Regulation Guide · 2026. 06 · Updated 08
Legalizing Unauthorized Buildings
Effective December 17, 2026
LEA Architects · Junsu Kim, Architect
Why This Matters Now
An illegally extended rooftop, a shed built without notification, a subdivided unit missing from the ledger. Under normal circumstances there is no way to legalize such buildings. Once detected, enforcement penalties are imposed repeatedly every year until the violation is corrected, and restrictions arise on sales and loans as well. According to Ministry of Land, Infrastructure and Transport statistics, unauthorized buildings nationwide grew from roughly 89,000 in 2015 to about 148,000 by the end of 2024, adding 5,000–6,000 buildings a year.
The law that temporarily legalizes such buildings is the Special Act on Consolidation of Specific Buildings. It has legalized 490,000 buildings across five rounds between 1981 and 2014, and the door reopened after 12 years with Act No. 21820, promulgated on June 16, 2026. The effective date is December 17, 2026, running for 18 months from that date.
Statute at a Glance
| Item | Detail |
|---|---|
| Statute Name | Special Act on Consolidation of Specific Buildings |
| Act Number | Act No. 21820 |
| Promulgated | June 16, 2026 |
| Effective | December 17, 2026 (6 months after promulgation) |
| Duration | 18 months from the effective date (applications accepted through June 16, 2028) |
| Cutoff Date | Substantially completed on or before December 31, 2023 |
| Cost of Legalization | 5 installments (≈5 years) of enforcement penalty + architect's fee + acquisition tax |
What Changed Since the 2014 Act
This is a re-enactment after 12 years, but it is not a simple repeat. The scope of eligible buildings has genuinely expanded. Three changes stand out, and together they determine how many more buildings qualify this time.
| Item | 2014 Act | 2026 Act |
|---|---|---|
| Cutoff Date | Completed by Dec 31, 2012 | Completed by Dec 31, 2023 (extended 11 years) |
| Multi-household | ≤85㎡ exclusive area/unit | ≤85㎡ exclusive area/unit (unchanged) |
| Detached House | ≤165㎡ gross floor area | ≤165㎡ gross floor area (up to 330㎡ by ordinance) |
| Multiplex Housing | ≤330㎡ gross floor area | ≤660㎡ gross floor area (doubled) |
| Room Subdivision | Eligibility contested | Explicitly eligible (unauthorized alteration increasing units) |
| Commercial → Residential | Limited | Explicitly eligible (unauthorized use conversion) |
A Practitioner's View from Yongin and Suwon
The doubled 660㎡ limit for multiplex housing has an outsized impact in multiplex-dense areas like Yongin and Suwon. Buildings that narrowly missed eligibility in 2014 now qualify in large numbers. The addition of commercial-to-residential conversion matters just as much: buildings permitted as neighborhood living facilities but actually used as housing now have a path to legalization for the first time.
Four Eligible Building Types
Small-scale residential buildings substantially completed on or before December 31, 2023 are eligible. Each use type has its own floor area ceiling, and exceeding it disqualifies the building regardless of how well it meets other requirements.
01
Multi-household Housing
Individually owned units within one building, commonly called "villas."
≤85㎡ exclusive floor area per unit
02
Detached House
A single-household residence (excludes multiplex housing).
≤165㎡ gross floor area (up to 330㎡ by ordinance)
03 · Newly Expanded
Multiplex Housing
A single owner leasing to multiple tenants (up to 19 units).
≤660㎡ gross floor area (2× the 2014 limit)
04 · Newly Eligible
Neighborhood Facility → Residential
Buildings permitted as neighborhood living facilities but actually used as housing.
Residential scale rules apply + safety/parking requirements
Seven Eligible Violation Types
Below are the representative violation types compiled by the Korea Institute of Registered Architects. Items 6 (room subdivision) and 7 (commercial-to-residential conversion) are new additions explicitly included under this Special Act.
Eligibility Screening Flow
Below is the five-step flow practitioners use to determine eligibility. A single "No" at any step means the building falls outside eligibility, or an exception provision needs to be checked.
Enforcement Penalty Structure
The practical cost of applying is five installments of the enforcement penalty. Any amount already paid through prior assessments is credited. Below is the calculation formula and example scenarios to get a sense of the actual burden.
Per-installment Calculation Formula
Assessed value per ㎡ × 0.5 × Violating floor area × Rate × Ordinance reduction
Enforcement Decree of the Building Act, Art. 115-3 · Rate: unauthorized construction 100% / FAR excess 90% / coverage excess 80%
Reduction Provisions Significantly Lower the Burden
- Residential units of 60㎡ or less may receive up to a 50% reduction by ordinance
- Local ordinance can lower the rate to as low as 60% (check Suwon/Yongin ordinances)
- Prior enforcement penalty payments are credited against the total
- However, a 100% surcharge applies if the violating area exceeds 50㎡ and is used for rental income
Zones Where Legalization Is Not Possible
Buildings within the zones below are generally excluded, as designated under related statutes. However, individual exceptions may apply — for example, buildings completed before the zone designation — so confirmation via the building ledger and land use plan is required.
Development-restricted Zone
Greenbelt
Redevelopment Zone
Reconstruction/redevelopment
Urban Development Zone
Project interference check
Road-adjacent Zone
Road boundary
Forest Conservation
Forestry/public interest use
Military Facility
Protection Zone
Source Water
Protection Zone
Natural Park Zone
Environmental buffer district
The 8-Step Application Process
Legalization does not end with document submission — it proceeds through a building committee review before final use approval. The full process typically takes 3 to 6 months or more, so advance preparation is essential to avoid the intake surge expected right after the effective date.
Cost Structure
Beyond the architect's fee, legalization involves statutory charges and out-of-pocket costs. Actual amounts vary by violation scale, local assessed value, and ordinance, so an individual estimate is prepared at the preliminary review stage.
| Cost Item | How It's Determined | When It's Due |
|---|---|---|
| Architect's Fee | Assessed case-by-case | 3 installments: contract, midpoint, completion |
| 5-year Enforcement Penalty | Set by statutory formula | Lump sum at application |
| Acquisition Tax (extension portion) | ≈3.16% of tax base | Within 60 days of final use approval |
| Structural Safety Certificate | Outsourced, at cost | During document preparation |
| Stamp Duty & Fees | Government fees, at cost | At submission |
| Ancillary Construction (optional) | Case-by-case, if needed | Depending on review outcome |
A Case From Practice
Our detached house project in Sangha-dong, Giheung-gu, Yongin began precisely with a legalization review of an illegal extension. The review found that the existing building coverage ratio was already at its limit, leaving no room for re-extension even after demolishing the illegal portion. We shifted strategy toward an extension permit using growth management plan incentives and completed it lawfully. This was before the current Special Act took effect, but this kind of alternate path remains valid.
Unauthorized building issues have different solutions case by case. The Special Act is not a catch-all, and even buildings that fall outside it may have other paths available — growth management plan incentives, ordinance relaxations, or separate permitting. It is safer to review all currently available paths together rather than simply waiting on the Special Act. View this project →
Next Step
Start With an Eligibility Check
Run a 1-minute self-assessment to get a preliminary read on whether your building qualifies under this Special Act. You can request a consultation alongside your result if needed.
Start the 1-Minute Self-Assessment →Frequently Asked Questions
Q. What is the legalization of an unauthorized building?
It is a system that temporarily legalizes buildings constructed without a permit or notification, or extended or converted without authorization. Once complete, the violation notation on the ledger is removed, enforcement penalties stop, and the owner regains normal ability to sell, mortgage, or borrow against the property.
Q. When does this Special Act take effect?
Act No. 21820 was promulgated on June 16, 2026, and takes effect on December 17, 2026. It runs for 18 months from the effective date, with actual intake opening in stages from early 2027 depending on ordinance readiness.
Q. What kinds of buildings are eligible?
Small-scale residential buildings substantially completed on or before December 31, 2023. Four types qualify: multi-household (≤85㎡/unit), detached (≤165㎡, up to 330㎡ by ordinance), multiplex (≤660㎡), and unauthorized commercial-to-residential conversion.
Q. What changed compared to the 2014 Act?
Three major changes: ① the cutoff date moved from 2012 to 2023, ② the multiplex housing limit doubled from 330㎡ to 660㎡, and ③ room subdivision and commercial-to-residential conversion are now explicitly included as eligible violation types.
Q. Is a building with subdivided rooms eligible?
Yes, this Special Act explicitly includes room subdivision (unauthorized alteration that increased the unit count) among eligible violation types. However, the parking, structural, and septic requirements matching the increased unit count must still be met, with details set by local ordinance.
Q. How much is the enforcement penalty?
Applicants pay five installments (≈5 years) of enforcement penalty upon application. Amounts already paid are credited, and no further payment is required if five installments were already made. Residential units of 60㎡ or less may receive up to a 50% reduction by ordinance.
Q. Are buildings in greenbelt or redevelopment zones eligible?
In principle, buildings in development-restricted zones (greenbelt), redevelopment zones, urban development zones, road-adjacent zones, forest conservation areas, and source water protection zones are excluded. Exceptions exist for buildings completed before the zone designation, so individual confirmation is needed.
Q. What documents are required to apply?
A use approval application, as-built survey drawings and a building plan prepared by an architect, a structural safety certificate, completion-date evidence (aerial photos, utility records), land use consent, and enforcement penalty payment proof. Original design documents are used where available; otherwise drawings are reconstructed from field measurements.
Q. I have a sale or loan coming up — when should I apply?
Applications are accepted through June 16, 2028. However, the process from application to final use approval typically takes 3 to 6 months or more, so if a sale or loan is imminent, it is safer to complete drawing and document preparation before the effective date.
Q. What can I prepare in advance right now?
① Pull the building ledger and check penalty history, ② run a preliminary eligibility review, ③ secure original design documents or complete a field survey, ④ organize enforcement penalty payment history, and ⑤ gather completion-date evidence. In the Yongin area, LEA Architects conducts preliminary reviews.