Heightening of Prefabricated Lintels in Rural Houses

Heightening of prefabricated lintels in rural houses requires careful operation. If it involves the modification of the original beam, the following methods can be referred to. If the height of the prefabricated lintel needs to be adjusted, it must be re-prefabricated, and planning and safety requirements must be met.

Methods for Modifying the Original Beam

1. Installation of Prefabricated Steel Plates Method
   Increase the height by installing prefabricated steel plates on both the upper and lower sides of the original beam. The surface of the original beam needs to be polished and cracks filled. Q235B-grade carbon steel plates (8-15 mm thick) should be selected. After aligning the upper and lower plates, drill holes (12 cm on each side of the beam axis, with a hole diameter slightly larger than the bolt by 0.5 mm). Fill the gaps with epoxy resin structural adhesive (with an injection pressure of 0.3-0.5 MPa). After standing still for 72 hours, conduct a load test (apply pressure at 1.5 times the designed load capacity, observe deformation for 48 hours, and the deflection change rate must be less than L/500). Suitable for heightening ≤ 15 cm, original beam concrete strength ≥ C25, and closed-space modifications.

2. Welding of Additional Section Steel Method
   Use welding technology to join additional section steel to the original beam. First, temporarily support the original beam with hydraulic jacks (the distance between support points should be ≤ 1/3 of the beam span, and the pre-camber should be controlled at 0.1% of the span). The contact surface between the flange of the additional H-section steel and the original beam should have a 45° bevel. The weld leg size should be ≥ 1.2 times the thickness of the section steel flange. The welding sequence should follow the principle of "web first, then flange; short weld first, then long weld," with an interlayer temperature ≤ 200°C. After completion, treat it with a vibration aging device (frequency of 6000-8000 times per minute, time ≥ 30 minutes, amplitude ≤ 1/3 of the material's yield strength), and then hot-dip galvanize the weld area (zinc layer ≥ 85 μm) and apply a protective paint (total dry film thickness ≥ 200 μm). Requires personnel with special operation certificates to operate. Construction is prohibited when the humidity is > 85% or the temperature is < 5°C. No dynamic load is allowed within 24 hours after welding.

3. Full Beam Section Encapsulation with U-shaped Steel Plate Method
   Form a composite structure by encapsulating the entire beam section with a U-shaped steel plate and injecting high-strength grout, which can simultaneously repair beam defects and enhance load-bearing capacity.

Process for Re-prefabricating the Lintel

If the height of the prefabricated lintel needs to be adjusted, it must be re-prefabricated: Lay a plastic film inside the mold to prevent sticking, place the formed steel reinforcement framework, fill in the concrete in batches and compact it with a trowel (ensure that the steel reinforcement is covered by mortar), and finally place it on a vibration table for forming.

Planning and Safety Requirements

Raising the lintel in rural self-built houses must comply with village planning and the "one household, one宅基地 (homestead)" policy. Confirm the homestead use right certificate or legal approval documents, complete the confirmation of property rights for the original house (for historically inherited buildings), ensure that the total area after adding floors does not exceed local standards, does not affect the lighting and ventilation of neighbors, and obtain written consent. Follow the approval process to handle procedures. Ensure the structural safety of the house and avoid placing excessive burdens on the foundation, walls, beams, and columns due to heightening.