. (For example, columns and beams are designed to avoid interrupting a space.) Structural drawings are prefixed by the letter “S” and are sequentially numbered. They often follow the architectural drawings in the set.
• Mechanical drawings: Illustrate the physical systems of a structure, such as plumbing, fire suppression/protection, and HVAC (heating, ventilating, and air-conditioning) systems. These drawings may be prefixed by the letter “M” for mechanical or “H” for heating. Plumbing drawings use the letter “P” and fire suppression drawings use “FP”(fire protection), “SP” (sprinkler system), or “F” (fire). All drawings are sequentially numbered and shown mainly in plan view with supporting details. Typically, the mechanical set follows the structural drawings in the set.
• Electrical drawings: Illustrate the electrical requirements of the project, including power distribution, lighting, and low-voltage specialty wiring, such as for fire alarms, telephone/data, and technology wiring. They often show the provision for power wiring of equipment illustrated on other types of drawings. They are prefixed by the letter “E” and are sequentially numbered. Electrical drawings follow the mechanical drawings in a set.
• Specialty drawings: Illustrate the unique requirements of various spaces' special uses (such as kitchens, libraries, retail spaces, and home theater systems). They define the coordination among other building systems, most commonly the mechanical and electrical systems. The drawings are sequentially numbered and named according to the type of drawings. For example, “K” might be used for kitchen drawings, “F” for fixture drawings, and so forth. Given the complexity of today's structures it is not uncommon to see more than one set of specialty drawings.
• Site or civil drawings: Illustrate the structure's relationship to the property, including various engineering improvements to the site, such as the sanitary system, utilities, paving, pedestrian walks, curbing, and so forth....