[No need to demolish walls to inspect a medieval house] How to catch leaks without breaking bricks? Popular science "non-destructive moisture meter" and "infrared thermal imaging camera" for non-destructive physical diagnosis of water leakage

The invisible nightmare of antique house transactions: Invisible water pipe leaks in the walls

In the antique house transaction market in the greater Taipei area, elderly apartments and luxury buildings over 20 years old are the main transactions. When buyers look at a home, they are often attracted by the fresh white paint painted by the owner. However, the most elusive trap of buying a house is that the previous owner deliberately hired workers to "paint the surface and cover the walls with dirt" before selling the house, temporarily hiding the signs of mold and water leakage. Once the buyer moves in, 3-6 months later, as the bathroom uses water frequently or during the rainy season, the white paint begins to bubble and fall off, exposing the damp wall cancer behind, and even leaks to the neighbor's house downstairs. How can a buyer protect themselves without being able to break open tiles or dig into walls? The introduction of "non-destructive and non-destructive water leakage physical diagnosis technology" and the use of moisture meters and thermal imaging cameras to scan the inside of the wall are an essential technological defense line for the acceptance and pit prevention of medieval houses.

Non-destructive maintenance principle: Moisture meter resistance method and infrared thermal imaging temperature difference method

To "see through" whether there is water in the wall without damaging the wall tiles, professional house inspectors mainly rely on the following two physical sensing technologies:
1. Non-destructive high-frequency electromagnetic moisture meter (high-frequency impedance measurement):
- The front end of the instrument is equipped with a flat electromagnetic induction plate. When attached to the wall surface, the instrument emits weak high-frequency electromagnetic waves into the wall and measures the "dielectric constant" of the medium inside the wall. The dielectric constant of water (approximately 80) is much higher than that of typical dry cement mortar (approximately 4-6) or tiles. Therefore, once there is moisture in the wall, the dielectric constant will rise sharply, and the instrument pointer will immediately alarm and read a high moisture content value. This can detect hidden water accumulation up to 4 centimeters deep in the tiles, and the homeowner can know the dryness and humidity inside the wall without tapping the tiles.
2. Infrared thermal imaging camera (evaporative cooling temperature difference method):
- When water leakage occurs inside the wall (such as a small leak in the hot and cold water pipe joints, or a rupture of the waterproof layer of the bathroom partition wall), the moisture will spread along the capillary tubes to the outer wall. Due to the heat required to evaporate water (latent heat of evaporation), the surface temperature of a seepage wall will be approximately 1.5°C to 3°C lower than that of an adjacent dry wall surface. Under the lens of an infrared thermal imaging camera, this low-temperature area will appear as a cold "purple-blue color block", which is in sharp contrast with the orange-yellow color of the dry wall. This visual evidence can accurately pinpoint the origin and spread of water leakage.

Key inspection areas for non-destructive inspection of medieval houses

When conducting non-destructive inspections of antique houses, the following three high-risk areas for electric shock and water leakage must be comprehensively scanned:
1. The partition wall outside the bathroom shower area (especially within 30 cm of the wall base) is the location where the waterproof layer is most susceptible to aging. The moisture meter must make continuous impedance measurements along the base of the wall.
2. Check the water supply and drainage pipe joints for tiny drops of water, and use a thermal imager to scan the inside of the pipe room for signs of water leakage from the upper layer.
3. Check whether rainwater on the exterior wall has penetrated into the cement plaster layer through pores.

Budget prices for house inspection and leak detection projects of medieval houses in Shuangbei

In the Shuangbei area, the price of non-destructive water leakage inspection and repair of ancient houses is as follows:
* Depending on the size of the square footage, the cost is approximately NT$ 12,000 to NT$ 22,000 / house. This can serve as legal documentation to require the previous owner to make repairs or reduce the total sale price.
* The cost is approximately NT$ 6,000 to NT$ 10,000 per session.
* Drill holes around the water seepage point, and inject hydrophobic polyurethane foaming agent under high pressure to plug the leaking gap. The cost of labor and materials is about NT$ 1,500 to NT$ 3,000 / needle (usually there is a basic labor fee of NT$ 6,000).

Commercial acquisitions and businessmen’s long-term asset thinking: Non-destructive moisture testing is a golden bargaining chip for bargaining and deductions in the acquisition of medieval old houses

For real estate commercial investors who specialize in buying second-hand apartments in Shuangbei for high-quality flip resale, or planning for long-term commercial management, If a businessman can hire a professional team to conduct a non-destructive moisture meter test before viewing a house and signing a contract, once the moisture content of the bathroom exterior wall is measured to be as high as 15% (which means that the waterproof layer has already failed and needs to be drilled and redone, the CapEx cost will increase by at least 100,000 yuan), the businessman can hold the inspection report and thermal image and directly carry out "overwhelming bargaining deductions" in front of the previous owner and the agent, requesting a reduction in transportation fees or directly deducting 150,000 yuan from the purchase and sale price. On the contrary, if it is discovered after the house is handed over, the businessman will face lengthy litigation and construction delays. This kind of thinking of using technological instruments to calculate invisible repair costs and ensure the lowest entry profit is a required business strategy for improving IRR (internal rate of return) and reducing investment risks in real estate asset management.