Does the Roof of Precast Concrete Houses Resist Rain?

The roof of precast concrete houses has poor rain resistance and is prone to leakage. The specific reasons and improvement suggestions are as follows:

Main Reasons for Poor Rain Resistance

1. Defects in Joint Treatment
   Precast concrete panels are assembled from multiple plates, and the joints are weak points for waterproofing. If professional waterproof materials (such as waterproof mortar and sealant) are not used for filling during construction, or if the joint width is not reasonably designed, rainwater can easily penetrate through the gaps. In addition, thermal expansion and contraction caused by seismic activity or temperature changes can further crack the joints, creating leakage channels.

2. Weak Waterproof Layer
   The roof of precast panels usually relies solely on waterproof coatings applied on the surface or waterproof membranes laid as the waterproof layer. If the base layer is not properly treated during construction (such as not cleaning dust and oil stains), or if the waterproof material is of poor quality or the application thickness is insufficient, the waterproof layer is prone to failure in a short period. In cases of self-built rural houses, leakage problems caused by non-standard construction are particularly prominent, with 8 out of 10 households having such hidden dangers.

3. Rapid Material Aging
   Under the influence of environmental factors such as ultraviolet rays and freeze-thaw cycles, the surface concrete of precast concrete panels will gradually carbonize and crack. Their service life is generally only about 10 years. After aging, the crack width can reach several millimeters, and rainwater can directly pour into the room through the cracks during heavy rain.

Short-term Improvement Measures

• Color Steel Roof Covering: Install color steel plates above the precast panels to block rainwater penetration using their corrosion resistance and integrity as metal materials. However, it is necessary to ensure that waterproof treatment is carried out at the fixing screw locations.
• Waterproof Membrane Repair: After removing the aged waterproof layer, re-lay SBS modified asphalt membranes or polymer self-adhesive membranes, with a focus on treating the joints and corners.
• Plastic Film Covering: In emergency situations, thick plastic films can be used to cover the roof temporarily. However, it is necessary to regularly check the fixing situation to prevent them from being blown away by the wind.

Long-term Solution

It is recommended to avoid using precast panels as roofing materials and give priority to cast-in-place concrete roofs. The cast-in-place process can form a seamless integral structure, which is reinforced with double-layer bidirectional steel mesh to enhance crack resistance. Combined with professional waterproof coatings (such as polyurethane) and protective layers, its rain resistance is significantly better than that of precast panels, and its service life can reach more than 30 years.