Do Prefabricated Houses Need Foundation Excavation?

Whether prefabricated houses require foundation excavation depends on specific circumstances and is not an absolute necessity or non-necessity. The core influencing factors include the size, weight, usage scenarios of the concrete prefabricated components, as well as geological conditions, etc. A comprehensive assessment is needed to determine the construction plan. Here is a detailed analysis:

I. Light and Small Prefabricated Components: No Traditional Foundation Required, but Basic Ground Treatment is Necessary

When the prefabricated components are relatively small in volume and light in weight (such as single-story prefabricated panel houses and temporary buildings), traditional foundation excavation is usually not required. However, to ensure structural stability, basic ground treatment is still necessary:

• Laying a Sub-base: Lay a 10-20 cm thick layer of crushed stone, gravel, or concrete at the foundation location, and compact it to form a flat and solid supporting surface.
• Damp-proofing Treatment: Lay a damp-proof membrane or waterproof coating on top of the sub-base to prevent ground moisture from eroding the bottom of the prefabricated components.
• Level Calibration: Use a laser level to ensure that the flatness error of the sub-base surface does not exceed ±5 mm, preventing deformation of the components due to uneven stress.
  This type of treatment is suitable for low-rise, light-load temporary or auxiliary buildings, such as temporary construction site offices and storage sheds, with a typical design lifespan of no more than 10 years.

II. Large and Heavy Prefabricated Components: Professional Foundation Excavation is Mandatory

For multi-story prefabricated houses (such as three stories or more), industrial plants, or buildings carrying heavy equipment, professional foundation excavation is required according to geological conditions:

• Geological Survey: Determine the foundation depth by drilling and sampling to analyze soil bearing capacity, groundwater level, and permafrost depth. For example, in soft soil foundations, excavation is needed to reach the bearing layer (such as sand and gravel layers or rock layers).
• Selection of Foundation Types:
  • Isolated Footings: Suitable for column-based load-bearing, with individual foundation trenches excavated for each column position, typically with a depth of 0.8-1.5 meters.
  • Raft Foundations: Used for overall load-bearing, with continuous foundation trenches excavated and reinforced concrete slabs poured, with a thickness of no less than 20 cm.
  • Pile Foundations: In complex geological conditions (such as backfill soil or silt layers), prefabricated piles or cast-in-place piles need to be driven in, with depths ranging from several meters to tens of meters.
• Size Requirements: The foundation width should be 10-20% wider than the design width (for example, if the design width is 1 meter, the actual excavation should be 1.1-1.2 meters) to provide operating space and ensure edge bearing capacity.

III. Adaptive Adjustments for Special Scenarios

• Temporary Buildings: If the prefabricated house is for short-term use (such as 3-5 years), detachable foundations such as steel screw piles or prefabricated concrete blocks can be used for easy removal and relocation later.
• Seismic Requirements: In earthquake-prone areas, the foundation needs to be deepened and reinforced concrete ring beams added to improve overall structural integrity.
• Environmental Constraints: In rocky foundations or permafrost areas, blasting or thermal melting techniques need to be used to treat the foundation base to ensure reliable connection with the prefabricated components.