3 Risks You'll Regret If You Sign a Contract Without Checking the Building Register

When signing a real estate contract, most people pay close attention to the property register, but end up skimming past — or never opening at all — the building register. Unlike the property register, which shows rights (loans, ownership), the building register shows the "real, physical and legal identity" of the building itself.

Not checking the building register leaves you exposed to risks that aren't immediately visible. For example, a unit flagged as an [Illegal Building Modification] can rack up an annual compliance fine against the owner until the violation is fixed — a burden that sometimes ends up passed on to the tenant. Even more serious: a so-called "disguised residential-commercial unit," officially registered as a neighborhood living facility (commercial use) — can look completely like a normal home on the outside, but if the building is later redeveloped, your co-op membership rights hinge on the registered use, and you could end up with a commercial unit or a cash buyout instead of a new apartment.

Here are the 3 key checkpoints for using the building register to spot a "genuinely risky home" — even when the property register looks perfectly clean.

💡 If you also want to dig deeper into the property register itself, see How to Read the Warning Signs in a Korean Property Register.

3 Types of Risky Homes the Building Register Can Reveal

1. A Home Flagged With a Yellow [Illegal Building Modification] Tag

If you pull a building register and see a yellow [Illegal Building Modification] flag in the top-right corner, treat that as an immediate red flag.

• Risks this creates:
  • Loans blocked: Commercial banks will reject jeonse loans and mortgage applications for the unit.
  • No guarantee insurance: Deposit-return guarantee insurance from HUG (Korea Housing & Urban Guarantee Corporation) or SGI gets rejected, increasing the risk of losing your deposit entirely.
  • Compliance fines: The owner is fined annually until the violation is corrected, and this cost can end up passed on to the tenant.
• Common examples: Illegally enclosed balconies, illegal room subdivisions, unauthorized rooftop additions, and similar.

2. A "Home" That's Actually a Registered Commercial Unit

A unit can look exactly like a proper villa or studio from the outside and inside, while its designated use on the building register is actually "neighborhood living facility" (commercial use) — this happens far more often than you'd think, and is sometimes referred to informally as a "disguised residential-commercial unit."

• Risks this creates:
  • No jeonse loan or guarantee insurance: Since it isn't legally residential, you can't get a policy loan like Beotimmok or Didimdol, a standard jeonse loan, or guarantee insurance.
  • Tax and tenant risk: Because it's not classified as a home, you lose out on acquisition tax breaks and other residential tax benefits, and it becomes extremely hard to find your next tenant when you move out — putting you at risk of a delayed deposit refund.

3. A Unit Where the Registered Number Doesn't Match the Front Door

This is when the unit position and number shown on the building register's floor plan don't match the number physically posted on the front door. (For example: the register lists Unit 201, but the actual front door is labeled Unit 202.)

The risk this creates:

• Even if you moved in and filed your move-in registration for "Unit 201" based on the physical front door, if that space is legally Unit 202 on the register, you get zero legal protection as a tenant.
• If the home goes to auction, the tenant can end up recovering not a single won of their deposit — a genuinely catastrophic outcome.

A Practical Checklist for the Building Register Right Before You Sign

1. Get it directly from Government24: Pull it for free, same-day, from the Government24 website or app.
2. Check the [exclusive-use section] register: For multi-unit buildings (apartments, villas, officetels), make sure you pull the "exclusive-use section" register for your specific unit, not the register for the whole building.
3. 3 must-check items:
   • Is there no yellow [Illegal Building Modification] flag in the top corner?
   • Is the designated use clearly listed as "residential" (multi-unit dwelling, apartment, officetel, etc.)?
   • Does the floor area and unit position on the register match the actual home?

FAQ

Q. What's the difference between a building register and a property register?

A property register shows the "rights" side of things — ownership, mortgages. A building register shows the building's "physical and legal reality" — floor area, designated use, and whether it has any illegal modifications. Even if the property register is completely clean, a problem on the building register can get your loan or guarantee-insurance application rejected, so you need to check both.

Q. Where can I get a building register for free?

You can get one instantly and for free through Korea's Government24 website or the Government24 app. For multi-unit buildings (apartments, villas, officetels, etc.), make sure you pull the "exclusive-use section" register for the specific unit you're contracting, not the register for the whole building.