Drilling Holes in Beams of Prefabricated Slab Houses

Drilling holes in the beams of prefabricated slab houses must strictly adhere to technical specifications to ensure the safety of the building structure. The following are the specific operational points:

1. Selection of Drilling Location

• Along the length of the beam: Prioritize the middle 1/3 of the span where shear forces are relatively small. Avoid drilling holes at the beam ends (especially near the columns) or at the junctions of primary and secondary beams. These areas have concentrated shear forces, and drilling holes can significantly weaken the shear resistance capacity, increasing structural risks.
• Along the height of the beam:
  • If the visible height of the beam is less than 35 cm (without waist reinforcement), avoid the lower row of longitudinal reinforcement. It is recommended to choose a location more than 8 cm above the lower part of the beam to prevent breaking the main reinforcement.
  • If the visible height of the beam is more than 35 cm (with waist reinforcement), prioritize drilling holes close to the floor slab or 8 cm from the lower edge of the beam. Drilling holes in the lower part of the beam is riskier as it may break the longitudinal reinforcement, while drilling holes in the upper part has a relatively smaller impact on the structure.

2. Limitations on Hole Size and Quantity

• Hole diameter limitation: The diameter of the hole should not exceed 1/4 of the beam's cross-sectional height, and the distance from the centerline of the hole to the beam end and the beam centerline should be no less than 1.5 times the hole diameter. For example, when the beam height is 40 cm, the maximum hole diameter is 10 cm, and the distance from the hole edge to the beam end should be ≥ 15 cm.
• Quantity limitation: The number of holes drilled in the same beam should not exceed 3, and sufficient distance should be maintained between the holes to prevent local stress concentration leading to cracks or damage.

3. Construction Specifications and Precautions

• Avoid main reinforcement: The area within 7 cm of the lower part of the beam is the distribution area of the main reinforcement. Drilling must strictly avoid this area; otherwise, it will directly weaken the load-bearing capacity of the beam.
• Professional construction: It should be carried out by an experienced team using low-vibration tools such as water drills to reduce secondary damage to the beam. Avoid using high-vibration equipment such as impact drills.
• Reinforcement treatment: After drilling holes, install washers according to the hole location and size or conduct load-bearing capacity calculations. If the holes affect structural safety, measures such as carbon fiber reinforcement or steel plate bonding reinforcement should be adopted.
• Structural inspection: Before drilling holes, it is recommended to commission a professional institution to inspect the beam and evaluate the impact of drilling holes on the safety of the house to ensure compliance with requirements such as the "Code for Acceptance of Construction Quality of Building Decoration" (GB50210-2018).

4. Legal and Regulatory Basis The country allows drilling holes during decoration, but it must comply with relevant regulations, and the main load-bearing structure of the house cannot be modified without design confirmation and approval from relevant departments. Unauthorized operations may face legal liabilities.

Summary: Drilling holes in the beams of prefabricated slab houses requires strict control in terms of location, size, quantity, construction, and reinforcement, and structural inspection should be carried out in advance to ensure safety and compliance.