I. Preparation Phase: Proper "Base Layer Treatment" to Eliminate Inherent Risks
Cleaning: First, scrape off floating dust, cement residues, and oil stains from walls and floors-especially debris around pipe roots and floor drains. Use a wire brush or high-pressure water gun for thorough cleaning (avoid scratching the base layer with sharp tools).
Repair: If there are cracks (e.g., cement shrinkage cracks), potholes, or hollowing in the base layer, fill them evenly with cement mortar (1:3 ratio) and let it dry completely before waterproofing. If there is putty on the walls, scrape it off entirely (putty is not waterproof and will cause the waterproof layer to separate from the wall).
Dryness: The moisture content of the base layer must be ≤ 8%. Simple test: Stick transparent tape to the base layer, peel it off after 24 hours, and check if there is moisture on the tape. A damp base layer will prevent the waterproof coating from "adhering firmly," leading to delamination.
Pipe roots: If there are gaps between pipes and concrete, fill them tightly with waterproof plugging compound (fast-setting cement) to form a circular "water stop platform" (about 5mm high), preventing water from seeping through the gaps.
Floor drains: Before installing the floor drain, ensure the drain opening is flush with the floor. Level the surrounding area with cement mortar to prevent water from leaking around the edge of the floor drain.
Floors: Fully cover all areas, including the shower area, toilet area, and under the sink. Extend the waterproof layer under the threshold stone (to prevent water from seeping into the living room through gaps in the threshold stone).
Walls: Determine the height by area-
Shower area (including around bathtubs): The waterproof layer must be ≥ 1.8m high (to prevent water splashing on the wall during bathing and seeping into the wall, causing mold on adjacent walls).
Non-shower areas (e.g., toilet walls, sink walls): The height must be ≥ 1.5m.
If the bathroom has a window, apply the waterproof layer around the window sill and frame (height ≥ 30cm) to prevent rainwater or condensation from seeping in.
II. Material & Construction Phase: Choose the Right Materials + Attend to Details to Avoid "Construction Defects"
Material Selection: Adapt to Bathroom Conditions, Reject "Low-Quality Products"
Bathrooms are damp with continuous water accumulation, so waterproof materials must be "highly impermeable, adhesive, and environmentally friendly." Prioritize the following 2 types (avoid aging asphalt-based materials):
Pitfall Avoidance: Always choose products that meet national standards (GB/T 19250-2013 Polyurethane Waterproof Coatings, GB/T 23445-2017 Polymer Cement Waterproof Coatings). Check for "environmental certifications" (e.g., China Environmental Labeling) on the packaging. Avoid "three-no products" (they easily release VOCs and have a waterproof lifespan of less than 5 years).
Coats and Thickness: Apply at least 2 coats, with a total thickness ≥ 1.5mm (too thin causes leakage). Let the first coat dry completely (about 6-12 hours, depending on material instructions) before applying the second coat. Apply the two coats in "cross directions" (first horizontally, then vertically) to avoid missing gaps.
"Strengthened Treatment" for Key Areas: For internal/external corners, pipe roots, and floor drain surroundings, apply 1-2 extra coats or paste "non-woven fabric/glass fiber cloth" as an additional layer (like a "patch" to enhance crack resistance). The additional layer should be ≥ 20cm wide (covering high-risk leakage areas).
Avoid "Missed Dead Spots": Use a small brush to carefully apply the coating to the junction of walls and floors (internal corners), under the threshold stone, and the bottom of the bathroom door. Do not skip these hard-to-reach corners.
Membrane Selection: Prioritize "self-adhesive modified asphalt membranes" or "PVC waterproof membranes." Ensure the base layer is dry before pasting, and the overlapping width of membranes should be ≥ 10cm (seal overlapping joints with special adhesive).
Avoid Hollowing: Use a scraper to press the membrane from the center to the edges during pasting to expel air, preventing hollowing between the membrane and the base layer (hollowing traps water and causes membrane peeling).
Polyurethane waterproof coatings take 6-12 hours to dry at room temperature.
JS waterproof coatings take 4-8 hours to dry.
Extend drying time in low-temperature or humid environments (use a fan to speed up drying, but avoid baking with open flames).
III. Inspection & Post-Construction Protection: Ensure "No Risks"
Block the floor drain: Use sandbags or special plugs to block the floor drain, ensuring no water loss.
Fill with water: Pour water into the bathroom floor to a height of 3-5cm (just covering the edge of the floor drain) and mark the water level.
Observation time: Maintain the water level for at least 24 hours (48 hours is recommended to detect minor leaks more easily). Check the water level regularly to see if it drops.
Check for leaks: Focus on the ceiling downstairs (corresponding to the bathroom), adjacent walls (especially shower area walls), and pipe roots. If water seepage or dripping is found, rework immediately (scrape off the waterproof layer, reprocess the base layer, redo waterproofing, and repeat the water tightness test).
Floors: Apply a 2-3cm thick cement mortar protective layer (1:3 ratio), smooth the surface, and let it dry before laying floor tiles. Avoid scratching the protective layer with sharp tools during tile laying.
Walls: If using waterproof coatings, tiles can be laid directly (waterproof coatings have good adhesion to tile adhesive). If using membranes, apply a layer of interface agent first, then lay wall tiles to prevent separation between the membrane and tile adhesive.
After tile laying: If drilling holes in the wall (e.g., for towel racks or storage shelves), confirm in advance that there is no waterproof layer at the drilling position (or avoid key waterproof areas). Seal the gaps with glass glue or waterproof plugging compound after drilling.
Daily maintenance: Regularly check if floor/wall tiles have cracks or hollowing. If tiles fall off, first reapply local waterproofing, then re-lay the tiles. Avoid soaking the floor with strong acid/alkali cleaners for a long time (they corrode the waterproof layer).
Summary: Core Principles - "The Base Layer Must Be Solid, Materials Must Be High-Quality, Construction Must Be Meticulous, and Inspection Must Be Strict"
