I. Pre-Construction Preparation: Substrate Treatment Is Critical
The condition of the substrate directly affects the bonding strength between the membrane and the substrate. The following requirements must be strictly met:
Substrate Flatness: The substrate must be solid and flat, with no obvious protrusions (height ≤ 3mm), depressions, or cracks (cracks with width > 0.3mm must first be filled and compacted with repair mortar). For concrete substrates, remove surface laitance and loose particles first.
Substrate Dryness: The substrate moisture content must be ≤ 9% (testing method: Cover 1㎡ of plastic film on the substrate, seal the edges, and leave it for 24 hours. If there is no condensation under the film, it is qualified). A damp substrate can easily cause poor bonding of the membrane, leading to hollow areas or water leakage later.
Substrate Cleanliness: Thoroughly remove dust, oil, and debris (e.g., stones, wood chips) from the substrate. If necessary, rinse with a high-pressure water gun and let it dry. Oil stains must be wiped clean with a neutral detergent to avoid affecting the bonding performance of the self-adhesive layer.
Membrane Pre-Treatment:
Store the membranes in a cool, ventilated place (temperature ≤ 30℃), avoiding direct sunlight, rain, or extrusion. This prevents aging, adhesion, or deformation of the self-adhesive layer.
Inspect the appearance of the membranes before construction. If edge damage, adhesive layer detachment, or holes are found, replace the membranes immediately-do not use unqualified products.
II. In-Construction Operation: Focus on Details to Prevent Leakage
The core of self-adhesive waterproofing membrane construction is "firm bonding, no hollow areas, and tight laps." Pay attention to the following operational key points:
Construction Environment Requirements:
Temperature: The optimal construction temperature is 5℃~35℃. When the temperature is below 5℃, the tackiness of the self-adhesive layer decreases. Preheat the membranes in a warm environment (15℃~20℃) for 1~2 hours in advance, or slightly heat the substrate with a blowtorch (control the flame to avoid scorching the membrane) before paving. When the temperature exceeds 35℃, the membranes tend to soften-avoid stretching during paving to prevent shrinkage and cracking later.
Weather: Construction is prohibited on rainy, snowy days, or in windy conditions (wind force ≥ Level 5). If sudden rain occurs during construction, immediately cover the paved membranes and protect the unfinished area with waterproof cloth. Resume construction only after the substrate is completely dry.
Paving Sequence and Method:
Sequence: Follow the principle of "from lower to higher elevations, and from flat surfaces to vertical surfaces." Prioritize paving waterproofing weak areas such as roof gutters, eaves, internal/external corners, and pipe roots, then pave large-area regions. Lap joints should avoid areas where rainwater accumulates (e.g., gutter bottoms).
Paving: Tear off the bottom release film of the membrane (tear and pave section by section to prevent the membrane from adhering due to early release of the film). Align the membrane with the reference line and pave it slowly. At the same time, use a rubber scraper (or roller) to press firmly from the center of the membrane to both sides to expel air. Ensure there are no hollow areas between the membrane and the substrate (the area of a single hollow must be ≤ 0.2㎡, and the distance from the edge of any hollow to the membrane edge must be ≥ 100mm; otherwise, cut the membrane and repave it).
Lap Joint Treatment:
Lap Width: The lap width for the long side (along the water flow direction) must be ≥ 80mm, and for the short side (perpendicular to the water flow direction) ≥ 100mm. Adjust according to the product manual (lap requirements may vary for membranes of different thicknesses).
Lap Compaction: Before lapping, remove dust from the lap area of the membrane. Tear off the release film of the lap edge (some products have a self-adhesive lap design), and press the lap joint repeatedly with a scraper to ensure the adhesive layers in the lap area are fully integrated, with no air bubbles or gaps. If necessary, apply special sealant along the edge of the lap joint to further enhance sealing.
Reinforcement of Special Areas:
Internal/External Corners: First pave a 500mm-wide additional layer (cut the membrane at a 45° angle, fold outward at external corners, and inward at internal corners). Each side of the additional layer should cover 250mm of the substrate, then pave the large-area membrane to avoid membrane cracking at corners due to stress concentration.
Pipe Roots: First create a "steamed bun-shaped" additional layer (radius ≥ 150mm) around the pipe. Then wrap the membrane around the pipe (height ≥ 250mm), fix it with a metal hoop (to prevent membrane sliding), and finally apply sealant at the joint between the membrane and the pipe.
III. Post-Construction Maintenance: Avoid Damage to Extend Service Life
After the self-adhesive waterproofing membranes are paved, take protective measures to prevent damage during subsequent construction or use, which could affect the waterproofing effect:
Immediate Inspection and Repair:
Within 24 hours after paving, tap the membrane surface lightly with a small hammer. If "hollow sounds" are heard, mark the location, cut the membrane, remove dust from the substrate, reapply special adhesive, and press the membrane firmly.
Inspect lap joints, internal/external corners, pipe roots, and other areas. If poor sealing or membrane damage is found, repair with a patch of the same material (the patch edge must extend ≥ 100mm beyond the damaged area). Press the surrounding area of the patch firmly and apply sealant.
Protection During Subsequent Construction:
If a protective layer (e.g., cement mortar, insulation board) needs to be laid on top of the membrane, do so 48 hours after the membrane is paved (to ensure the adhesive layer is fully cured). During construction, avoid direct contact between sharp tools (e.g., shovels, nails) and the membrane to prevent scratches.
When transporting materials, lay wooden boards or geotextiles on the membrane surface to prevent damage from heavy objects rolling over.
Daily Maintenance:
Conduct regular inspections of waterproofed areas (e.g., roofs, basements). If membrane bulging, cracking, or lap joint detachment is found, repair immediately.
Avoid piling debris or sharp objects on the membrane surface to prevent long-term pressure from causing membrane deformation and failure.
Summary
The precautions for self-adhesive waterproofing membranes focus on "qualified substrate, suitable environment, standardized operation, and post-construction protection." Oversight in any link may lead to waterproofing failure. During construction, strictly follow the product manual and industry standards. If necessary, hire a professional construction team to ensure the durability and reliability of the waterproofing system.
