How to Handle the Joints of Prefabricated Floor Slabs in Houses

The treatment of joints in prefabricated floor slabs in houses should be selected based on the size of the cracks, leakage conditions, and usage requirements. Common treatment methods are as follows:

I. Regular Joint Treatment

1. Filling with Joint Sealant
   Use joint sealants made of materials such as epoxy resin or polyurethane to directly fill the joints. These materials have strong adhesion and high durability, enhancing the overall stability of the floor slab and are suitable for minor cracks or preventive treatment.

2. Waterproofing Treatment
   Lay waterproof membranes (such as SBS modified bitumen membranes) or apply waterproof coatings (such as polyurethane waterproof coatings) at the joints to form a continuous waterproof layer. This method effectively blocks water penetration, preventing the floor slab from getting damp and moldy, especially suitable for wet areas like bathrooms and kitchens.

3. Installing Sealing Strips
   Select rubber or silicone sealing strips to be embedded in the joints, filling the gaps through elastic deformation to prevent dust and moisture from entering. The sealing strips should match the size of the joints, and their aging condition should be regularly checked after installation for timely replacement.

4. Reinforcing with Joint Tape
   Rubber or plastic joint tapes can fill the joints and enhance earthquake resistance and crack resistance while blocking sound and heat transfer. During installation, ensure that the joint tape is tightly adhered to the joints to avoid hollowing.

5. Slope Transition Treatment
   For large-area joints, a smooth transition can be achieved by setting up slopes (with a slope ratio of ≤1:50) to enhance the aesthetic appeal of the floor slab. The slope material should be compatible with the floor slab material, and the surface treatment should be flat.

II. Crack Repair and Reinforcement

1. Repair with Fine Aggregate Concrete
   If the cracks are slightly larger and there is leakage, the joints should be chiseled open (5 cm on each side of the surface layer) to form a sloped joint surface and roughen the surface of the prefabricated slab. After cleaning, apply pure cement mortar (with a water-cement ratio of 0.4-0.5), pour fine aggregate concrete twice to a position 1 cm from the slab surface, compact and level it, and then cure it for 2-3 days, during which no treading is allowed.

2. Treatment with Non-shrinking Epoxy Structural Adhesive
   When assembling prefabricated slabs, prioritize using non-shrinking epoxy structural assembly adhesive to reduce the risk of cracks. If cracks have already appeared, use a wall planer to plane off the surface plaster by more than 10 cm, chisel out an inverted V-shaped notch and clean the dust, use repair adhesive for leveling, then apply carbon fiber impregnating adhesive, paste carbon fiber cloth and scrape off air bubbles, and finally apply modified epoxy impregnating adhesive for reinforcement.

III. Precautions

• Material Selection: Choose materials with strong weather resistance according to the usage environment (such as wet or high-temperature conditions). For example, polyurethane waterproof coatings are suitable for long-term immersion environments.
• Construction Specifications: Thoroughly clean the joints before treatment to ensure no dust or oil stains; cure the repaired areas according to specifications to avoid secondary cracking caused by early loads.
• Regular Inspection: Regularly inspect the treated joints and promptly repair any aging or cracking to extend the service life of the floor slab.