Swollen under-sink cabinets: rebuild the carcass, do not hack the kitchen
A swollen under-sink cabinet in Singapore is usually a slow waste leak. A sectional rebuild is S$280 to S$700 and takes 3 to 5 hours with no HDB hacking permit. A full kitchen is S$5,000 to S$6,500. This guide shows which panel to change, which board survives the next drip, and when the weep hole or gas riser means you must stop.
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Executive summary and why it fails
A swollen under-sink cabinet in Singapore is usually a slow waste leak. A sectional rebuild is S$280 to S$700 and takes 3 to 5 hours with no HDB hacking permit. A full kitchen is S$5,000 to S$6,500. This guide shows which panel to change, which board survives the next drip, and when the weep hole or gas riser means you must stop.
Particle board under a Singapore sink is a sponge with a melamine face. A bottle trap, a dishwasher drain hose or a weeping tap tail can drip for weeks before the door looks wrong. The base goes soft, then the side gable, then the toe-kick. Homeowners ask for a new kitchen because the doors still match the rest of the flat and a contractor has said the box is finished. The doors are often the only part that is not finished. The structural panels are the part that holds water.
Moisture-resistant plywood, PVC foam board, honeycomb aluminium and stainless steel do not fail the same way. Plywood holds a screw and can be edge-banded to match, but it swells again if the leak is not stopped. PVC foam does not swell and is the usual conversion when a dishwasher hose has already destroyed one base. Honeycomb aluminium is light and stable, and it needs the right rivet or screw because a wood screw in a thin skin spins. Stainless is the heavy option under a commercial-style sink. Density and screw-holding decide the choice, not the colour of the door.
Two HDB details decide whether the repair is still legal a year later. The kitchen or service-yard weep hole has to stay open so a flood can leave the flat instead of soaking the neighbour. The City Energy gas-riser inspection panel cannot be covered by a new gable or a new plinth. A sectional repair does not change the layout, so it does not need a renovation permit. Replacing the whole kitchen, moving the sink, or boxing in the riser is a different job.
Homey Furnishing Pte. Ltd. (ACRA UEN 202018148K), 27 Mandai Estate, #06-10 Innovation Place, Singapore 729931, carries the permit-exempt portion of this work. V On Construction Pte. Ltd. (ACRA UEN 201611708H), listed on the HDB Directory of Renovation Contractors, carries any scope that needs an HDB renovation permit. Those two invoices are not interchangeable. Waste and bottle-trap repairs on the existing point are PUB Simple Plumbing Works. A new supply pipe from the riser is a PUB Licensed Plumber. Covering a gas riser is a City Energy problem, not a carpentry preference.
Ten-minute diagnostic: safe check versus stop
Spend ten minutes with a torch, your phone camera, and a tape before you buy a product or book a hack. Write down what you see. The safe checks below do not ask you to open a live wire, cut a pressurised pipe, or lean out of a window. Press a thumb into the base at the trap. If the face dents or smells sweet, the board is wet inside. Open the doors and photograph the weep hole and any gas-riser grille before a panel is designed to cover them.
Stop at the red-flag column. Stop if water is still dripping, if you can see the gas riser and the new side would cover it, or if the stone top is unsupported once the base is cut out. The reason DIY fails is almost never a lack of effort. It is that the tool or chemical makes the next professional repair harder, or it hides a leak, a live conductor, or a deposit line until the damage is larger than S$280 to S$900 for a sectional rebuild or waterproof conversion.
| Symptom or measurement | Safe DIY check | Red flag: stop | Why DIY fails |
|---|---|---|---|
| Base dents under the trap | Press with a thumb and photograph. Do not cut the board out. | Water is still dripping, or the stone top would be left unsupported | A new panel over a live leak swells again within months |
| Sweet smell and a soft toe-kick | Look with a torch and confirm the weep hole is still open | The new gable would cover the City Energy gas riser | A covered riser fails the next inspection even if the cabinet looks neat |
| Doors still match the kitchen | Open them and check only the base and the gable | A full-kitchen quote is being accepted from the door faces alone | The doors are often the only sound part of the box |
| Dishwasher hose is wet at the clamp | Dry it and see if the drip returns in an hour | You cut or extend a supply pipe | A new supply point is a PUB Licensed Plumber, not a cabinet screw |
Professional on-site sequence
This is the sequence a careful technician uses so you can tell a shortcut from a finished job. Tools stay in the van. Readings and photos go on the same worksheet as the price. The usual kit is a moisture meter, a multi-tool, clamps, moisture-resistant plywood or PVC foam, exterior glue, edge band, and a new trap washer. The stone top is propped before any base is cut.
- Step 1. Make the area safe and confirm the symptom still matches the photos. For Swollen under-sink cabinets: rebuild the carcass, do not hack the kitchen, that means Stop if water is still dripping, if you can see the gas riser and the new side would cover it, or if the stone top is unsupported once the base is cut out.
- Step 2. Measure before touching the finished surface. Press a thumb into the base at the trap. If the face dents or smells sweet, the board is wet inside. Open the doors and photograph the weep hole and any gas-riser grille before a panel is designed to cover them.
- Step 3. Set protection and lay out the tools that belong to this material. The usual kit is a moisture meter, a multi-tool, clamps, moisture-resistant plywood or PVC foam, exterior glue, edge band, and a new trap washer. The stone top is propped before any base is cut.
- Step 4. Carry out the repair in the order the material allows. the new board is fixed over a live drip, or a gable covers the gas riser or the weep hole is the failure this order is written to avoid.
- Step 5. Test in place. The trap is filled and watched for ten minutes. The weep hole is visible. The gas-riser panel, if there is one, still opens. Moisture in the new base reads in the dry range.
- Step 6. Clean, label the photographs against the invoice lines, and leave the statutory openings, weep holes, access panels and labels visible.
The order matters because the new board is fixed over a live drip, or a gable covers the gas riser or the weep hole is what happens when a step is rushed. Handover is a measurement, not a handshake. The trap is filled and watched for ten minutes. The weep hole is visible. The gas-riser panel, if there is one, still opens. Moisture in the new base reads in the dry range. If the reading or the water test fails, the visit is not closed and a second line is priced before anyone leaves. Permit work, if the diagnosis has moved into hacking, waterproofing, or a new layout, stops here and is repriced through V On Construction Pte. Ltd. UEN 201611708H.
2026 price, brand and lifespan
A sectional rebuild is the spend that keeps the doors and the stone. A waterproof conversion is the spend when the same cabinet has already failed twice. A full kitchen is a layout decision, not a leak decision. Prices below are 2026 Singapore bands for the described scope. They are not a coupon and they are not a guess after an unopened door. A second trade, such as a PUB licensed plumber or an EMA licensed electrician, is named when the law requires it rather than buried inside the labour line. Compare rows by what they include. The planning-life column belongs to that row only.
2026 SGD scope bands
| Scope | What you are paying for | 2026 SGD band | Planning life |
|---|---|---|---|
| Base board only | One sealed plywood or PVC panel, trap checked | S$280 to S$450 | Plywood 5 to 8 years if the leak stays fixed. PVC foam does not swell |
| Base, gable and plinth | Side panel and toe-kick where the leak ran sideways | S$450 to S$700 | Same as the board you choose |
| Full under-sink conversion | PVC foam or aluminium box when the leak was chronic | S$550 to S$900 | PVC or aluminium is the board you stop replacing |
| Whole kitchen carpentry | New boxes and doors, usually not the stone | S$5,000 to S$6,500 | A new kitchen, not a repair |
Brand, material and lifespan
| Option | Where it is used in Singapore | Failure mode in humidity | Planning life |
|---|---|---|---|
| Moisture-resistant plywood | Patch when the leak is fixed and the doors match | Swells again if a hose weeps | 5 to 8 years dry |
| PVC foam board | Dishwasher and chronic trap leaks | Does not swell. Screw holding is lower than plywood | Does not rot |
| Honeycomb aluminium | Light conversion under a heavy sink | Skin dents. Needs the correct fastener | Stable in humidity |
| Stainless carcass | Heavy or commercial-style bowls | Can still rust at a cut edge if it is not the right grade | Longest of the four |
Gas struts and pull-out runners are separate hardware, often S$90 to S$280, and they can share the visit. They are not a reason to replace the kitchen.
Three Singapore property case studies
Three worked jobs show how the same symptom is priced differently in a new BTO, an older resale flat, and a private condo or landed house. The totals are the lines a household actually paid, not a national average. Permit-exempt invoices are issued by Homey Furnishing Pte. Ltd. UEN 202018148K.
Case 1: 4-room BTO in Punggol
The dishwasher hose had wept onto a six-month-old particle base. Doors were perfect. The base and a 200mm strip of gable were replaced in PVC foam, the trap washer was renewed, and the weep hole was left open. Labour and board were S$520. Time was four hours. The stone and the doors stayed.
Case 2: 28-year resale flat in Tampines
The bottle trap had been leaking into a plywood base that had already been patched once. The gable and plinth were soft. Conversion to PVC foam, a new bottle trap, and edge band to the existing door colour was S$760. The gas-riser grille in the next bay was photographed and left uncovered.
Case 3: 2-bed condo in River Valley
A tenant reported a smell. The undermount bowl was still up, but the base was black. The landlord chose a plywood sectional repair at S$410 after the trap was reseated, because the leak was a loose nut rather than a chronic flood. The deposit discussion was the trap, not a new kitchen.
The box, the leak, and the board that replaces it
Frequently Asked Questions
Is a swollen sink cabinet an HDB hacking job?
No. Replacing the base, gable or plinth keeps the layout and does not need a hacking permit. The weep hole and any City Energy gas-riser opening have to stay clear. A new layout is V On Construction Pte. Ltd. UEN 201611708H.
How much should I budget before a full kitchen?
A sectional rebuild is S$280 to S$700. A waterproof conversion is S$550 to S$900. Full kitchen carpentry is typically S$5,000 to S$6,500 before the countertop. Homey Furnishing Pte. Ltd. UEN 202018148K issues the repair invoice.
Plywood or PVC foam?
Plywood when the leak is fixed and you want screw holding and a match. PVC foam when a dishwasher hose or a chronic trap has already killed one base. Aluminium when you want a light box that will not swell.
Can I screw a new base in while the trap is still dripping?
No. The new board will swell or stain. Stop the leak, dry the box, and then fit the panel. A bottle-trap washer is Simple Plumbing Works. A new supply pipe is a PUB Licensed Plumber.
What if the doors are also swollen?
Doors are a separate line. Often they are not. If they are, they can be replaced without new carcasses for the whole kitchen. Photograph the hinge side before you assume the box is scrap.
Will the repair cover the gas riser?
It must not. The inspection panel has to open. If a quote shows a new gable across the riser, that quote is wrong even if the price is attractive.