Spalling Concrete & Exposed Rebar in Ghana — Causes & Fix

Q: What is spalling concrete?

Spalling is when concrete cracks and breaks away from the surface, usually because the steel reinforcement (rebar) inside has rusted, expanded, and pushed the surrounding concrete apart from within. It shows up as flaking, bulging, or chunks of concrete falling away, often exposing rusted rebar underneath.

Q: Can you just paint over spalling concrete with waterproofing coating?

No. Coating over spalled concrete without treating the exposed rebar and repairing the concrete first traps moisture against active rust and speeds up failure. The rebar has to be exposed fully, cleaned, treated, and the concrete patched before any waterproofing membrane goes on.

Q: What causes spalling concrete in Ghana specifically?

Water penetrating unwaterproofed roofs, parapets or walls reaches the rebar over time. In coastal areas within 15km of the sea, airborne chloride accelerates corrosion significantly, which is why spalling appears faster and more aggressively in Accra, Tema and Takoradi than inland towns.

Q: How much does spalling concrete repair cost in Ghana?

Concrete crack injection and patch repair is priced per project based on the extent of damage and rebar exposure. Waterproofing the repaired area afterward follows standard rates of GHS 80-280 per square metre depending on whether fleece reinforcement is needed.

October 1, 2026

Spalling concrete — flaking, bulging, or chunks breaking away to expose rusted rebar — means water has been reaching your steel reinforcement for a long time. It cannot be fixed by coating over it. The rebar must be exposed, cleaned of rust, treated, and the concrete patched before any waterproofing membrane is applied, or the coating simply traps active corrosion underneath.

What's Actually Happening Inside the Concrete

Reinforced concrete works because embedded steel rebar gives it tensile strength the concrete alone lacks. That steel is protected from rusting by the concrete's natural alkalinity — as long as water and carbon dioxide don't reach it. When an unwaterproofed roof, parapet, or wall lets water in over months or years, two things happen: the concrete carbonates, losing the alkalinity that protects the steel, and the rebar starts to rust. Rust occupies roughly six to ten times the volume of the original steel, so as it forms, it physically pushes outward, cracking and eventually blowing off the concrete cover above it. That's spalling — it's a symptom of a much older water problem, not a standalone defect.

Why Ghana's Coast Makes It Worse

Anywhere within about 15km of Ghana's coastline — Accra, Tema, Takoradi, Winneba, Cape Coast — airborne salt (chloride) accelerates rebar corrosion significantly compared with inland towns. Chloride ions penetrate concrete and attack the steel directly, bypassing the slower carbonation process. This is why coastal buildings often show spalling years before an equivalent inland building would, and why coastal-rated primers and chloride-blocking treatments matter more there than anywhere else in the country.

The Correct Repair Sequence

Step	What Happens
1. Break out	Remove all loose and hollow-sounding concrete around the affected area, not just the visibly broken part.
2. Expose rebar fully	Clear concrete back until sound steel is fully visible — partial exposure leaves hidden corrosion.
3. Clean and treat steel	Remove rust mechanically, apply a rust-inhibiting primer to the exposed rebar.
4. Patch repair	Rebuild the concrete profile with a bonding agent and repair mortar.
5. Waterproof	Apply a 2-coat polyurethane membrane (fleece-reinforced if the area is cracked or has moving joints) over the repaired, cured surface.

Why Waterproofing Alone Isn't a Fix Here

Coating directly over spalled or hollow concrete without repairing it first does more harm than good. Moisture already trapped near the rebar stays trapped, active rust continues to expand, and the new coating will crack and lift as the repair-free concrete keeps failing underneath it. Any contractor who offers to \"just coat it\" over visible spalling without discussing rebar exposure and patch repair is skipping the part of the job that actually matters.

Related Work

We've carried out structural patch repair alongside waterproofing on a crack injection project, and applied coastal-rated systems on a sea-facing home in coastal Ghana where chloride exposure was the root cause.

Frequently Asked Questions

What is spalling concrete?

Concrete cracking and breaking away because rusted rebar inside has expanded and pushed it apart, often exposing the steel.

Can you just paint over spalling concrete with waterproofing coating?

No. The rebar must be exposed, cleaned, treated, and the concrete patched first, or the coating traps active corrosion underneath.

What causes spalling concrete in Ghana specifically?

Long-term water penetration reaching the rebar; accelerated near the coast by airborne chloride within about 15km of the sea.

How much does spalling concrete repair cost in Ghana?

Priced per project based on the extent of damage; waterproofing the repaired area afterward follows the standard GHS 80-280/m² range.

Related Resources

Seeing cracked or bulging concrete on your building? Book an inspection or call 0555 548 001.

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