Before and after spalling concrete repair on a Singapore HDB ceiling

Spalling concrete contractor

Flaking concrete and brown rust stains on a ceiling mean the steel bars inside the slab have started to corrode. Rust takes up more room than steel and keeps pushing the concrete apart. Each wet season makes it worse.

Roof Doctors is a spalling concrete contractor for HDB flats and private homes across Singapore, and we repair commercial and industrial concrete too. We trace the cause and treat the steel, then rebuild the concrete with repair mortar. On structural concrete our crews work in line with BCA guidelines. Every job starts with a free inspection and comes with a workmanship warranty.

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Free first inspectionBizSafe and BCA-registeredWorkmanship warranty

Spalling, crack or honeycomb

Spalling, crack or honeycomb? How to tell them apart

All three look like damaged concrete, but each has its own cause and its own repair. Patch the wrong problem and the damage returns around the edge of the patch.

Type	What you see	Usual cause	Typical repair
Spalling	Flaking or falling concrete, rust stains, exposed steel bars	Corroding rebar pushing the concrete cover off	Hack back, treat the rebar, patch with repair mortar
Cracks	Hairline or wider cracks in slabs, beams, walls or floors	Shrinkage, settlement, overload or structural movement	Seal or inject the crack, and strengthen it if the crack is structural
Honeycomb	Rough voids with exposed stones on the surface	Poor compaction when the concrete was poured	Clean out loose material and fill with grout or repair mortar

Exposed rusty rebar in a spalling concrete ceiling in a Singapore HDB flat

Concrete spalling

Spalling is the most urgent of the three. Once the rebar is exposed, corrosion speeds up and loose pieces can fall.

Ceiling vs floor spalling ›

Concrete cracks

Most cracks come from shrinkage and only need sealing. A crack that keeps widening needs a structural check first.

Crack injection ›

Concrete floor damage

Floors crack under load and wear at the surface. They also spall where steel or pipes underneath have corroded.

Concrete floor repairs ›

Root causes

Root causes and the repair that matches

We repair the damage and deal with whatever caused it. Leave the cause in place and the spalling or cracking comes back.

Root cause	What happens	Our solution
Carbonation	Carbon dioxide from the air slowly lowers the alkalinity of the concrete cover, and the steel loses its natural protection	Repair mortar plus an anti-carbonation coating
Rebar corrosion	Water and oxygen reach the steel through cracks or thin cover, and the steel rusts and expands	Remove the rust, apply a corrosion inhibitor and rebuild the cover
Chloride attack	Salts from sea air or contaminated materials break down the protective layer around the steel	Remove the contaminated concrete, treat the steel and rebuild
Structural movement	Settlement, overload or vibration opens cracks that keep moving	Structural strengthening first, then crack injection
Poor workmanship	Thin cover, poor compaction or the wrong mix during construction	Hack out the defective concrete and redo it to specification

HDB ceiling spalling

HDB ceiling spalling concrete repair

Spalling concrete is one of the most common defects in older HDB flats, and it usually starts in the bathroom or kitchen ceiling. Moisture from the wet areas soaks into the slab, and the steel bars rust and swell until the concrete cover cracks off. It starts as a bulge or crack in the ceiling paint. Brown rust lines follow, then loose chunks of concrete.

A skim coat of plaster hides the damage for a few months. Underneath, the rust keeps spreading until the patch drops off. A lasting repair deals with the steel:

Hack off loose concrete back to sound concrete, around and behind the corroded bars
Wire-brush the rust off the bars
Coat the bars with an anti-corrosion primer
Apply a bonding agent so the new mortar grips the old concrete
Rebuild the slab in layers with polymer-modified repair mortar
Skim, seal and repaint so the ceiling matches the rest of the room

Who pays depends on your flat and on HDB’s current policy. Our guide to HDB and BTO spalling concrete explains what owners need to know, and ceiling vs floor spalling concrete covers why the two need different fixes.

HDB ceiling spalling concrete showing flaking surface and exposed rusted rebar

Contractor treating exposed rebar with anti-corrosion primer during HDB spalling concrete repair

How long does concrete repair take?

A small ceiling repair often takes a day or two. That includes the time the mortar needs to cure before the final coat of paint. Larger areas, beams and floors take longer.

Your quote states the timeline. In HDB flats we schedule the hacking within the hours HDB allows for noisy renovation works.

Keeping spalling from coming back

Spalling returns when moisture keeps reaching the steel. Our wall leakage repair and grouting teams can stop the water at its source. At home, these habits keep the slab dry:

Fix any leak from the unit above or the bathroom floor before it soaks the slab again
Keep the bathroom ventilated so steam does not sit on the ceiling
Use a moisture-resistant ceiling paint and repaint when it starts to peel
Check repaired areas once a year for new cracks or rust spots

Floors

Concrete floor repairs

Floors take a different kind of wear. Car porches, factory floors and warehouse slabs crack under load and wear away at the surface. Some also lift where the steel or pipes underneath have corroded.

Our crew repairs cracked and spalled floor slabs and fills honeycombed areas. Worn floors get a polymer-modified screed that leaves the surface level and safe to use again.

Crack injection for floor slabs
Patch repair of spalled areas and exposed rebar
Resurfacing and levelling with repair screed
Joint repair in car porches and driveways

Choosing a spalling concrete contractor

A cheap patch and a proper repair look the same for the first few months. Before you hire any spalling concrete contractor, ask how they will treat the rebar, which repair mortar they use and what the warranty covers. If the plan is to skim and paint, expect the damage back.

Working to BCA guidelines

Where a repair touches structural concrete, we work in line with BCA guidelines for concrete repair. If the damage looks structural, such as a crack that keeps widening or a heavily corroded beam, we will tell you it needs an engineer’s assessment before any patching starts.

Spalling caused by a long-running leak also needs the leak fixed. We check for ceiling leakage above the slab at the same time.

Why choose Roof Doctors

Why Roof Doctors

Specialist waterproofing and roofing contractor, 15+ years in Singapore
Free inspection and written quote, no obligation
BizSafe and BCA-registered (ROC 201132164H)
Workmanship warranty on every job
Rebar treated on every spalling repair

Coverage

HDB, condo and landed homes
Commercial and industrial
Singapore-wide

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FAQ

Frequently asked questions

Q. Is ceiling spalling dangerous?

Small spalling looks cosmetic at first, but it shows the steel inside the slab is corroding. Left alone, the slab weakens and pieces of concrete can fall. Fix it early, while the repair is small.

Q. How much does HDB ceiling spalling repair cost?

It depends on the size of the damaged area and how deep the corrosion goes. WhatsApp us a photo for a quick estimate, or book a free inspection for a fixed quote.

Q. How long does the repair last?

A repair that treats the steel before patching is a long-term fix, and it comes with a workmanship warranty. A skim coat over rusting steel usually fails within months.

Q. Can I just paint over spalling concrete?

No. Paint traps moisture against the slab and the rust keeps spreading underneath. We treat the steel first.

Q. Do you do concrete floor repairs as well as ceilings?

We do. Our crews repair cracked, spalled and worn concrete floors in homes, car porches, factories and warehouses.

Q. Is your work BCA-compliant?

Where structural concrete is involved, we work to BCA guidelines for concrete repair.