Spalling concrete is concrete flaking or breaking away from a ceiling, beam or wall because the steel bars inside it have corroded, cracking and bulging the concrete that covers them. HDB attributes it largely to carbonation, a natural process that humidity speeds up. Inside an HDB flat the repair is the owner's job, with HDB co-paying half for eligible cases. In a condominium, slabs are common property for the MCST to maintain.
Everything below comes from HDB, the Ministry of National Development (MND), BCA and the Building (Strata Management) Act, linked at each point. Some of the clearest statements on HDB's repair assistance are written answers to Parliament rather than HDB web pages, so we give their dates. Where no official source publishes something, such as what a repair typically costs, we say so rather than repeat a figure from a contractor's blog.
What spalling concrete is
Reinforced concrete is steel bars cast inside concrete. The concrete over the bars, called the cover, protects them. MND, in a February 2018 written answer, defined spalling as "the flaking of concrete from the ceiling due to the corrosion of steel reinforcement bars in the concrete floor slab", and said the corrosion can lead to cracking and bulging of the concrete cover over time. It called this natural wear and tear, and generally a surface maintenance issue that regular painting of the ceiling can mitigate.
HDB's spalling concrete page puts it the same way and adds where it happens: it is a common issue for older buildings, especially in home areas with damp conditions such as kitchens and toilets. HDB also warns against leaving it. Do not delay the repair, it says, because the affected area will become larger over time, and when left unattended spalling will spread to a bigger area and weaken the building structure.
What causes it
Carbonation. HDB states that spalling is largely caused by carbonation, which it describes as a natural deterioration process. Carbonation causes the steel bars embedded in the ceiling slab to corrode, and that in turn causes the concrete cover to crack and bulge.
Moisture and acidic elements. MND's 2018 answer says the corrosion is caused by the ingress of moisture and acidic elements. Its October 2022 answer describes the same thing as the build-up of moisture and acids in the concrete over time, and advises sealing cracks and holes in the ceiling to keep moisture and oxygen out.
Humidity. HDB states plainly that a humid environment speeds up carbonation. That is why its prevention advice centres on ventilation in moisture-prone areas, and why the kitchen, toilet and bathroom ceilings are where owners tend to find it first.
Leaks and exposure. Water getting into the slab matters. BCA's Periodic Structural Inspection guidelines for structural engineers (September 2024) state that water leakage at a reinforced concrete roof will have a higher likelihood of spalling than a ceiling slab on other floors. The same guidelines ask engineers to extend their inspection where corrosion-related defects are due to exposure, to areas with high humidity or an aggressive environment, and to survey for elements such as columns immersed in water, including seawater.
Poor earlier repairs. BCA's guidelines also flag improper or incorrect repair of spalling concrete, cracks and holes, using the wrong procedure or unsuitable materials, as a reason spalling can continue to deteriorate undetected underneath fresh coats of repair.
Warning signs to look for
HDB's 2026 call for proposals on concrete spalling lists the visible signs that inspectors check for, and its own home care page adds the cracks and holes owners should watch:
- Rust stains on the ceiling or wall surface.
- Cracks, and holes in the ceiling, which HDB says should be sealed immediately.
- Bulging concrete, where the cover is being pushed out.
- Exposed reinforcement bars, where the concrete has already fallen away.
- A hollow sound when tapped, which HDB says may indicate delamination.
- Flaking or dislodged concrete on the floor below.
HDB is candid about the limits of looking. In the same call for proposals it notes that visual inspection may overlook internal voids, corrosion or delamination unless they are visible, and depends heavily on the inspector's experience, while tapping relies on skilled interpretation and is limited in hard-to-reach locations. A ceiling that looks sound is not proof that it is.
Who is responsible for the repair
The answer depends on where the spalling is and what kind of property it is in. The table sets out what each source says.
| Where the spalling is | Responsible | What the source says |
|---|---|---|
| Inside an HDB flat (ceilings, walls, beams) | Flat owner | HDB: the home owner is responsible for prevention through regular maintenance and for any repair work required. MND (2022): owners are responsible for maintaining the interior, including checking and repairing spalling concrete. |
| A new HDB flat within its first year | HDB, for defects | HDB: newly completed flats have a 1-year Defects Liability Period from key collection, during which HDB follows up on items that need rectification. |
| HDB common property: corridors, void decks, lifts and other common areas | Town Council | HDB: Town Councils control, manage, maintain and improve the common property of HDB flats, which includes corridors, void decks, lifts, water tanks, public lighting and open spaces. |
| Condominium slabs, beams, columns, external walls | Management corporation (MCST) | Building (Strata Management) Act: structural elements are common property whether or not within a lot; s.29 puts the duty to maintain common property on the MC. |
| A building facade under a PFI notice, or a building under a PSI notice | The building owner served with the notice | BCA: owners must ensure defects found are repaired. For strata developments, the MCST takes on the owner's responsibilities. |
HDB flats
HDB's position has not moved: the inside of the flat is yours to maintain, and that includes spalling. MND said so in an August 2016 answer, which named the repair of spalling concrete and ceiling leaks as the owner's, and repeated it in October 2022. HDB's spalling page goes further and lists three contractors, by area, that owners may wish to consider, with the usual caveat that the list is for reference only, is not exhaustive and is not an endorsement. You negotiate the price and scope with the contractor yourself.
Spalling often travels with a ceiling leak, and HDB's ceiling leaks page sets out a different split for that. Flat owners are responsible for their respective flats including the floor and ceiling slabs, so a leak between units is arranged and paid for jointly by you and your upstairs neighbour. A leak into a topmost-floor flat comes from the roof, which is common property the Town Council maintains. HDB adds that where a leak needs repairs to an external wall or the rooftop, the Town Council bears the full repair cost, and that for a leak affecting the void deck the Town Council and the flat owner arrange the repair together and split the cost. MND's October 2017 answer adds that where a leak is found to come from renovations in the upper flat, that owner bears the full cost of repair.
Town Council common property
On its page on the function of HDB Branches and Town Councils, HDB describes Town Councils as autonomous legal entities formed under the Town Councils Act that control, manage, maintain and improve the common property of HDB residential flats. Spalling on a common corridor ceiling, around the lifts or in the void deck is therefore one to report to your Town Council rather than fix yourself. What else the Town Council controls outside your front door is covered in the HDB renovation permit guide.
Condominiums and other strata buildings
For private strata developments the answer is in the Building (Strata Management) Act 2004. Its definition of common property in s.2(1) includes, whether or not comprised in a lot, "any structural element of the building", and the statutory examples include beams, columns, load-bearing walls and a "slab (not including any layer that is the underlayment or the flooring finishing)". Section 29(1)(b) makes it the management corporation's duty to properly maintain and keep the common property in a state of good and serviceable repair, including renewing or replacing it where reasonably necessary.
So the corroding slab above a condo unit is, on the Act's wording, the MCST's to maintain, while the finishes layered on it are a separate question. Where the two sides disagree, s.101(1) lets the Strata Titles Board settle disputes about any defect in a lot or the common property and about who bears the cost of work the MC carries out. For leaks specifically, s.101(8) presumes, unless proved otherwise, that a defect is in the lot or common property above if there is evidence of dampness, moisture or water penetration on the ceiling below. Which parts of a development are lots and which are common property is set by the strata title plan; we explain how to find it, and the other records an MCST should hold, in MCST building records and plans.
HDB's help: Goodwill Repair Assistance and HIP
Owner responsibility is not the whole story for HDB flats. Two schemes can take on some or all of the cost.
Goodwill Repair Assistance (GRA). In its October 2022 written answer, MND said that where necessary HDB assists flat owners with spalling concrete: under the GRA scheme HDB arranges the repair works and co-pays 50% of the cost for Singapore Citizen households. The owner bears the other 50%, capped at S$300 per flat. For rental flats, HDB bears the full cost of repairing spalling concrete. MND's February 2025 answer confirms the scheme is still running: requests remain high, about 80% of cases are completed within four months, and HDB prioritises cases where the spalling concrete or ceiling leak is more severe. Earlier answers describe the scheme as covering spalling and ceiling leaks due to wear and tear.
One caution. HDB's own spalling concrete page, as we read it on 9 October 2026, does not mention GRA at all and simply tells owners to engage a contractor. The scheme details above come from MND's answers to Parliament, the latest dated February 2025. Before paying a contractor, ask your HDB Branch whether your case qualifies and what the current terms are.
Home Improvement Programme (HIP). HDB's HIP page lists "repair spalling concrete/ structural cracks" as one of the Essential Improvements, which are compulsory, and states that the Government fully funds the Essential Improvements for Singapore Citizen households. HIP was introduced in 2007 for flats built up to 1986 that had not undergone the Main Upgrading Programme, and extended in August 2018 to flats built between 1987 and 1997. It proceeds only if at least 75% of a block's eligible Singapore Citizen households vote in favour. MND's 2018 answer is realistic about what it does: HIP does not stop spalling coming back or appearing elsewhere in the flat, because wear and tear continues, and for spalling after the one-year defects liability period owners can request help under GRA.
How spalling concrete is repaired
HDB says you can repair spalling in your flat yourself if the affected area is small, and sets out the method. The same sequence is what a contractor should be doing, so it is useful to know either way.
| Step | What HDB says to do |
|---|---|
| 1. Remove | Remove the spalled concrete. |
| 2. Clean the steel | Scrape and clean the exposed steel bars, and use a wire brush to remove any rust. |
| 3. Protect the steel | Apply 2 coats of anti-rust paint to the steel bars. |
| 4. Bond | Apply a bonding agent to the affected surface to ensure proper adhesion. |
| 5. Patch | Patch the hacked area using polymer modified cement mortar. |
| 6. Paint | Paint over the patched area to match the rest of the ceiling. |
If the area is large, HDB says to engage a contractor to repair the ceiling promptly, before more concrete dislodges and potentially causes injury. While you wait, it advises removing any loose concrete yourself, safely: wear a helmet, gloves and eyewear, use a hammer and chisel or a long flat screwdriver, protect the floor with thick cardboard, secure the ladder, hold the loose piece and bring it down carefully, and dispose of the debris at the centralised bin collection chute at the ground level of your block.
Prevention, in HDB's words, comes down to three habits: paint ceilings regularly, because paint protects the ceiling and helps to prevent carbonation; seal cracks and holes properly, including holes left after removing a ceiling fixture; and ensure sufficient ventilation, opening windows, vents or doors in the kitchen, toilet and bathroom when they are not in use.
Large-scale and structural repairs are another matter. BCA's PSI guidelines state that major repairs and strengthening work are to be treated as building works, which brings in the approval procedures for building plans and permits. That is the professional engineer's territory, not a patch-and-paint job.
Where BCA's periodic inspections come in
For whole buildings, spalling is one of the things Singapore's two periodic inspection regimes under the Building Control Act are designed to catch. MND's 2022 answer links them directly to spalling in HDB blocks.
Periodic Structural Inspection (PSI). BCA's PSI page sets the cycle at once every 10 years for residential buildings and once every 5 years for non-residential ones, and says that when defects are identified they must be repaired. MND (2022) said these inspections include checking units for spalling concrete and structural cracks, and that for flats completed before 1 January 1989 HDB goes beyond PSI and inspects at 5-yearly intervals. BCA's guidelines for structural engineers list spalling concrete and corrosion of steel among the signs of deterioration to record, ask the engineer to comment on their extent, possible causes and seriousness, and to grade each as a defect of no structural significance, one requiring remedial action or monitoring, or a suspected defect of structural significance requiring full investigation and immediate action. Where spalling is observed, the engineer should carry out simple tests such as tapping in other areas, and where it reflects degradation due to age, inspection coverage should generally be increased across the building. The full regime is in our Periodic Structural Inspection guide.
Periodic Facade Inspection (PFI). BCA's Guidelines on Periodic Facade Inspection (version 1.3, September 2026) list "spalling/ delamination/ cracking of concrete" among the common facade defects, and spalling concrete appears in the checklist of defects the competent person must report on. Each facade type is classified as Safe, Require Repair or Unsafe. If it is Require Repair or Unsafe, the competent person must recommend immediate measures so the facade does not endanger anyone, loose or dangling elements must be removed immediately, and where the defects involve structural elements the competent person is advised to engage a civil or structural professional engineer. The guidelines also name failed anchors due to spalling concrete among the common causes of exterior false ceiling panels falling. PFI applies to buildings over 20 years old and more than 13 metres high, every 7 years; the details are in our Periodic Facade Inspection guide.
Recording the extent before it is repaired
Volumet is a 3D scanning and survey company. We are not professional engineers, we do not certify structural safety, and we do not carry out or sign PSI or PFI inspections. Diagnosis, grading and the repair specification belong to the structural engineer or competent person, and the repair belongs to the contractor.
What we can do is make the record those people work from. A laser scan of a car park, corridor, roof or plant room captures every visible surface, so each patch of spalling, bulge, rust stain or crack can be located on a measured plan and its area taken off, rather than described as "several spots on level 3". Drone imagery and scanning do the same for elevations. A record made before the repair can be compared with the next one, which helps an MCST or Town Council see whether spalling is spreading or coming back. These sit within our support for periodic structural inspections and facade inspections.
The limit matters as much as the capability. A scan records what is visible and measurable. It does not hear a hollow ceiling or see corrosion behind sound-looking concrete, which is why tapping, close-range inspection and the engineer's judgement stay where BCA puts them. For a single HDB ceiling, you do not need us at all: follow HDB's steps or call a contractor.
Rule of thumb: small and inside your flat, repair it or ask your HDB Branch about GRA. In a corridor or void deck, tell the Town Council. In a condo, tell the MCST. Across a whole building, it is a job for the engineer.