[Amended] Material event report (rights offering)

What happened

Material Event Report (Decision on Rights Offering) Form 6.4

Sambu Construction Amendment Report August 7, 2026

1. Disclosure document subject to amendment: Material Event Report (Decision on Rights Offering) 2. Original submission date of the disclosure document subject to amendment: June 26, 2026 3. Amendment details Item: Reason for amendment; Before amendment; After amendment Item 3. Total issued shares before the capital increase (shares): Reason - Seoul Bankruptcy Court's approval of fractional-share cancellation; Before 8,506,734; After 8,455,571 Item 20, sub-item 7 (Other matters for reference in investment decisions): Before: Fractional shares of less than 1 share arising from the debt-to-equity conversion will be cancelled without compensation by the administrator with the Bankruptcy Court's permission, and the number of issued shares and capital stock after the debt-to-equity conversion may change due to the fractional-share difference. After: The fractional shares arising from the debt-to-equity conversion were 636 shares, and cancellation without compensation was approved by the Bankruptcy Court on August 7, 2026. An application for cancellation of electronic registration due to the cancellation without compensation will be filed with the Korea Securities Depository in the future.

Material Event Report To: Financial Services Commission Date: June 26, 2026

Company name: Sambu Construction Co., Ltd. Representative Director: Oh Il-rok Head office address: 8th-10th Floor, 25 Jongno 41-gil, Jongno-gu, Seoul (Tel) 02-2036-8000 (Website) http://www.sambu.co.kr Preparer: (Title) Head of Management Support Division (Name) Han Geon (Tel) 02-2036-8000

Decision on Rights Offering

1. Type and number of new shares: Common shares (shares) 115,010,416; Other shares (shares) - 2. Par value per share (KRW): 1,000 3. Total issued shares before the capital increase (shares): Common shares 8,455,571; Other shares - 4. Purpose of raising funds: Facility funds -; Business acquisition funds -; Working capital -; Debt repayment funds -; Funds for acquiring securities of other companies -; Other funds - 5. Capital increase method: Third-party placement * Matters concerning other shares: Basis in articles of incorporation -; Details of the shares -; Other - 6. New share issue price: Common shares (KRW) 1,000; Other shares (KRW) - 7. Reference share price: Common shares -; Other shares - 7-1. Method of calculating the reference share price: Valuation amount for a security with no formed market price 7-2. Discount or premium rate on the reference share price (%): - 7-3. Basis for calculating the discount (premium) rate: - 8. Basis in the articles of incorporation for the third-party placement: Article 9 (Pre-emptive Rights to New Shares), Paragraph 2, Item 6 - Where new shares are issued through the debt-to-equity conversion of rehabilitation security interests and rehabilitation claims 9. Payment date: July 4, 2026 10. Dividend accrual start date for new shares: January 1, 2026 11. Scheduled new share certificate delivery date: - 12. Scheduled listing date of new shares: September 1, 2026 13. Whether this constitutes a backdoor listing due to in-kind contribution: No. Whether there is an in-kind contribution: No. Whether unlisted company shares are included in the in-kind contribution property: Not applicable. In-kind contribution value of shares to be paid in: Amount -; Percentage of total assets for the most recent fiscal year (%) -; Number of shares to be paid in: - 14. Whether backdoor-listing requirements are met: Not applicable 15. Board resolution date (decision date): June 26, 2026. Attendance of independent (outside) directors*: Present -; Absent -. Attendance of auditor (audit committee member): - 16. Whether subject to securities registration statement filing: No 17. Reason for exemption: Under Article 277 of the Debtor Rehabilitation and Bankruptcy Act, where a debtor that is a stock company, or a new company, issues shares or bonds, Article 119 (Registration of Offering or Sale) of the Financial Investment Services and Capital Markets Act does not apply. 18. Whether subject to a short-sale subscription prohibition period: No. Start date -; End date - 19. Whether subject to Fair Trade Commission reporting: Not applicable * For listed companies, this refers to independent directors; for unlisted companies, outside directors. 20. Other matters for reference in investment decisions 1) The company received a decision approving its rehabilitation plan from the Seoul Bankruptcy Court on June 26, 2026 under the Debtor Rehabilitation and Bankruptcy Act, and this rights offering is being carried out pursuant to that rehabilitation plan. 2) Pursuant to Article 260 of the Debtor Rehabilitation and Bankruptcy Act, the company does not require a shareholders' meeting resolution or board approval as stipulated under the Commercial Act and other relevant laws, which are replaced by the Bankruptcy Court's permission or the administrator's report. 3) Pursuant to the approved rehabilitation plan, the company plans to sequentially carry out a first share consolidation (effective date July 1, 2026), a debt-to-equity conversion (effective date July 4, 2026), a second share re-consolidation (effective date July 11, 2026), and a third-party placement rights offering (effective date July 14, 2026 (as stated in the filing)). 4) The "3. Total issued shares before the capital increase" above is the number of shares after the first share consolidation. 5) The scheduled new share listing date in Item 12 above is the date on which the shares will be listed after the share consolidation, debt-to-equity conversion, and share re-consolidation are all completed; it may change depending on administrative procedures, and any change will be re-disclosed immediately. 6) The board resolution date (decision date) in Item 15 above is the date the company received the decision approving the rehabilitation plan from the Bankruptcy Court. 7) The fractional shares arising from the debt-to-equity conversion were 636 shares, and cancellation without compensation was approved by the Bankruptcy Court on August 7, 2026. An application for cancellation of electronic registration due to the cancellation without compensation will be filed with the Korea Securities Depository in the future. 8) The shares issued through this debt-to-equity conversion will be subject to the subsequent share re-consolidation. 9) The implementation procedure for this debt-to-equity conversion will proceed in accordance with the approved rehabilitation plan and may vary depending on the processing by the relevant institutions. 10) If a creditor entitled to be allotted new shares fails to submit the documents required for the new share issuance within the deadline, the relevant shares will be temporarily allotted to the company's issuer management account. A creditor who has not submitted the documents may later receive a transfer of the shares after submitting required documents, such as a certificate confirming a securities account in their own name, to the company pursuant to the Act on Electronic Registration of Stocks, Bonds, etc.

* Where a listed company intends to issue a security for which no market price has been formed on the securities market, the following information is additionally provided (Unit: KRW, %) Trading-suspension-related information: Trading suspension date; Last closing price before suspension (A); Reference share price evaluation method; Valuation amount (B); Change ratio versus closing price (B-A)/A*100; Whether external appraisal was performed; Appraisal institution name 2025-04-01: 347; -; -; -; -; -; -

[Basis and Purpose of the Third-Party Placement] Articles-of-incorporation provision forming the basis; Purpose Article 9 (Pre-emptive Rights to New Shares), Paragraph 2, Item 6 - Where new shares are issued through debt-to-equity conversion of rehabilitation security interests and rehabilitation claims; Improving the financial structure through debt-to-equity conversion

[Specific Use of Funds Raised Through the Third-Party Placement] [For working capital / other funds] (Unit: KRW) Fund use; Details*; Planned amount by year: 2026; 2027; 2028 and after; Total Other funds; Debt-to-equity conversion; -; -; -; - * As this is a debt-to-equity conversion of rehabilitation claims pursuant to the decision approving the rehabilitation plan, there is no cash payment.

[Selection Process, Transaction History, and Allotment Details by Third-Party Placement Recipient] Third-party placement recipient; Relationship with the company or largest shareholder; Selection process; Transactions and plans within 6 months before/after the capital increase decision; Allotted shares (shares); Remarks Korea Asset Trust Co., Ltd.: -; Debt-to-equity conversion; -; 24,262,365; - DYD Co., Ltd.: -; Debt-to-equity conversion; -; 3,825,888; - CRK Co., Ltd.: -; Debt-to-equity conversion; -; 3,221,904; - Hyundai Engineering & Construction Co., Ltd.: -; Debt-to-equity conversion; -; 3,087,994; - Korea Land and Housing Corporation, Busan-Ulsan Regional Headquarters: -; Debt-to-equity conversion; -; 2,481,936; - Heunghwa Co., Ltd.: -; Debt-to-equity conversion; -; 2,232,862; - Daeho Construction Co., Ltd.: -; Debt-to-equity conversion; -; 2,072,632; - Hanulnuri Co., Ltd.: -; Debt-to-equity conversion; -; 2,025,772; - Korea Engineering Consultants Corp.: -; Debt-to-equity conversion; -; 1,962,021; - Danam Electric Co., Ltd.: -; Debt-to-equity conversion; -; 1,705,018; - * Although there are numerous rehabilitation creditors subject to the third-party placement, only the top 10 creditors are listed.