[Valuation of purchase and sale of roof tops and acquisition of landmines] Risk assessment and ROI calculation of commercial investors’ demolition of “top floors with illegal constructions”

The beauty and sadness of illegal construction on the roof of Greater Taipei

In Taipei City’s Da’an, Xinyi, and Zhongzheng Districts, or New Taipei City’s Banqiao, Zhonghe, Sanchong and other elite areas, it is common to see numerous 4- and 5-story apartments with an additional layer of iron or cement structures on the top floors. For many home buyers with limited budgets or real estate investors who want to earn a high rental return on investment (ROI), top-end properties represent "buy one, get one free" space or extremely attractive rental income. However, in the Greater Taipei real estate market, Dingjia is essentially an illegal construction (illegal construction), and its value estimation, holding risks and legal liabilities are extremely complex. For investors who are oriented towards commercial acquisitions, if they do not have a thorough understanding of the regulatory red lines, they are likely to face forced demolition soon after the acquisition.

Fact check: Time point for determining “existing illegal construction” in Taipei and New Taipei City

The key to whether Tingjia can "suspend demolition" lies in the construction time identified on the construction permit or aerial survey map. Taipei City and New Taipei City have completely different time lines for identifying "existing illegal construction":

• Standards for existing illegal construction in Taipei City: Illegal construction that existed before December 31, 1994. Tingjia built before this point in time will, in principle, be "photographed and listed for management, and demolition will be postponed." However, illegal construction that occurred after January 1, 1984, is classified as "new illegal construction" and adopts a "demolish upon reporting" policy.
• Existing illegal construction standards in New Taipei City: Illegal construction that existed before June 25, 1998 (2009). Before this point in time, the builders listed existing illegal buildings as existing illegal buildings, which were photographed, listed, and demolished in phases. New illegal buildings after June 26, 1998 were also reported and demolished immediately.

[Reminder of Legal Facts] The "listed and delayed demolition" of an existing illegal building does not mean that the building is "legalized". Legally, it is still an illegal construction and may face the risk of demolition at any time due to policy changes, neighborhood reports involving the police, or interference with the rights and interests of others.

Public Security Red Line: Multiple apartment rentals are listed as "priority forced demolition" landmines

Many purchasers or leasing companies divide the purchased condominiums into three or more suites or rooms for rent in order to create a monthly cash flow of tens of thousands of yuan. However, the Construction Management Office of Shuangbei City Government has strict public security restrictions on this. No matter how old the "existing illegal construction" is, once it is found to have the following circumstances, it will be directly listed as a target of "priority compulsory demolition that endangers public safety":

1. Too many partitions: The top floor is divided into more than 3 units (suites or private rooms), or has more than 3 independent beds. Due to the dense population and restricted escape routes, it is judged to be a high public security risk.
2. Hindering evacuation: The roof-top structure occupies the evacuation platform (at least 1/2 of the roof platform should be left as an open space for evacuation), and there is no qualified fire smoke alarm installed.
3. Covering with more than two layers: Adding another layer on top of the top (commonly known as adding a roof on top) will be removed immediately.

Therefore, when evaluating an acquisition, investors must check whether the internal layout violates the public security red line, and do not blindly pursue rental income from suites while ignoring the risk of demolition of the entire building.

Business Valuation: Discount formula and ROI calculation for rooftop buildings in Greater Taipei

In the practice of real estate valuation and commercial acquisition, there is no title for the registration of the top floor, and its square footage value usually cannot be calculated based on the legal unit price of the building. The top-plus valuation formula commonly used in the industry is as follows:

The value of the additional square footage = the unit price per square meter of the legal main building × (1/3 to 1/2)

For example, if the market price of the main building on the 4th floor of an apartment in Taipei City is NT$600,000 per square meter, the additional square footage on the roof of the fifth floor is usually only calculated at NT$200,000 to 300,000 per square meter during valuation. When calculating return on investment (ROI), merchants should include "demolition risk reserves" and "pipeline renewal wages" in the discount model:

• Asset restructuring cost (CapEx): Most of the old overhead pipelines are shared with the downstairs. After the acquisition, the entire room’s water, electricity and water leakage projects will be carried out. The modification cost is about 80,000 to 120,000 yuan per square meter.
• Rental income assessment: If it is converted into two legal double suites, taking Zhongshan District in Taipei City as an example, the monthly rent for each room is about 15,000 to 18,000 yuan, and the total annual rental income is about 360,000 to 430,000 yuan. After deducting maintenance, water, electricity and possible prosecution losses, the net rental yield (Net Yield) can usually reach 6% - 8%, which is much higher than the 2% of ordinary residential properties.

Businessmen’s long-term asset thinking: best practices for avoiding pitfalls and preventing prosecutions

Experienced real estate investors and asset management companies will take the following "risk control" steps when acquiring Tingjia properties:

First of all, add an "unauthorized construction exemption or compensation clause" to the sales contract, stipulating that if the house is forcibly demolished within a certain period of time after the handover due to reasons that are not attributable to the buyer, the seller must compensate part of the price. Secondly, the appearance and height will not be changed when repairs are carried out, and permanent building materials such as cement and red bricks will be avoided. Instead, lightweight materials such as light steel frames and fire-resistant gypsum boards will be used, and good relations with the neighbors downstairs will be actively maintained (such as sharing the cleaning costs of public stairs and proactively repairing the waterproof layer on the entire top floor). Only through these low-key and professional risk controls can we remain invincible in the water and electricity repair and real estate markets in Greater Taipei.

The latest standards for catching leaks and regulatory responsibilities in Shuangbei collective housing (2025-2026 practice)

According to Article 10 of the "Apartment Building Management Regulations" of the Ministry of the Interior and the trend of civil water leakage judgments in Shuangbei District Court in recent years, most water leakage disputes in old collective housing focus on the identification and definition of "exclusive parts" and "common parts". The roof platform and the public pipes are jointly owned by all separate owners, and the repair costs should be shared by public funds or all residents in proportion to their shares according to law; if the water supply and drainage pipes inside the floor slabs on the upper and lower floors are damaged, the pipes will be borne exclusively by the users or shared by the upper and lower floors.

At the engineering and technical level, modern professional leak detection has fully introduced non-destructive scientific testing, including "FLIR high-resolution infrared thermal imaging camera" (locating temperature difference leakage paths), "high frequency moisture meter" (measuring the moisture content of deep structures) and "pipeline air pressure and water pressure pressure test" (determining whether hot and cold water pipes are leaking). During construction, do not directly apply elastic cement or oil-based paint on the wet cement layer to seal it. Otherwise, the thermal expansion of internal water vapor will quickly cause the coating to blister and peel off, resulting in more serious powdery wall cancer. The standard construction method must first completely eliminate the water source, wait until the moisture content of the cement structure drops below 8%, and then apply the negative pressure resistant silicic acid permeability crystallized waterproof layer.

Recommendations on independent certificate storage and compensation process for water leakage repair

1. Take photos and videos as evidence immediately: Use rulers to record the leakage range, frequency of water discharge, direction of water mark diffusion, and keep time stamps.
2. Written notification and coordination survey: Officially notify the neighbors through the management committee or a certified letter, and agree on a professional third-party leak detection and appraisal unit recognized by both parties to conduct an on-site survey.
3. The contract states the warranty terms: When signing the contract for the project, be sure to clearly specify the waterproofing warranty period (usually 1 year for partial repairs, and 2 to 5 years for the whole room or roof re-construction), and specify the water test acceptance criteria (such as a 48-hour water storage test in the bathroom shower area) to protect your own asset rights.