Answer
HDB Conversion Scheme — Merging 2 Adjacent Flats Into 1 (2026)
The HDB conversion scheme lets you combine 2 adjacent flats on the same floor into a single larger unit. It's rare, expensive, and subject to HDB approval — but it's the only way to get 160–180 sqm of HDB space without buying a jumbo or executive flat.
Answer: You can merge 2 adjacent HDB flats if they share a non-load-bearing wall. Cost: $80K–$150K renovation on top of the second flat's purchase price ($400K–$700K). Approval takes 3–6 months. Converted flats trade at a 10–20% premium over the sum of parts but have a smaller buyer pool on resale. Fewer than 500 converted flats exist in Singapore.
Conversion Cost Breakdown
Assuming two 4-room flats in a mature estate
| Cost Item | Amount |
|---|---|
| Second flat purchase | $400K–$700K |
| BSD on second flat | $9,600–$18,600 |
| HDB application fee | $300–$500 |
| Structural engineer assessment | $2,000–$5,000 |
| Wall hacking + structural work | $5,000–$15,000 |
| Plumbing & electrical re-routing | $10,000–$20,000 |
| Flooring, kitchen, bathroom | $25,000–$45,000 |
| Carpentry, paint, finishes | $10,000–$25,000 |
| Legal fees | $2,500–$4,000 |
| Total (excl. flat purchase) | $65K–$133K |
Add the second flat's purchase price for total outlay. CPF can be used for the flat purchase but not renovation.
Conversion Timeline
| Step | Duration |
|---|---|
| HDB application & eligibility | 4–6 weeks |
| Structural engineer inspection | 2–4 weeks |
| Renovation plan approval | 3–4 weeks |
| Renovation work | 8–12 weeks |
| HDB final inspection | 2–3 weeks |
| Total | 5–7 months |
Run the numbers on your HDB
Before committing to a conversion, know your stamp duty on the second flat and whether the combined cost makes sense vs buying a larger unit outright.
FAQ
What is the HDB conversion scheme?
The HDB conversion scheme allows owners of 2 adjacent HDB flats on the same floor to merge them into a single larger unit. This was more common in the 1980s-1990s when HDB actively facilitated conversions. Today, HDB evaluates applications on a case-by-case basis. The scheme is only available for flats that share a common wall. You cannot merge flats on different floors or across a corridor. Both flats must be owned by the same household or related applicants. The result is typically a 150-180 sqm combined unit (vs 90-110 sqm for a standard 4/5-room). Converted flats are rare — fewer than 500 exist across all of Singapore — which makes them unique in the resale market.
Who is eligible for the HDB conversion scheme?
Eligibility is strict. Both flats must be adjacent on the same floor with a shared structural wall. At least one flat must have completed MOP (5 years). The applicant must be a Singapore Citizen. You must meet HDB's prevailing eligibility conditions — the combined household income ceiling is $14,000/month for BTO, though resale purchases have no ceiling. If you already own one flat and want to buy the adjacent unit to convert, you need HDB's written approval before proceeding. HDB will assess structural feasibility — not all walls can be hacked. Load-bearing walls between units will block the conversion. You also cannot own private property at the time of application.
How much does an HDB conversion cost?
Total costs range from $80,000 to $150,000+. Breakdown: (1) Purchase of second flat — at market resale price, e.g. $400K-$700K for a 4-room in a mature estate. (2) BSD on the second flat — $9,600 on $500K, $12,600 on $600K. (3) HDB conversion application fee — $300-$500. (4) Structural engineering assessment — $2,000-$5,000 (HDB-appointed engineer must certify the wall removal is safe). (5) Renovation to merge — $60,000-$120,000 including hacking the dividing wall ($5K-$15K), re-routing plumbing and electrical ($10K-$20K), new flooring across both units ($8K-$15K), combined kitchen/bathroom remodel ($15K-$30K), and carpentry/painting ($10K-$25K). (6) Legal fees — $2,500-$4,000. The second flat purchase is the largest cost. The renovation alone is roughly 1.5-2x a typical HDB reno because of structural work.
What is the HDB approval process for conversion?
The process takes 3-6 months. Step 1: Submit application to HDB with proof of ownership of both flats (or intent to purchase the adjacent unit). Step 2: HDB assesses eligibility — citizenship, MOP, income ceiling (if applicable), and ownership conditions. Step 3: HDB appoints a structural engineer to inspect the shared wall. If it is load-bearing, the application is rejected. If non-load-bearing or partially removable, HDB issues conditional approval. Step 4: You engage an HDB-registered contractor to submit renovation plans. These must comply with HDB renovation guidelines — no hacking of structural columns, beams, or wet area walls without approval. Step 5: HDB grants final approval. Step 6: Renovation begins (typically 8-12 weeks for a conversion). Step 7: HDB inspects the completed conversion. The flat is then re-registered as a single unit with a new address. Key risk: if the engineer rejects the wall, you cannot proceed and the application fee is non-refundable.
What happens to the lease and valuation after conversion?
The converted flat takes on the shorter remaining lease of the two original flats. If Flat A has 75 years left and Flat B has 70 years, the combined unit has 70 years remaining. This matters for CPF usage (lease must cover buyer to age 95) and bank loans (minimum 20-30 years remaining for full financing). Valuation is interesting: a converted 8-room equivalent (from two 4-rooms) is NOT simply 2x the value of a single 4-room. Typically, converted flats trade at a 10-20% premium over the sum of parts due to rarity and space. A $500K + $500K combination might value at $1.1M-$1.2M as a single unit. However, the buyer pool is small — not many people want or can afford a $1M+ HDB flat. Resale can take 6-12 months vs 3-6 months for standard flats.
Should I convert or just buy a bigger flat?
Math check: a 5-room HDB in a mature estate costs $600K-$750K and gives you 110-120 sqm. A conversion of two 4-rooms costs $500K (second flat) + $100K (renovation) = $600K on top of your existing flat — giving you 160-180 sqm. Total outlay: $1M-$1.2M for a converted unit vs $600K-$750K for a 5-room. You get 50-60% more space but pay 60-80% more. Alternatively, an Executive flat (150-160 sqm) or DBSS unit might give you similar space at $700K-$1M without the conversion hassle. The conversion makes sense if: (1) you love your location and the adjacent flat is available, (2) you need 160+ sqm (large family, home office), (3) you plan to stay 10+ years (resale is slow). It does NOT make sense if: (1) you are doing it purely for investment (illiquid resale), (2) the wall is load-bearing (application will be rejected), or (3) you might move within 5 years.
Related
- HDB Flat Type Comparison — 2-room to 3Gen, sizes and layouts
- HDB Renovation Guidelines 2026 — what you can and cannot hack
- Renovation Budget HDB & Condo — $40K–$65K for 4-room HDB
- HDB Resale Process Timeline — 8–10 weeks OTP to keys
- HDB 5-Room Resale Price 2026 — $580K–$750K median
Last updated Feb 2026. HDB conversion approvals are assessed case-by-case. Costs are indicative based on recent renovation and purchase data. Structural feasibility depends on the specific flats. This is general information, not financial or legal advice.