Translation of Design Drawings for Prefabricated Structures in Old Houses

Currently, design drawings for prefabricated structures in old houses cannot be provided directly, but a popular science explanation can be given by combining typical characteristics and precautions.

Typical Characteristics of Prefabricated Structures in Old Houses

Prefabricated structures in old houses often adopt a brick-concrete prefabricated slab system, with its core structure composed of two main parts:

1. Main load-bearing structure: Primarily consisting of load-bearing walls built with red bricks, with wall thicknesses typically being 240mm or 370mm, bearing vertical loads and transferring them to the foundation. Red bricks, due to their easy availability and low cost, were once the main material for rural and early urban residential buildings.
2. Floor structure: Prefabricated hollow slabs are used for splicing, with slab thicknesses mostly ranging from 120mm to 150mm, and spans adjusted according to room dimensions (e.g., 3.3m, 3.6m, etc.). Slab joints need to be filled tightly with fine aggregate concrete (C20 or above) or cement mortar to reduce the risk of cracking in the later stage. In some cases, reinforcement bars are reserved at both ends of the prefabricated slabs for anchoring to the walls, enhancing the overall structural integrity.

Characteristics of floor plan layout:

• The first floor mainly serves as public space, such as a main hall (for receiving guests or conducting rituals), living room, kitchen, and bedroom suites with independent bathrooms.
• The second floor is mostly used for bedrooms or storage space, with the structural layout remaining consistent between the upper and lower floors to reduce construction complexity.
• Stairs usually adopt prefabricated concrete steps that work in conjunction with the prefabricated slabs, but it should be noted that cracks may easily occur at the corners of the stairwells due to stress concentration.

Defects and Risks of Prefabricated Structures

1. Poor overall integrity: Brick walls and prefabricated slabs are connected through slab joints, lacking the continuous steel reinforcement framework of cast-in-place structures, making them prone to structural failure due to wall collapse or slab joint separation during earthquakes.
2. Weak seismic performance: According to the "Code for Seismic Design of Buildings" (GB50011), brick-concrete prefabricated slab structures have a relatively low seismic resistance level and should be used with caution, especially in earthquake zones with a seismic intensity of 6 degrees or above.
3. Improper slab joint treatment: If the filling material has insufficient strength or is not properly cured, slab joints are prone to cracking, leading to water leakage and seepage problems, and even affecting the floor's load-bearing capacity.
4. Renovation restrictions: It is not advisable to arbitrarily build partition walls or increase dead loads (such as stacking heavy objects) on the prefabricated slab floors, as this may cause slab surface cracking due to local overloading.

Suggestions for Obtaining Design Drawings

If specific design drawings are required, they need to be customized by contacting a professional design unit for structural safety assessment based on local building codes (such as load values and seismic fortification intensity) and the actual needs of the house. The assessment content should include:

• Verification of the existing structure's load-bearing capacity;
• Reinforcement of seismic structural measures (such as adding structural columns and ring beams);
• Slab joint treatment and waterproof node design.

Using general drawings directly without professional assessment may lead to safety hazards due to parameter mismatches, so caution should be exercised.