What the syllabus asks you to cover
Construction Technology: Brick Masonry, Stone Masonry, Carpentry, Painting, Plastering, Concrete Roofing, Flooring, Damp Proof Course Building By-Laws
Standards and rules: these are study notes, not a current code or legal reference. Check the applicable edition, amendments, units and design assumptions before using a numerical limit or rule.
Introduction to Building Technology
- Building Technology encompasses the practical methods, techniques, and processes used to assemble and construct buildings and structures from foundation to finish
- It bridges the gap between architectural design and physical reality, translating drawings into durable, functional, and safe habitats
- This unit delves into the core construction technologies for key structural and finishing elements—masonry, carpentry, concrete work, and protective finishes
- It also covers the crucial regulatory framework of Building By-Laws, which govern all construction activity to ensure public safety, health, and orderly urban development
1. Construction Technology
1.1 Brick Masonry
- Definition: The systematic arrangement of bricks bonded together with mortar to form a unified mass that can carry loads, enclose space, and provide shelter
- Materials:
- Bricks: As per IS 1077
- Should be well-burnt, uniform, and free from cracks
- Mortar: Usually cement-sand mortar (1:4 to 1:6) for load-bearing walls
- Lime mortar or cement-lime mortar may be used for specific applications
- Key Terms:
- Course: A horizontal layer of bricks
- Header: A brick laid with its shorter face (head) exposed
- Stretcher: A brick laid with its longer face (stretcher) exposed
- Bond: The pattern in which bricks are arranged to interlock and avoid continuous vertical joints
- Types of Bonds:
- Stretcher Bond: All bricks laid as stretchers
- Used for half-brick (9" or 4.5") thick walls (partition walls)
- Header Bond: All bricks laid as headers
- Used for curved walls or footings
- English Bond: Alternate courses of headers and stretchers
- Strongest bond for walls one brick (9") thick or more
- Queen closers are used next to quoin headers
- Flemish Bond: Alternate header and stretcher in the same course
- More aesthetic but slightly weaker than English bond
- Rat-Trap Bond: Bricks laid on edge creating a cavity within the wall
- Provides thermal insulation and material economy
- Joints & Pointing:
- Raked Joint: Mortar raked out to a depth of 10-15mm to provide a key for plaster
- Flush Joint: Mortar finished flush with the brick face
- Pointing: The process of finishing mortar joints exposed to weather
- Types include flush, recessed, weathered, and struck pointing
- Construction Principles:
- Soaking: Bricks should be soaked in water to prevent them from absorbing water from the mortar, which weakens the bond
- Laying: Mortar bed should be uniform (approx. 10mm thick)
- Each brick should be properly pressed and leveled
- Plumb & Level: Walls must be checked constantly for verticality (plumb) and horizontal alignment (level)
- Construction Joints: Should be stepped (toothed) to provide a proper bond for future construction
1.2 Stone Masonry
- Definition: Construction of structures using dressed or undressed stones bonded with mortar
- Classification:
- Based on Dressing:
- Rubble Masonry: Stones of irregular size and shape
- Uncoursed/Random Rubble: Stones laid without forming continuous horizontal joints
- Coursed Rubble: Stones are roughly leveled to form courses
- Ashlar Masonry: Dressed stones with precise, rectangular shapes
- Ashlar Fine: Perfectly dressed, thin mortar joints
- Ashlar Rough Tooled: Face is rough-tooled, edges are dressed
- Based on Mortar:
- Dry Stone Masonry: No mortar
- Stones interlocked by skillful placement (e.g., retaining walls)
- Based on Dressing:
- General Principles:
- Stones should be hard, durable, and free from defects
- Bedding planes should be laid perpendicular to the direction of pressure
- Proper bonding through headers (bond stones) extending the full thickness of the wall is essential
- Quoins (corner stones) should be larger and stronger
- Through stones or bonding timbers are used at intervals in thick walls
1.3 Carpentry
- Definition: The skilled trade of cutting, shaping, joining, and installing wood for building construction and fixtures
- Timber Used: Seasoned and well-preserved timber (Teak, Sal, Pine, Deodar)
- Essential Joints:
- Lap Joint: Simple overlapping of members
- Mortise and Tenon Joint: A tenon (projection) on one piece fits into a mortise (hole) on another
- Strong and widely used for framing
- Dovetail Joint: Interlocking wedged shape
- Extremely strong in tension, used for drawer construction
- Bridle Joint: An open mortise and tenon
- Butt Joint: End of one member butts against the face of another, secured with fasteners (nails, screws)
- Weakest common joint
- Fasteners:
- Nails: Wire nails, concrete nails
- Screws: Provide better clamping force than nails
- Bolts & Nuts: For heavy connections
- Connectors: Metal plates, joist hangers, framing anchors
- Common Applications in Building:
- Formwork/Shuttering: Temporary molds for casting concrete
- Doors & Windows: Frames (chaukhat) and shutters
- Roof Trusses: For pitched roofs
- Flooring & Ceiling: Joists, planks, and panels
- Cabinetry & Furniture
1.4 Painting
- Purpose: To protect the surface from weathering, corrosion, and decay, and to provide a decorative, cleanable finish
- Sequence of Operations:
- Surface Preparation: Most critical step
- New Wood: Knotting (sealing knots), priming
- New Plaster/Concrete: Must be completely dry (seasoning), alkalinity neutralized, surface smoothed
- Metal: Rust removal, priming with anti-corrosive primer (e.g., red oxide)
- Priming (First Coat): Seals the surface, provides a base for subsequent coats, improves adhesion
- Undercoating (Second Coat): Provides opacity (hiding power) and builds up film thickness
- Finishing Coat (Final Coat): Provides the final color, gloss, and texture
- Types of Paints:
- Oil Paint: Traditional, durable, slow-drying
- Emulsion Paint (Latex): Water-based, fast-drying, easy application, popular for walls
- Enamel Paint: Hard, glossy, washable finish for wood and metal
- Cement Paint: For exterior masonry surfaces
- Distemper: Cheap, water-based, for interior plaster walls (less durable than emulsion)
- Defects in Painting:
- Blistering: Formation of bubbles due to trapped moisture or solvent
- Flaking/Peeling: Detachment of paint film due to poor adhesion
- Chalking: Powdering of the surface due to weathering of binder
- Running/Sagging: Paint runs down due to excessive thickness or thin consistency
1.5 Plastering
- Definition: The process of covering rough walls, ceilings, and other surfaces with a plastic mortar (plaster) to provide a smooth, durable, and protective finish
- Objectives: To protect the surface from atmospheric influences, conceal defective workmanship, provide a base for painting, and improve aesthetics
- Mortar Composition:
- Cement Mortar: Cement-sand (1:3 to 1:6)
- For external and wet areas
- Lime Mortar: Fat lime and sand (1:2)
- Slow setting, flexible
- Cement-Lime Mortar: Cement, lime, sand (e.g., 1:1:6)
- Combines strength of cement and workability of lime
- Procedure:
- Surface Preparation: Clean, wet the surface (to prevent suction)
- Application of Undercoat (Rendering): First coat, 10-15mm thick, applied and scratched to provide key for next coat
- Application of Finishing Coat: Thin coat (3-5mm) of finer mortar, troweled to a smooth finish
- Curing: Kept moist for at least 7 days to ensure proper hydration and prevent cracking
- Types of Finishes:
- Smooth Cast Finish: Smooth troweling
- Rough Cast Finish (Spatter Dash): Coarse aggregate thrown onto final coat for texture
- Pebble Dash: Small pebbles pressed into finishing coat
- Gypsum Plaster: Pre-mixed, provides a very smooth finish, sets quickly
1.6 Concrete Roofing (RCC Slab Construction)
- Definition: Construction of a horizontal structural element (slab) using Reinforced Cement Concrete to form the roof/floor of a building
- Components:
- Concrete: Provides compressive strength
- Grade M20 or higher is typical
- Steel Reinforcement: Provides tensile strength
- Main bars resist bending, distribution bars hold mains in place, and stirrups resist shear
- Construction Sequence:
- Centering/Formwork: Erection of temporary support (plywood/steel on props) to hold wet concrete in shape until it gains strength
- Reinforcement Fixing: Steel bars are placed as per structural drawings, tied together, and supported on cover blocks to maintain concrete cover
- Concrete Pouring: Concrete is placed, compacted using vibrators to remove air voids, and leveled
- Curing: The slab is kept continuously wet for a minimum of 14-28 days to achieve design strength
- Stripping/De-shuttering: Removal of formwork only after concrete gains sufficient strength (typically 7-14 days for slabs)
- Types of Slabs:
- One-way Slab: Spans and bends primarily in one direction ()
- Two-way Slab: Spans in both directions (), more efficient
- Flat Slab: Slab directly supported on columns without beams
- Waffle Slab: Grid of deep ribs for large spans
1.7 Flooring
- Definition: The permanent covering of a floor, providing a wearing surface that can support occupancy and furniture loads
- Requirements: Durable, wear-resistant, easy to clean, comfortable underfoot, and aesthetically pleasing
- Components (from bottom to top):
- Sub-grade: Compacted natural soil
- Sub-base: Layer of granular material (brickbat, gravel)
- Base Concrete (PCC): Plain cement concrete layer (1:4:8 or 1:5:10)
- Damp Proof Course (DPC): Layer of bitumen or plastic sheet
- Flooring/Finishing Layer: The top visible layer
- Common Flooring Materials:
- Concrete Flooring (Topping): Cement concrete (1:2:4) finished smooth or with a granolithic finish
- Tile Flooring: Ceramic, vitrified, or mosaic tiles laid on a cement-sand bed
- Stone Flooring: Marble, granite, or kota stone slabs
- Terrazzo: Marble chips embedded in cement matrix, ground and polished
- Wood/Parquet Flooring: Wooden blocks or strips fixed to subfloor
- Vinyl/Linoleum: Flexible sheet or tile flooring
- Skirting: A narrow vertical board or tile at the junction of wall and floor to protect the wall and cover the joint
1.8 Damp Proof Course (DPC)
- Objective: To prevent the rise of moisture from the ground into the walls and floors of a building by capillary action (rising damp)
- Causes of Dampness: Capillary rise, penetration from rain, condensation
- Ideal Characteristics of DPC Material: Impervious, durable, strong, and flexible enough to accommodate minor settlement
- Materials Used:
- Bituminous Felts (Mastic Asphalt): Most common and effective
- Plastic Sheets (Polyethylene): 0.5-1mm thick
- Metal Sheets: Lead, copper, or aluminum
- Rich Cement Concrete (1:2:4 mix): With waterproofing compound
- Bricks: Engineering bricks with low absorption
- Location of DPC:
- Horizontal DPC: Laid continuously at plinth level (150-450mm above ground level) in walls
- Also under floors (above PCC)
- Vertical DPC: Applied to the inner face of external walls in basements or earth-retaining structures
2. Building By-Laws
2.1 Introduction
- Definition: A set of legal rules and regulations enacted by municipal or local authorities to control the construction, alteration, and use of buildings within their jurisdiction
- Purpose:
- Ensure public safety, health, and general welfare
- Regulate orderly development and use of land
- Provide for adequate light, ventilation, and sanitation
- Prevent haphazard construction and urban sprawl
- Ensure structural stability and fire safety
2.2 Key Components/Provisions
- Building Line (Setback): The minimum distance that must be maintained between the building and the center line of the adjoining street/road or the boundary of the plot
- Ensures light, ventilation, and future road widening
- Floor Area Ratio (FAR) or Floor Space Index (FSI):
- Definition: The ratio of the total covered floor area of all floors to the total area of the plot
- Significance: Controls the density and volume of construction
- A higher FAR allows for taller or larger buildings
- Height Regulations: Maximum permissible height of a building, often governed by FAR, width of the road, or airport/zoning restrictions
- Open Space Requirements:
- Front, Rear, and Side Open Spaces: Minimum mandatory setbacks around the building
- Courtyards: Minimum size for interior open spaces for light and ventilation
- Parking Standards: Minimum number of car and two-wheeler parking spaces required based on building type (residential, commercial, etc.) and area
- Structural Safety: Compliance with relevant National Building Codes (e.g., Nepal National Building Code - NBC, Indian Standard IS 875 for loads, IS 1893 for earthquake design)
- Fire Safety Provisions:
- Minimum width of staircases and corridors
- Provision of fire escapes, firefighting equipment, and water storage
- Use of non-combustible materials
- Sanitation and Drainage:
- Provision of toilets, baths, and kitchens
- Requirements for septic tanks, soak pits, and connection to public sewers
- Light and Ventilation:
- Minimum window area as a percentage of floor area
- Requirements for ventilation shafts in interior rooms
- Building Use Classification: Zoning regulations specifying what activities (Residential, Commercial, Industrial, Institutional) are permitted in which areas
2.3 Process of Obtaining Building Permits
- Submission of Drawings: Architectural, structural, and service drawings along with the application form
- Scrutiny by Authority: Checking for compliance with all by-laws and codes
- Issuance of Permit: Permission to commence construction
- Stage Inspections: Inspections at foundation, plinth, completion of each floor, and final completion
- Issuance of Occupancy Certificate: Final certificate allowing occupancy after verifying all conditions are met
- Mastery of Building Technology requires both hands-on skill in execution and a thorough understanding of the governing regulations
- From the precise laying of bricks to the proper curing of concrete, and from the selection of a suitable flooring material to compliance with setback rules, every step impacts the quality, safety, and legality of the final structure
- The Building By-Laws serve as the essential framework that ensures individual construction projects contribute to a safe, healthy, and sustainable built environment for the community
Pause and recall
Without looking back, explain the main idea, recall a key definition or formula, and describe when it applies. Include assumptions and units where relevant. Revisit any step you could not explain.