How to Build a Bathroom in a Prefabricated Slab House

When building a bathroom in a prefabricated slab house, it is necessary to comprehensively consider key factors such as floor slab load-bearing capacity, drainage, and waterproofing. The following methods can be referred to for construction:

I. Building a partition wall for the bathroom on a prefabricated hollow slab floor

1. Partition wall material selection: Prioritize the use of lightweight materials (such as aerated concrete blocks, light steel keel gypsum boards, etc.) and avoid using heavy materials like red bricks to reduce the load on the floor slab. Before construction, confirm whether the designed load of the floor slab meets the weight requirements of the newly added walls and sanitary fixtures.
2. Floor elevation and drainage: Elevate the entire bathroom floor by about 40 centimeters to reserve space for drainage pipes. The drainage pipes should be laid along the exterior wall, ensuring that the slope meets the specifications (usually not less than 1%). The joints should be tightly sealed to prevent leakage. The elevated part can be backfilled with lightweight filling materials (such as ceramsite concrete) to reduce the structural load.
3. Waterproofing treatment:
   • Base layer treatment: After cleaning the base layers of the floor and walls, apply two coats of a waterproofing agent mixed with cement mortar. Apply the second coat only after the first one has dried completely to form a preliminary waterproof layer.
   • Membrane waterproofing: After the base layer is dry, lay waterproof membranes (such as SBS modified bitumen membranes). Use a flame gun to heat the seams of the membranes to ensure tight adhesion. During backfilling, avoid sharp objects from puncturing the membranes. A protective layer (such as cement mortar) can be covered on the surface of the membranes.
   • Non-woven fabric waterproofing: As an alternative, a layer of cement mortar can be thinly applied on the base layer, and then non-woven fabric can be directly laid to form a flexible waterproof layer.

II. Other construction points

1. Wall masonry: Reserve the positions of the sewage pipes before masonry to avoid damaging the structure by making holes later. The walls can be built in batches. For the bathroom part, build a single-sided wall first, reserve the entrance position, and then build along the door frame. Use the overlapping stacking method at the corners to enhance stability. After masonry is completed, plaster the walls to ensure flatness.
2. Water inlet pipe installation: Before connecting to the elbow, enlarge the holes in the pipes and use PVC special adhesive to connect the pipes. When making the diversion equipment, the water flow is introduced from the main pipe and then divided into two paths: one flows to the toilet, and the other flows to the washbasin. Elbows are connected below the two pipes, and independent switches are installed to control the water flow.

III. Precautions
Before construction, check the structural drawings of the prefabricated slab house to confirm the type of the floor slab (such as hollow slab or solid slab) and its load-bearing capacity. If the load-bearing capacity of the floor slab is insufficient, it is necessary to reinforce it (such as by pasting carbon fiber cloth) or adjust the design plan (such as reducing the area of the bathroom) to meet safety requirements. In addition, after construction is completed, a closed water test (lasting 24-48 hours) should be carried out to check the waterproofing effect and ensure that there is no leakage before proceeding with subsequent decoration.