Case Study: FLOOR SCREEDING FAILURE LEADING TO TILE DEBONDING/UNEVEN FLOORING

Project : Commercial office fit-out – Level 3 & Level 4 flooring works

Problem Observed After installation of floor finishes, multiple defects were reported: - Hollow-sounding floor tiles - Localized tile debonding - Noticeable floor unevenness (lippage and “ponding” effect in some areas) - Cracks reflecting through tiles along screed joints Affected area: ~120 m² Measured surface unevenness: up to 8–12 mm deviation over 2 m straightedge (exceeding tolerance of ~3–5 mm) 1) Site Measurements and Findings - Screed Quality - Screed thickness: 25 mm to 55 mm (non-uniform) - Compressive strength test: 18–22 MPa (acceptable, but inconsistent zones) - Moisture content at tiling stage: 9–11% (too high for installation) - Surface flatness: failed straightedge test in multiple zones 2) Observations - Visible segregation in screed mix (cement-rich and weak zones) - Hairline shrinkage cracks present before tiling - Uneven curing (some areas dry, others still damp) - No consistent use of screed leveling guides or screed rails 3) Root Cause Analysis Immediate Causes - Uneven screed application thickness - Premature tiling before screed fully cured - Poor surface finishing (trowel marks, laitance not removed) Contributing Causes - Inadequate leveling control during screeding works - No moisture testing prior to tile installation - Lack of screed curing protection (rapid drying in some areas) - Absence of bonding primer between screed and tile adhesive 4) Root Cause Failure in screed quality control and curing management, leading to an unstable and uneven substrate that directly compromised tile adhesion and finish quality. 5) Corrective Action (Simple and Practical) Immediate Rectification - Remove affected tiles and weak screed sections - Patch repair or rescreed low-strength/cracked areas - Mechanical grinding to achieve uniform level surface - Apply bonding primer before retiling - Reinstall tiles using proper adhesive bed with ≥80% coverage Simple Preventive Measures - Enforce screed level tolerance checks using 2 m straightedge - Require minimum curing period (7–14 days depending on thickness) - Conduct moisture content test before tiling starts - Use screed guide rails or laser leveling for better control - Mandatory consultant inspection before tile installation Lessons Floor screeding is often underestimated, but it is the foundation of all floor finishes. Even high-quality tiles and adhesives cannot perform properly if the screed is uneven, weak, or installed under poor curing conditions. Most failures in floor finishing systems originate not from the finish itself, but from the substrate below it.