High Moisture in Cement Prefabricated Houses

The high moisture problem in cement prefabricated houses can be effectively solved through targeted measures, requiring a comprehensive approach that combines an analysis of moisture sources with moisture-proof design.

Analysis of Moisture Sources

1. Foundation and Structural Issues: In older houses, the foundation may not have been waterproofed, allowing groundwater to seep through the walls via capillary action. The waterproof layer in the joints of prefabricated panels may have aged, leading to water leakage and moisture return.
2. Environmental and Material Factors: The porous structure of cement easily absorbs moisture, leading to condensation when humidity exceeds 60%. During the rainy season or in low-rise buildings with poor ventilation, moisture accumulates. Large temperature differences between indoors and outdoors (such as during winter heating) also increase condensation on walls.
3. Lack of Daily Maintenance: Failing to close windows promptly during rain, not repairing pipe leaks, and allowing corners to remain damp for extended periods exacerbate moisture problems.

Solutions

1. Structural Moisture-Proof Upgrades

   • Foundation Treatment: Check if the moisture-proof layer has failed. If necessary, remove the original coating and apply a penetrating waterproof coating (e.g., Davco K11 waterproofing slurry, with a coating rate of 1.5 kg/㎡ and applied in two coats). In severely damp areas, install a moisture-proof board (thickness ≥ 9 mm calcium silicate board, with a moisture content ≤ 8%).
   • Joint Repair: Seal the joints of prefabricated panels using waterproof glue or epoxy resin to fill aged gaps.

2. Ventilation and Dehumidification Equipment

   • Forced Ventilation: Install a bidirectional ventilation fan (air volume ≥ 150 m³/h) and operate it for 2-3 hours daily. Open windows on sunny days to create a cross-flow, especially from 10 AM to 3 PM.
   • Physical Dehumidification: Use a compression dehumidifier (daily dehumidification capacity of 12 L/day per 20 ㎡), placed at least 50 cm away from walls. For small spaces like closets, place calcium chloride dehumidification boxes (1 box per 3 ㎡, replaced monthly).

3. Wall and Floor Protection

   • Wall Treatment: Remove areas affected by alkali return and mold, clean with a 5% oxalic acid solution, and then spray with an anti-mold agent. Apply a waterproof coating overall to enhance impermeability.
   • Floor Moisture Isolation: Lay a polyethylene moisture-proof pad (thickness ≥ 2 mm) + tiles, with joints filled with epoxy colored sand (water absorption < 0.5%). For rooms with underfloor heating, first install a 2 cm thick XPS extruded polystyrene board insulation layer (thermal conductivity ≤ 0.03 W/(m·k)).

4. Daily Maintenance Tips

   • Close windows tightly during rain, and activate the air conditioner's dehumidification mode when humidity exceeds 70% (set to 26°C + 50% humidity).
   • Regularly check for pipe leaks and place bamboo charcoal packs in corners (exposed to sunlight for 4 hours monthly for reuse).
   • Use a dehumidifier in advance during the rainy season, and monitor with a hygrometer (accuracy ± 3% RH) in real-time.

Moisture-Proof Design Reference (Taking Prefabricated Houses in Hohhot as an Example)

1. Foundation Moisture-Proofing: Lay a waterproof material layer and set up a drainage system around it.
2. Wall Moisture-Proofing: Add waterproofing agents to prefabricated panels, incorporate a moisture-proof layer in the structure, and apply a waterproof coating on the exterior surface.
3. Door and Window Sealing: Use special sealing materials at joints and choose moisture-proof materials (e.g., aluminum alloy + thermal break insulation).
4. Ventilation System: Scientifically design ventilation paths to reduce humidity using natural or mechanical ventilation.