Self-built Prefabricated Slab House Design

The design of self-built prefabricated slab houses requires comprehensive consideration of the floor slab placement direction, type selection, applicable scenarios, and construction details. Reasonable planning can balance safety and economy.

Floor Slab Placement Direction

The direction of floor slab placement should be determined based on the span of the house. It is preferable to build horizontally in the direction with the smaller span, as horizontal floor slabs distribute stress more evenly per unit area, can withstand greater pressure, and can disperse stress during foundation settlement, reducing the risk of structural damage. For example, if the horizontal span of the house is 4 meters and the longitudinal span is 6 meters, the floor slab should be laid horizontally along the 4-meter direction.

Comparison of Floor Slab Types

• Reinforced Concrete Cast-in-place Slab:
  • Advantages: Strong overall integrity, excellent seismic performance, good waterproof and moisture-proof effects; slab thickness can be adjusted according to the span (e.g., 12-15 cm thick for a 4-meter span), with minimal impact on later hole opening or renovation.
  • Limitations: Long construction period (requires formwork, pouring, and curing), high technical requirements; construction cost is 20%-30% higher than that of prefabricated slabs.
• Prefabricated Slab:
  • Advantages: Standardized factory production, fast on-site laying (1-2 days to complete a single-story floor slab), and 15%-20% lower cost than cast-in-place slabs.
  • Limitations: Poor overall integrity, prone to water leakage at slab joints; weak seismic performance (only suitable for areas with a seismic fortification intensity of six degrees); limited local load-bearing capacity (requires additional reinforcement if heavy objects are to be placed).

Applicable Scenario Assessment

• Seismic Fortification Intensity:
  • Six-degree fortification areas (e.g., most rural areas in Sichuan): For houses with two stories or less and small spans, reliable prefabricated slabs can be used, but reinforced concrete ring beams must be installed (spacing ≤ 4 meters) to enhance overall integrity.
  • Seven-degree or higher fortification areas: Prefer cast-in-place slabs to avoid slab joint cracking or collapse caused by earthquakes.
• Room Span:
  • ≤3.6 meters (e.g., ordinary bedrooms): Prefabricated slabs can be勉强 used, but cast-in-place slabs are more stable.
  • 3.6-4.8 meters (e.g., living rooms, master bedrooms): It is recommended to use cast-in-place slabs or thickened prefabricated slabs (thickness ≥ 15 cm) and add structural columns.
  • ≥4.8 meters (e.g., large-span living rooms): Cast-in-place slabs must be used to avoid slab breakage due to excessive span.
• Budget and Time:
  • Sufficient budget and ample time: Choose cast-in-place slabs for higher long-term safety.
  • Limited budget but unwilling to compromise on quality: Adopt a compromise solution—use cast-in-place strips (width ≥ 30 cm) below load-bearing walls and prefabricated slabs in the middle area of the floor slab, reducing costs while ensuring key part strength.

Key Construction Details

• Reinforcement Cover Thickness: When laying prefabricated slabs, the cover thickness of the bottom reinforcement should be ≥ 15 mm to prevent slab cracking caused by reinforcement corrosion; for cast-in-place slabs, it should be ≥ 20 mm to prevent concrete carbonization from affecting durability.
• Slab Joint Treatment: Prefabricated slab joints should be filled with C20 fine aggregate concrete, with a width ≥ 30 mm, and steel wire mesh should be laid to enhance crack resistance.
• Load Limitation: The single-point load on a prefabricated slab house should not exceed 150 kg/m² (e.g., avoid placing large fish tanks or pianos in the middle of the floor slab); otherwise, local reinforcement is required.

Note: Due to their poor seismic performance and short service life (approximately 30-50 years), prefabricated slabs have been banned for use in commercial housing and public buildings in some areas. Self-built houses should be chosen cautiously according to local policies.