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IS 10505 : 1983Code of practice for construction of floors and roofs using precast concrete waffle units

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ACI 318 · EN 1992-1-1 · EN 13369
CurrentSpecializedCode of PracticeBIMStructural Engineering · Planning, Housing and Pre-fabricated Construction
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OverviewValues7InternationalTablesFAQ4Related

IS 10505:1983 is the Indian Standard (BIS) for construction of floors and roofs using precast concrete waffle units. This code provides guidelines for the design, manufacture, and construction of floors and roofs using precast concrete waffle units. It covers materials, dimensions, design considerations for composite action, manufacturing processes like moulding and curing, and on-site erection procedures.

Code of practice for construction of floors and roofs using precast concrete waffle units

Overview

Status
Current
Usage level
Specialized
Domain
Structural Engineering — Planning, Housing and Pre-fabricated Construction
Type
Code of Practice
International equivalents
ACI 318-19 · American Concrete Institute (ACI), USAEN 1992-1-1:2004 · European Committee for Standardization (CEN), EuropeEN 13369:2018 · European Committee for Standardization (CEN), EuropePCI MNL 120-17 · Precast/Prestressed Concrete Institute (PCI), USA
Typically used with
IS 456IS 269IS 383IS 1786IS 432IS 2502
Also on InfraLens for IS 10505
7Key values1Tables4FAQs

BIM-relevant code. See the BIM Hub for ISO 19650, IFC, and LOD/LOIN frameworks used alongside it.

Practical Notes
! Strict adherence to dimensional tolerances in Table 1 is critical for proper fit-up during erection.
! Ensure proper surface preparation of precast units before placing in-situ concrete to achieve monolithic composite action.
! Careful handling and stacking of the precast units are essential to avoid damage before installation.
Frequently referenced clauses
Cl. 3MaterialsCl. 4Waffle Units (Dimensions and Reinforcement)Cl. 5DesignCl. 7ManufactureCl. 9Erection and Construction
Pulled from IS 10505:1983. Browse the full clause & table index below in Tables & Referenced Sections.
precast concretewaffle unitsconcretesteel reinforcement

International Equivalents

Similar International Standards
ACI 318-19American Concrete Institute (ACI), USA
MediumCurrent
Building Code Requirements for Structural Concrete and Commentary
Covers design principles for two-way joist systems (waffle slabs) within the main concrete code.
EN 1992-1-1:2004European Committee for Standardization (CEN), Europe
MediumCurrent
Eurocode 2: Design of concrete structures - Part 1-1: General rules and rules for buildings
Provides design rules for ribbed and waffle slabs as an integrated part of the general concrete design standard.
EN 13369:2018European Committee for Standardization (CEN), Europe
HighCurrent
Common rules for precast concrete products
Addresses manufacturing, testing, and quality control of precast elements, similar to the precasting aspects of IS 10505.
PCI MNL 120-17Precast/Prestressed Concrete Institute (PCI), USA
HighCurrent
PCI Design Handbook: Precast and Prestressed Concrete
Functions as a practical 'code of practice' with extensive design aids and construction details for precast systems.
Key Differences
≠IS 10505 is a prescriptive 'Code of Practice' from 1983, while modern standards like ACI 318 and Eurocode 2 are performance-based design codes focusing on achieving limit states.
≠The Indian standard is based on older design philosophies (Working Stress Method or early Limit State Method of IS 456:1978), whereas current international codes exclusively use more advanced Limit State Design (or Strength Design) with different partial safety factors.
≠IS 10505 contains minimal to no specific guidance on seismic design and detailing, which is a major mandatory component of modern codes like ACI 318 and Eurocode 8 (used with Eurocode 2).
≠Modern international codes cover a much wider range of concrete strengths (e.g., up to 90 MPa in Eurocode 2) and have more stringent durability-based requirements compared to the M15/M20 grades mentioned in IS 10505.
≠IS 10505 is a standalone document for a specific product type, whereas ACI 318 and Eurocode 2 integrate the design of waffle slabs directly into the main concrete code as a type of two-way slab system.
Key Similarities
≈The fundamental structural concept of a two-way grid of ribs (joists) with a thin top slab to create a lightweight, stiff flooring/roofing system is identical across all standards.
≈All codes recognize the monolithic action between the precast units (or in-situ forms) and the cast-in-place topping slab for the composite section's strength and stiffness.
≈The requirement to check for primary failure modes, including flexure in ribs, shear at supports, and punching shear at columns, is a common principle in both IS 10505 and its international counterparts.
≈All standards mandate checks for serviceability limit states, specifically deflection control and crack width control, to ensure the floor or roof performs adequately under service loads.
Parameter Comparison
ParameterIS ValueInternationalSource
Minimum Concrete Grade (for units)M15 (≈15 MPa cube strength)2500 psi (≈17 MPa cylinder strength / 21 MPa cube strength)ACI 318-19
Minimum Topping Slab Thickness25 mmGreater of 50 mm (2 in.) or 1/12 of clear spacing between ribsACI 318-19
Maximum Rib Spacing750 mm (centre-to-centre)762 mm / 30 in. (clear spacing between ribs)ACI 318-19
Minimum Rib Width (at bottom)65 mm100 mm (4 in.)ACI 318-19
Minimum Concrete Cover (mild exposure)15 mm for reinforcement20 mm (3/4 in.) for slabs/joists (non-prestressed)ACI 318-19
Shear Strength EnhancementShear stress may be increased by 10% for tapered ribsConcrete shear capacity (Vc) may be taken as 1.1 times the standard value for joistsACI 318-19
⚠ Verify details from original standards before use

Key Values7

Quick Reference Values
Minimum grade of concrete for precast unitsM15
Minimum grade of concrete for in-situ structural concreteM15
Minimum thickness of structural in-situ topping30 mm
Standard width of the rib of waffle unit75 mm
Typical standard overall depth of waffle units100, 125, 150, 175, 200 mm
Permissible tolerance in length of waffle unit± 6 mm
Permissible tolerance in overall depth of waffle unit± 3 mm

Tables & Referenced Sections

Key Tables
Table 1 - Permissible Deviations in the Dimensions of Waffle Units
Key Clauses
Clause 3 - Materials
Clause 4 - Waffle Units (Dimensions and Reinforcement)
Clause 5 - Design
Clause 7 - Manufacture
Clause 9 - Erection and Construction

Related Resources on InfraLens

Cross-Referenced Codes
IS 456:2000Plain and Reinforced Concrete - Code of Pract...
→
IS 269:2015Ordinary Portland Cement - Specification
→
IS 383:2016Coarse and Fine Aggregates for Concrete - Spe...
→
IS 1786:2008High Strength Deformed Steel Bars and Wires f...
→
IS 432:1982Mild Steel and Medium Tensile Steel Bars and ...
→
IS 2502:1969Code of Practice for Bending and Fixing of Ba...
→

Frequently Asked Questions4

What is the minimum grade of concrete for precast waffle units?+
M15 (as per Clause 3.1.1).
What is the minimum thickness for the cast-in-situ structural topping?+
30 mm (as per Clause 9.5.1).
What is the permissible manufacturing tolerance for the length of a waffle unit?+
± 6 mm (as per Table 1).
Does this code provide detailed design calculations?+
No, it outlines design principles and refers to IS 456 for detailed design of the composite section.

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