Slab Load Test
(Floor Slab Load Test)

Static load test on RCC floor slabs to verify their structural adequacy under design loads — mandatory for post-tensioned slabs, transfer plates and slabs with unusual loading or construction deficiencies.

Overview

What is the Slab Load Test?

The Slab Load Test applies a uniformly distributed or concentrated static load to an RCC floor slab while measuring deflections at mid-span and supports. The test verifies that the slab can sustain design loads with acceptable deflections and recovers elastically upon load removal.

Conducted as per IS 456 Clause 17.6 and ACI 318, slab load tests are specified when there is doubt about construction quality, when cube test results are below acceptance criteria or for commissioning of critical transfer slabs, prestressed flat plates and industrial floor slabs. Global Lab conducts slab load tests using water load, kentledge or precast blocks.

IS 456 Compliance Test

Mandatory test per IS 456 Cl. 17.6 when construction quality is in doubt.

Uniform Load Application

Water load or precast blocks provide accurate uniform pressure on slab.

24-Hour Load Hold

IS 456 requires load sustained for 24 hours — creep and sustained load effects captured.

Elastic Recovery Verification

IS 456 acceptance: 75% deflection recovery within 24 hours after load removal.

NABL Certified Reports

All results issued on NABL-accredited letterhead per IS 456/ACI 318.

All Slab Types

RCC, prestressed, flat plate, waffle and post-tensioned slabs tested.

Test in Action

Slab Load Test — Site Images

Load Applied on Slab

LVDT Deflection Measurement at Mid-Span

24-Hour Load Hold Monitoring

Test Procedure

How the Slab Load Test is Conducted

1

Deflection Gauge Installation

Dial gauges and LVDTs are installed at mid-span, quarter-span and support locations on the underside of the slab.
2

Zero Reading

Initial zero readings taken before any test load is applied.
3

Load Application

Test load (1.25 DL + 1.5 LL per IS 456) is applied uniformly in stages using water tanks, precast blocks or kentledge over 3 hours.
4

24-Hour Sustained Load Reading

Deflection is recorded at full test load and monitored for 24 hours to capture creep.
5

Load Removal & Recovery

Test load removed. Deflection recovery monitored for 24 hours. Pass criterion: 75% recovery per IS 456 Cl. 17.6. NABL report within 3 days.

Standards & Specifications

Applicable Test Standards

Standard	Title	Scope	Type
IS 456:2000 Cl. 17.6	Plain and Reinforced Concrete — Load Testing of Flexural Members	Slab Load Test	Indian Standard
ACI 318	Building Code Requirements for Structural Concrete — Load Testing	Structural Testing	ACI
IS 1905	Code of Practice for Structural Use of Unreinforced Masonry	Masonry	Indian Standard
IS 875	Code of Practice for Design Loads — Live Loads	Design Loads	Indian Standard

Applications

Where is the CAPO Test Used?

Slabs with cube test results below IS 456 acceptance criteria

Post-tensioned flat plates and transfer slabs after construction

Industrial floor slabs before commissioning for heavy machinery or racking

Slabs affected by premature formwork removal or construction incidents

Slabs with visible cracking, excessive deflection or honeycombing

Commissioning of long-span prestressed slabs in commercial buildings

Why Choose Global Lab

Our Advantages

NABL Accredited ReportsIS 456 and ACI 318 compliant certificates accepted by all structural consultants.

Multiple Load MethodsWater load, precast blocks and kentledge options based on site accessibility.

Autovity Digital Reports24-hour deflection records and recovery curves accessible digitally.

Structural Engineering ExpertiseOur engineers interpret results and provide written pass/fail recommendation.

Pan-India CoverageTeams across 7 lab locations for rapid mobilisation.

Combined TestingSlab load test combined with core strength test and UPV for full slab assessment.

Slab Load Test(Floor Slab Load Test)