How to Dampproof and Waterproof Prefabricated Houses

Dampproofing and waterproofing of prefabricated houses can be achieved through the following methods, which require a combination of dampproofing and waterproofing measures:

I. Dampproofing Methods

1. Elevated Dampproof Layer with Prefabricated Panels

   • Core Principle: By constructing an elevated layer, the upward path of underground moisture is blocked. The specific method involves pouring ground beams first, then laying bricks on the beams and reserving ventilation pipes, and finally laying prefabricated panels to form a cavity 30-50 centimeters high. Moisture rises to the cavity and dissipates through the ventilation pipes, unable to reach the ground.
   • Optimization Measures: Lay a steel mesh on the prefabricated panels and fill the seams with concrete to enhance structural stability; build a 6-centimeter-thick brick wall around it to form a reinforced concrete enclosure layer, further improving the dampproofing effect.
   • Advantages and Controversies: This method has significant dampproofing and insect-proofing effects and is convenient for later floor pouring and leveling. However, it should be noted that steel bars in a long-term humid environment may have a risk of breakage (still widely used in actual construction).

2. Laying Dampproof Membranes

   • Construction Process: After backfilling and compacting the foundation, first lay a layer of fine sand and gravel for leveling, then cover it with a high-density polyethylene film (PE film or geomembrane) with a thickness of no less than 0.15 millimeters, and finally pour a 10-centimeter-thick concrete cushion.
   • Advantages and Disadvantages: It has a low cost (about one to two thousand yuan) and a short construction period, but its durability is limited. If the backfill contains sharp objects or the groundwater level is too high, the dampproof membrane may be punctured, resulting in a reduced effect.
   • Key Details: The backfill should be screened cleanly, and the overlap width between membranes should be no less than 15 centimeters and sealed with waterproof tape to prevent moisture from seeping in through the gaps.

II. Waterproofing Methods

1. Surface Waterproofing Treatment of Prefabricated Panels

   • Technical Points: Pour 5-8 centimeters of concrete on the prefabricated panels and embed a steel wire mesh to prevent cracking; use the "three-scraping and two-pasting" process (such as asphalt or JS waterproof coating) to apply a waterproof layer, forming a continuous waterproof membrane.
   • Limitations: The cost is relatively high, and the thermal insulation and waterproofing performance of the prefabricated panels themselves are poor, making them prone to leakage after long-term use. If the budget allows, it is recommended to directly add a roof or pour a cast-in-place panel instead of the prefabricated panels.

2. Combination of Elevated Layer and Waterproof Layer

   • Dual Protection Mechanism: Based on the elevated dampproof layer, waterproof the upper ground (such as pouring a concrete cushion and applying a waterproof coating). Moisture is blocked by the elevated layer, and rainwater is intercepted by the waterproof layer, forming a three-dimensional protection system.
   • Applicable Scenarios: Suitable for areas with a high groundwater level or frequent rainfall, which can significantly improve the durability of the house.

Summary and Recommendations:

• Preferred Dampproofing Options: When the budget is sufficient, use the elevated dampproof layer with prefabricated panels, which takes into account insect-proofing and construction convenience; when the budget is tight, choose dampproof membranes, but strictly control the construction details.
• Waterproofing Optimization Directions: If prefabricated panels are to be used, strengthen the surface waterproofing treatment; it is more recommended to replace the prefabricated panels by adding a roof or pouring a cast-in-place panel to improve the waterproofing performance from the root.