Safety Appraisal of Prefabricated Slab Houses

The safety appraisal of prefabricated slab houses should focus on structural integrity, component conditions, and usage and modification situations. According to national standards, they are classified into four grades: A, B, C, and D, and renovation plans are formulated based on these grades.

1. Structural Integrity and Foundation Inspection

1. Foundation: Check for obvious settlement marks around the house's ground, whether there are height differences between indoor and outdoor floors, and observe if there are diagonal cracks at the bottom of walls due to uneven foundation settlement. If settlement or cracks exist, they may affect the overall stability of the house.
2. House Tilt: Visually inspect from a certain distance whether the house as a whole shows visible tilt, skewing, or twisting. Tilt may be caused by foundation problems or uneven structural loading and requires further testing.

2. Special Inspection of Core Components

1. Prefabricated Floor Slabs: Observe whether there are horizontal through-cracks on the ceiling or cracks at the joints, check for obvious signs of sinking in the middle of the floor slab, and examine whether the positions where the prefabricated slabs rest on the walls show signs of loose concrete, debris falling off, or exposed and rusted steel bars.
2. Load-Bearing Walls: Focus on checking for vertical or diagonal cracks on load-bearing walls, whether there are cracks and downward deformation at the lintels above door and window openings, and inspect whether the bricks or masonry at the bottom of the ground-floor walls are severely weathered, spalled, or loose. Determine whether the house has ring beams and constructional columns. For brick-concrete prefabricated slab houses of three stories or more, if they are not equipped, the overall seismic resistance and safety will be reduced.
3. Node Connections: Pay attention to whether the supports of the prefabricated slabs on the walls are firm and show no signs of looseness. The standard requires that the support length should not be less than 80mm. Check for separation or cracks at the corners and junctions of walls.

3. 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 or window openings created in load-bearing walls, or the sizes of such openings enlarged.
2. Unauthorized Additions (Increased Load): Check whether additional floors have been built on the roof without permission, mezzanines added, or excessively heavy items stacked on the floor slabs, causing them to be overloaded.
3. Change of Use: If a house originally designed as a residence is converted into a densely populated business premises, the live load increases significantly, which can easily lead to safety accidents.

4. Safety Grade Classification and Disposal

House safety appraisals are classified into four grades (A, B, C, and D) according to national standards, and the disposal direction is determined based on reports issued by正规 (replace with 'authorized' or 'qualified') third parties.