Performing superstructure works is a crucial phase in building construction that directly affects the structural integrity and longevity of a building. For quantity surveyors in Kenya, understanding the technical processes involved in superstructure works enables accurate cost estimation, progress monitoring, and quality assurance. This chapter focuses on setting out the superstructure, concrete works including columns, slabs, beams, formwork, reinforcement, and curing practices that ensure durability and compliance with Kenyan construction standards.

3.1 Setting out superstructure works

Setting out is the process of transferring the building design from the drawings to the ground, marking the exact locations where structural elements will be constructed. For quantity surveyors, precise setting out is essential to quantify materials accurately and identify potential design or site conflicts early. In Kenyan construction projects, such as county government office buildings, errors in setting out can lead to costly rework and delays.

3.1.1 Purpose and importance of setting out

The purpose of setting out is to provide a physical reference for construction teams that aligns exactly with the architectural and structural plans. Its importance includes:

• Ensuring dimensional accuracy: Correct positioning prevents structural misalignment, which can compromise stability and aesthetics.
• Facilitating coordination: Clear layout points help different trades work efficiently without clashes.
• Reducing wastage: Accurate measurements minimize excess material orders, saving costs.
• Supporting quality control: Survey data helps verify compliance with design specifications.
• Enabling progress tracking: Quantity surveyors rely on setting out benchmarks to measure work advancement during site visits.

3.1.2 Tools and equipment used in setting out

The tools for setting out superstructure works must provide precision and durability under Kenyan site conditions. Common tools include:

• Theodolite: Measures horizontal and vertical angles for accurate positioning.
• Total Station: Combines electronic distance measurement and angular readings for detailed site layout.
• Measuring tapes and steel rulers: Basic tools for short distance verification.
• Plumb bobs and spirit levels: Ensure vertical and horizontal alignment of setting points.
• Marking materials: Paint, pegs, and string lines indicate exact locations on the ground.

3.1.3 Procedures for setting out superstructure works

Setting out follows a systematic sequence to transfer design points accurately:

1. Review design drawings: Verify all dimensions and structural elements relevant to the superstructure.
2. Establish control points: Use existing site benchmarks or create new ones with GPS or total stations.
3. Mark grid lines: Set perpendicular baseline lines using string and pegs based on control points.
4. Locate column positions: Measure from grid lines to mark column centres with stakes or paint.
5. Check levels and elevations: Use spirit levels or laser levels to confirm vertical positioning.
6. Record measurements: Document all set out data for verification and future reference.

3.1.4 Challenges in setting out and mitigation strategies

Setting out can face several challenges that affect accuracy and timeliness:

• Uneven terrain: Slopes and irregular ground surfaces complicate marking; use laser levels and adjust stakes accordingly.
• Weather conditions: Rain or strong winds can wash away markings; apply durable paint and secure pegs firmly.
• Human error: Misreading measurements leads to errors; cross-check dimensions with multiple tools and personnel.
• Obstructions: Existing site structures may block access; plan alternative routes and use GPS for indirect measurements.
• Communication gaps: Misunderstandings between surveyors and builders cause mistakes; hold regular coordination meetings to clarify points.

Chapter Summary

This chapter covers the essential processes involved in performing superstructure works, beginning with the precise setting out of superstructure elements to ensure accurate construction alignment. It details the concrete works for columns, suspended slabs, and beams, emphasizing proper formwork, reinforcement placement, and curing techniques to achieve structural integrity. The chapter highlights sustainability initiatives in concrete building elements, exploring alternative cementitious materials such as fly ash, slag cement, silica fume, and calcined clay, including innovations like high-performance and self-healing concrete. Superstructure walling is examined with attention to functional requirements, various wall construction methods and materials, damp proofing, and emerging green building practices including smart walls and modular construction. Roof construction is explained through its functional requirements, material selection, types, and step-by-step construction procedures. The discussion extends to roof covers, covering traditional and modern materials, underlays, installation methods, and sustainability considerations like energy efficiency and water harvesting. Finally, the installation of rainwater goods such as gutters, downpipes, channels, and fulbora is addressed to ensure proper water management in building structures.