Spalling Repair

Spalling Repair

Concrete repair · Registered Minor Works Contractor Class II

D-8 Limited spalling repair: remove loose concrete to expose reinforcement

Understanding Concrete Spalling and Its Risks

Concrete spalling appears as cracks, bulging, crumbling or falling chunks that expose rusted reinforcement. The most common cause is water ingress that rusts steel bars; rust expands about two to three times in volume and bursts the concrete from within. Carbonation and leakage from upper floors or external walls accelerate the process.

Falling ceiling concrete can injure occupants; external-wall spalling endangers pedestrians and vehicles, and owners may face legal liability. Ongoing corrosion also weakens structural capacity. Repair must follow proper procedures—not a thin plaster cover.

Ceiling plaster cracking and large-area peeling
Ceiling plaster cracking, bulging and sheet peeling
Ceiling concrete spalling with substrate exposed
Ceiling concrete fallen with substrate exposed
External canopy concrete cracking and spalling
External canopy cracking, risking pedestrians and vehicles

Proper Repair Process

  1. Step 1: remove loose concrete and expose reinforcement
    Step 1 Cut and remove all loose concrete until a sound substrate is exposed.
  2. Step 2: expose rusted reinforcement after cutting
    Step 2 Descale rusted reinforcement and apply Sika primer for corrosion protection and bonding.
  3. Step 3: fill with professional repair mortar
    Step 3 Fill with professional repair mortar—not ordinary cement sand.
  4. Step 4: repaint after curing
    Step 4 After curing, repaint the finished surface.

If leakage is not stopped before repair, spalling may return within years. Structural or external-wall works should use a qualified registered contractor; severe reinforcement corrosion needs professional assessment for strengthening or replacement.

Common Professional Materials

Fosroc Renderoc HB40 repair mortar Fosroc RenderocFosroc
Sika repair mortar and primer Sika Hong KongSika Hong Kong
OptimixOptimix

Case Highlights

Indoor ceiling spalling repair with temporary structural propping

Indoor Ceiling Spalling

Large-area ceiling spalling caused by leakage. Stop the water source first, then remove loose concrete, treat rust and repair with professional mortar.

Temporary propping of ceiling and walls during structural repair

Temporary Support & Compliant Works

Structural repairs require temporary propping and must be handled by a Registered Minor Works Contractor (Class II) using proper procedures—not plaster cover alone.

URA Building Maintenance Grant Scheme for Needy Persons

The Urban Renewal Authority supports eligible owners with grants of up to HK$80,000 per property / eligible applicant. Covered works may include repairing loose, cracked or spalled concrete, external plaster, defective windows/doors, waterproofing and pipes. Eligibility and income/asset limits follow the latest URA rules.

We can help assess the works scope and keep before/during/after photos and invoices for eligible owners to apply. URA hotline: 3188 1188.

Class II Licence

Registered Minor Works Contractor (Class II)

Cause Assessment

Identify leakage, carbonation or reinforcement corrosion sources first

Proper Repair

Professional repair mortar—not plaster cover alone

Compliant Construction

Handle external-wall and structural repairs under the minor works control system

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