Korean Redevelopment: How a 10% Cost Rise Hits Your Contribution

When total project cost in a Korean redevelopment district rises by 14 billion won, a district whose pre-project assets are appraised at 300 billion won sees its bi-rye-yul (proportion rate) fall by 4.67 percentage points. A member holding 500 million won of appraised property pays 23.3 million won more. The rate is (post-project asset value − total project cost) ÷ pre-project asset value × 100, and the cost increase subtracted from the numerator is distributed to members in proportion to their share of pre-project assets.

Real Estate 114 defines the rate as a measure of how much a member's original asset grows in value through the project, reading above 100% as sound project economics and below 100% as a signal of additional contributions. That reading only holds while the pre-project appraisal is fixed.

What the formula actually divides

Three blocks make up the equation. Post-project asset value is total revenue — members' units plus general-sale units — once construction finishes. Total project cost sums construction, financing and incidental costs. Pre-project asset value is the combined appraised value of what members already owned. Hankyung Business lays out the same formula, illustrating that a member with 500 million won of pre-project assets holds a claim value of 550 million at a 110% rate and 450 million at 90%.

What a member actually pays runs one step further. Claim value equals pre-project appraisal times the rate; the contribution equals the member sale price minus that claim value. The rate does not set the contribution directly — it scales how much of your own asset is recognized.

The valuation date is written into the formula too. According to Korea's Easy Law service, the pre-project prices entered into the management disposal plan are assessed as of the date the project implementation approval is publicly notified. What sits in the denominator is that appraisal, not today's market price.

If construction costs rise 10%, how much more do you pay?

Take a hypothetical district: post-project value 500 billion won, pre-project assets 300 billion won, total project cost 200 billion won, of which construction is 140 billion (70% of the total). The baseline rate is (500 − 200) ÷ 300 = 100.0%. Holding everything else fixed and raising only construction cost, here is what happens to a member with 500 million won of pre-project assets facing an 800 million won member sale price.

One rule falls out of the table. A single member's contribution increase equals the total cost increase multiplied by that member's share of pre-project assets. A 10% construction rise adds 14 billion won of cost; a member with 500 million out of 300 billion holds a 0.167% share. 14 billion × 0.167% = 23.3 million won, matching the table exactly. You can get your own exposure without touching the rate at all.

The heavier the construction share, the sharper the sensitivity. If construction were 85% of total cost (170 billion) instead of 70%, a 10% rise adds 17 billion, pushing total cost to 217 billion. The rate falls to (500 − 217) ÷ 300 = 94.3%, down 5.67 points, and the same member pays 28.3 million won more. The identical headline — “construction up 10%” — lands differently depending on the district's cost structure.

Is 110% always better than 90%?

No. The rate produces different numbers for the same project depending on how the numerator and denominator are drawn. Weekly Korea Housing Economy points out that raising the member sale price from 80% to 90% of the general sale price increases total revenue and lifts the rate while leaving the actual contribution unchanged — and that lowering the pre-project appraisal likewise lifts the rate without changing the contribution.

Running the second case through the district above:

Cut every appraisal by 10% and the rate rises to (500 − 200) ÷ 270 = 111.1%, up 11.1 points. Yet claim value stays at 450 million × 111.1% = 500 million, and the contribution stays at 300 million. A higher rate on its own changed nothing about what the member owes.

The proportion rate is an output of project economics, not a number that decides on its own what you pay.

Comparing rates across districts is therefore close to meaningless; what matters is why a rate moved within one district. If it rose because post-project value grew, there is substance behind it. If it rose because appraisals fell, only the label changed. For the tax side of acquisition, read this alongside how occupancy rights and pre-sale rights differ on acquisition tax and household counting; after completion, the reconstruction levy's exemption threshold and bracket rates apply separately.

When the rate is fixed, and when it moves

The rate is fixed as a planned figure when the management disposal plan is approved, but nothing guarantees it holds to completion. Total project cost moves with construction price increases, design changes, and financing costs from schedule delays; post-project value moves with the sales market. Both sides of the numerator can shift.

The institutional safeguard sits in the general meeting threshold. Easy Law notes that a management disposal plan passes on a simple majority of members, but a project cost increase of 10% or more requires approval from two-thirds. In the table above, a 10% construction rise is only a 7% increase in total cost (14 billion ÷ 200 billion), so it does not trigger the two-thirds rule. In a district where construction is 70% of total cost, construction would have to rise 14.3% to trigger it. Which is why the denominator behind any increase figure on a meeting agenda is worth checking.

What to verify

• The valuation date in the management disposal plan — the appraisal as of the implementation approval notice, not current market price
• If the rate rose against the previous plan, the reason — higher post-project value, or lower pre-project appraisals
• The member sale price as a percentage of the general sale price; this ratio touches real benefit more directly than the rate does
• Construction's share of total cost and any price-escalation clause in the contracting agreement — a higher share means cost rises hit the rate harder
• Whether the project cost increase on the meeting agenda exceeds 10%, which triggers the two-thirds approval requirement
• Your own share of pre-project assets (your appraisal ÷ the district total) — that is the fraction of any cost increase you absorb

Sources

• Hankyung Business — How the proportion rate is calculated and what it means
• Weekly Korea Housing Economy — The traps in the proportion rate
• Real Estate 114 — The proportion rate as a core valuation metric
• Easy Law — Establishing a redevelopment management disposal plan