How Much Does a House's Prefabricated Slab Sink

It is generally normal for the sinking amount of a house's prefabricated slab to be within 20 millimeters. If it exceeds 20 millimeters, different measures need to be taken according to the specific value, and if it exceeds 50 millimeters, it may be classified as a dangerous building.

According to building safety regulations, there are clear grading standards for the sinking amount of a house's prefabricated slab (floor slab). When the sinking amount is within 20 millimeters, it is within the normal range. This value represents slight deformation caused by natural material aging, load effects, or environmental factors (such as temperature changes and humidity fluctuations) during the long-term use of the building structure. It usually does not have a significant impact on structural safety and does not require special treatment, but regular observation of the change trend is necessary.

When the sinking amount exceeds 20 millimeters, attention should be paid and it should be handled on a case-by-case basis:

• Between 20 and 50 millimeters: At this point, the floor slab deformation has exceeded the normal allowable range and may be accompanied by phenomena such as cracks, abnormal noises, or uneven local settlement. It is necessary to immediately contact a professional structural inspection agency to measure the sinking rate with instruments, analyze the causes of settlement (such as foundation problems, overloading, or construction quality defects), and evaluate the impact on the overall structural safety. Depending on the evaluation results, measures such as foundation reinforcement, additional support installation, or local repair may be required.
• Reaching or exceeding 50 millimeters (5 centimeters): According to regulations, at this point, the floor slab sinking has posed a serious safety hazard and may be classified as a dangerous building. It is necessary to immediately stop using the relevant area and entrust a qualified unit to conduct a comprehensive structural inspection and formulate a repair or reinforcement plan. If the sinking is accompanied by other structural damages such as wall cracks and beam-column deformation, priority should be given to handling the critical parts to prevent collapse risks.

Special case description:
There is no need to be overly nervous about a 2-centimeter (20-millimeter) sinking of an ordinary floor slab, but continuous monitoring is required; if the sinking amount exceeds 5 centimeters (50 millimeters), it should be handled according to the standards for dangerous buildings even if there are no other obvious damages. In addition, the judgment of the sinking amount should be comprehensively analyzed in combination with the floor slab span, load type (such as residential, commercial, or industrial use), and design standards. For example, large-span floor slabs are more sensitive to sinking and require stricter control indicators.