Inspection of Prefabricated Slab Houses

The inspection of prefabricated slab houses should be carried out comprehensively from three dimensions: structural integrity, condition of core components, and unauthorized modifications and usage environment. The specific steps are as follows:

I. Structural Integrity and Foundation Inspection

1. Foundation: Focus on checking for obvious settlement marks around the house, such as ground cracking, sinking, or differences in indoor and outdoor ground levels. Observe whether there are diagonal cracks at the bottom of the walls caused by uneven foundation settlement. These cracks usually extend at a 45° angle and may be accompanied by slight wall tilting.
2. House Tilt: Stand 10-15 meters away from the house and visually inspect for any visible tilting or distortion. If the house is significantly tilted, it may be accompanied by problems such as doors and windows not closing properly and cracks appearing at the junctions of walls and the ground.

II. Special Inspection of Core Components

1. Prefabricated Floor Slabs:
   • Bottom Cracks: Look up at the ceiling (bottom of the prefabricated slab) and focus on checking for horizontal through-cracks or obvious cracking at the joints between slabs. These cracks may be caused by uneven stress on the slab or concrete aging.
   • Deflection and Deformation: Check whether there are signs of downward bending or sinking in the middle area of the slab. You can use a level or a string to measure the flatness. If the deflection exceeds the allowable value in the code (e.g., L/250, where L is the slab span), be alert to structural safety issues.
   • End Damage: Examine the positions where the prefabricated slabs rest on the walls. If the concrete is loose, crumbling, or the steel bars are exposed and rusted, it may be due to long-term moisture exposure or excessive load, and timely repair is required.
2. Load-Bearing Walls:
   • Stress Cracks: Focus on checking for vertical or diagonal cracks in the load-bearing walls, or cracking and downward deformation of the lintels above door and window openings. These cracks may be caused by insufficient wall bearing capacity or earthquake action.
   • Wall Weathering: Observe whether the bricks or masonry at the bottom of the wall are severely weathered and flaking. If the loose depth exceeds 1/4 of the brick thickness, reinforcement is required.
   • Structural Measures: Confirm whether the house is equipped with ring beams and constructional columns (especially for brick-concrete prefabricated slab houses of 3 stories or more). If not, the overall seismic resistance and safety will be significantly reduced, and professional evaluation is required to assess the necessity of reinforcement.
3. Node Connections:
   • Lap Length: Check whether the support length of the prefabricated slabs on the brick walls complies with the code (should not be less than 80mm). Insufficient support may cause the slab to slide or fall off.
   • Tie Conditions: Check whether the corners and junctions of the walls are separated or cracked. These problems may be caused by rusting of the connecting steel bars or construction defects and require timely repair.

III. Inspection of Unauthorized Modifications and Usage Environment

1. Removal or Modification of Load-Bearing Walls: Verify whether the house has had load-bearing walls removed without authorization, door and window openings created in load-bearing walls, or the size of openings enlarged. Such actions will severely weaken the structural bearing capacity.
2. Unauthorized Additions (Increased Load): Check whether additional floors have been built on the roof without permission, mezzanines added, or heavy equipment or large water tanks stacked on the floor. Overloading may cause the floor to crack or collapse.
3. Change of Use: If a house originally designed as a residence is converted into a place with a large number of people (such as a restaurant or KTV), the significant increase in live load may cause safety accidents, and professional evaluation is required to assess the structural safety.

Tip: Some regions conduct safety evaluations of prefabricated slab houses. Class C dilapidated houses require repair and reinforcement, and Class D dilapidated houses should, in principle, be demolished and rebuilt. It is recommended to regularly commission a professional institution for inspection to ensure living safety.