1.3 Building Technology
1.3 Building Technology
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)
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 (Ly/Lx>2)
Two-way Slab: Spans in both directions (Ly/Lx≤2), 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
FAR=Plot AreaTotal Covered Floor Area
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
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