Technical drawing is an essential skill for quantity surveyors in Kenya, as it enables clear communication of design intent and accurate interpretation of construction components. Mastery of pictorial and orthographic drawings allows quantity surveyors to visualize and quantify building elements precisely, facilitating cost estimation, procurement, and project management. This chapter focuses on understanding the meanings, applications, and standards of pictorial and orthographic drawings within the quantity surveying profession.

4.1 Meaning of pictorial and orthographic drawings

In the Kenyan construction industry, quantity surveyors interact regularly with various forms of technical drawings. Pictorial and orthographic drawings serve different but complementary purposes in representing physical components and structures. Grasping their meanings and distinctions is vital for quantity surveyors to interpret project documentation accurately and produce reliable measurements and cost analyses.

4.1.1 Meaning of pictorial drawings

Pictorial drawings represent three-dimensional objects on a two-dimensional surface, providing a realistic view of components or assemblies. They help quantity surveyors and other stakeholders visualize the final appearance of a building element or structure without requiring advanced spatial imagination.

• Visual representation of 3D objects: Pictorial drawings depict height, width, and depth simultaneously, making it easier to understand complex shapes.
• Common types include isometric, oblique, and perspective drawings: Each type offers a different angle or distortion method to enhance clarity or realism.
• Useful for presentations and client communications: Quantity surveyors often use pictorials to explain design ideas or variations to clients unfamiliar with technical plans.
• Aid in identifying spatial relationships: They clarify how components fit together, which helps in assessing material quantities and site logistics.
• Support initial cost estimation: By providing a tangible view, pictorial drawings assist early-stage quantity takeoffs before detailed orthographic plans are available.

4.1.2 Meaning of orthographic drawings

Orthographic drawings are two-dimensional representations of three-dimensional objects, showing multiple views (usually front, top, and side) without perspective distortion. They form the backbone of construction documentation, enabling precise measurement and specification of components.

• Projection of object views onto perpendicular planes: Orthographic drawings systematically flatten the object into separate views to capture all dimensions.
• Standard views include plan, elevation, and section: These views reveal different aspects of the component’s shape and features.
• Conform to international and Kenyan standards (e.g., BS 8888, ISO 128): Compliance ensures uniform interpretation across teams and disciplines.
• Enable accurate dimensioning and detailing: Quantity surveyors rely on orthographic drawings to extract exact sizes and quantities of materials.
• Foundation for construction and fabrication: These drawings guide builders and suppliers with unambiguous instructions.

4.1.3 Differences between pictorial and orthographic drawings

Understanding the distinctions between these two drawing types helps quantity surveyors choose appropriate tools for communication and measurement tasks.

• Dimensional portrayal: Pictorial drawings show three dimensions in one view; orthographic drawings separate dimensions into multiple views.
• Purpose and usage: Pictorials emphasize visualization and conceptualization; orthographic drawings prioritize precision and technical specification.
• Level of detail: Orthographic drawings provide detailed dimensions and notes; pictorials usually lack scale and dimensioning.
• Interpretation skills required: Orthographic drawings require training to visualize multiple views as a single object; pictorials are more intuitive.
• Application in quantity surveying: Orthographic drawings are primary for quantity takeoff, while pictorials assist in stakeholder understanding and preliminary assessments.

4.1.4 Significance of pictorial and orthographic drawings in quantity surveying

Both drawing types are integral to the quantity surveying process, supporting different phases and functions in construction projects.

• Facilitate accurate measurement and estimation: Orthographic drawings provide the necessary data for precise quantity calculations.
• Enhance communication with non-technical stakeholders: Pictorial drawings bridge the understanding gap with clients and contractors.
• Support risk management: Clear drawings reduce misinterpretation and errors that could cause cost overruns or delays.
• Aid in value engineering: Visual and technical drawings enable evaluation of design alternatives for cost-effectiveness.
• Improve documentation and record keeping: Both drawing types contribute to comprehensive project files essential for audits and claims.

Chapter Summary

This chapter explored the fundamental concepts and techniques for producing pictorial and orthographic drawings, emphasizing their roles in accurately representing components. It began by defining pictorial drawings, which provide a three-dimensional view, and orthographic drawings, which depict multiple two-dimensional views of an object. The concept of sectioning was introduced to reveal internal features by cutting through components, enhancing clarity in complex designs. The chapter also covered the importance of symbols and abbreviations as standardized shorthand to convey detailed information efficiently. Practical procedures for drawing and interpreting orthographic elevations were explained, focusing on creating accurate front, side, and top views. Finally, the chapter addressed proper dimensioning methods to ensure that orthographic elevations communicate precise measurements for manufacturing or construction. Together, these topics build a comprehensive foundation for producing clear and professional technical drawings.