How to Construct the Foundation of Prefabricated Houses

The construction of the foundation for prefabricated houses mainly includes the following steps:

Site Leveling: Before construction, the site must be thoroughly cleared to remove obstacles such as stones, weeds, and tree roots on the surface. The pits and depressions on the ground should be backfilled and compacted to ensure the site's flatness meets construction requirements. This step provides a stable reference surface for subsequent measurement and layout, preventing foundation positioning errors caused by ground undulations.

Measurement and Layout: Use surveying instruments such as total stations and leveling instruments to determine foundation control points, exterior wall axes, and excavation boundary lines based on design drawings. Mark key positions with ink lines or lime powder, and focus on reviewing parameters such as axis spacing and foundation width to ensure the foundation position fully matches the building layout.

Foundation Trench Excavation: First, use an excavator to conduct probe operations to analyze the soil type of the foundation (such as clay, sand, or rock), and then determine the excavation depth and width according to the load requirements of the prefabricated house. Excavation should be carried out in layers, with each layer not exceeding 0.5 meters in depth. At the same time, reserve 20-30 cm of space for manual bottom cleaning to avoid mechanical disturbance to the foundation soil layer.

Foundation Cushion Construction: Pour a C15-C20 concrete cushion at the bottom of the foundation trench, with a thickness typically ranging from 100-150 mm. During pouring, use a flat vibrator to compact the concrete, and finish the surface with a wooden trowel to ensure flatness, with an error controlled within ±5 mm. For cushion formwork, use steel formwork fixed with diagonal braces to prevent deformation and ensure accurate concrete pouring dimensions.

Reinforcement Processing:

• Rebar Tying: Place main rebars and stirrups according to the design drawings, with a main rebar spacing deviation of ≤10 mm and stirrup hook angles reaching 135°. Use double-strand 22# iron wire for cross-tying, with tying points spaced no more than 200 mm apart.
• Prefabricated Skeleton Installation: For complex foundations, prefabricate rebar skeletons in the factory in advance, transport them to the site, and precisely position them using lifting equipment. Use a laser plumb instrument to calibrate verticality, with a deviation not exceeding H/500 (H being the skeleton height).

Other Treatments:

• Soil Quality Optimization: In clay foundations, support concrete bored piles can be used to enhance connections, with pile diameters ranging from 300-500 mm and spacing of 1.5-2.0 m.
• Drainage Measures: Set up open drainage ditches (width ≥300 mm, slope ≥1%) and collection wells (depth lower than the foundation trench by 1 m), equipped with submersible pumps for continuous drainage. For areas with high groundwater levels, use a well-point dewatering system, maintaining a vacuum pressure above 65 kPa.

Formwork Installation and Concrete Pouring: Use 18 mm thick phenolic resin formwork, reinforced with φ48 steel pipes and tie rods, and seal gaps with double-sided tape. Use C30 ready-mixed concrete for pouring, carried out in layers (each layer thickness ≤500 mm), and compact with an immersion vibrator. Perform secondary surface troweling to reduce shrinkage cracks.

Foundation Testing: After 28 days of curing, conduct tests such as pile foundation low-strain integrity testing (integrity ≥95%) and static load testing (bearing capacity characteristic value ≥1.2 times the design value), and issue a qualified report before proceeding with the construction of the superstructure.