What to Do If the Prefabricated Floor Slab of a House Leaks

The best waterproofing treatment for a leaking prefabricated floor slab in a house involves a combination of structural repair and composite waterproof layer treatment, achieving long-lasting waterproofing through steps such as crack cleaning, epoxy resin filling, fiber cloth reinforcement, and surface painting.

1. Crack Pretreatment
   Use an electric pick or angle grinder to chisel along the prefabricated slab cracks, controlling the depth to 4-6 centimeters and the width to accommodate the filling material. Maintain vertical chiseling to avoid damaging the surrounding structure. Then, use a stiff brush (such as a wire brush) to remove dust, loose concrete, and debris from the cracks. If necessary, use high-pressure air to blow out the cracks, ensuring they are dry and free of oil. This step is the foundation for subsequent repairs; if cleaning is not thorough, the filling material may not fully bond with the substrate, leading to ineffective waterproofing.

2. Epoxy Resin Filling
   Mix the main agent and curing agent according to the product instructions to achieve a moderate consistency (flowable but not too thin), ensuring it can penetrate deep into the cracks. Use a small brush to evenly apply the epoxy resin to the inner walls of the cracks, controlling the thickness to 0.5-1 millimeters to form a preliminary bonding layer. Ensure full coverage of all exposed surfaces during application to avoid missed spots. Epoxy resin has high strength and corrosion resistance, effectively sealing the cracks and enhancing structural stability.

3. Hemp Fiber Filling
   Fully immerse fine hemp fibers (or chemical fibers) in the epoxy resin, ensuring the fibers are thoroughly coated with the adhesive. Use a steel bar or specialized tool to slowly fill the soaked hemp fibers into the cracks, compacting each layer tightly with the steel bar after filling. Reserve 2-3 centimeters of space at the filling depth for sealing. Hemp fibers can fill irregular voids in the cracks, enhancing the density of the filling layer and preventing subsequent material settlement or cracking.

4. Cement-Epoxy Mortar Smoothing
   Mix cement and epoxy resin in a 3:1 ratio, adding an appropriate amount of fine sand (particle size ≤ 1 millimeter) and stirring until uniform and lump-free. Fill the remaining cracks with the mortar in 2-3 batches, compacting and smoothing each batch with a trowel. The surface should be slightly higher than the original slab surface by 1-2 millimeters to provide a base for subsequent painting. Cement-epoxy mortar combines strength and waterproofing properties, repairing the cracks and forming a flat surface to avoid local stress concentration.

5. Fiber Cloth Reinforcement
   Select degreased glass fiber cloth for waterproof layer reinforcement. Apply a layer of epoxy resin to the smoothed mortar surface, then lay the fiber cloth flat over the crack area, ensuring no wrinkles or air bubbles. Apply another layer of epoxy resin to cover the fiber cloth. The fiber cloth can disperse structural stress, prevent crack propagation, and enhance the tensile strength of the waterproof layer, extending the lifespan of the waterproofing effect.