Waterproof membranes are widely used across various industries, and the construction sector, especially in home decoration, has a strong preference for them. But how exactly is the waterproofing membrane applied to building roofs? Let’s take a closer look at the key steps involved in this critical process.
First, it's essential to set up division joints properly. These joints should be placed at the support ends of roof panels, at corners where the roof changes direction, and around any protrusions on the roof. They must align with the existing panel joints to prevent cracks from forming due to temperature changes or structural movement. If the distance between joints exceeds 6 meters, a "V"-shaped joint should be added in the middle, and the depth should go through the entire waterproof layer. In some cases, these joints can also serve as exhaust channels, so they may be widened slightly to allow for proper ventilation. When using materials like asphalt and linoleum, a 200–300 mm wide quilt joint should be added at the seams, sealed with asphalt glue to ensure a tight bond.
Next comes the roof screed construction. This involves creating both a structural slope and a built-up slope. A 3% slope is typically established using a 1:6 cement slag or expanded vermiculite mix, followed by a 25:1 thick cement mortar leveling layer. When setting the slope, make sure the drainage direction is clear and smooth, with the highest point connected to the drain. The thickness of the drain area should not be less than 30 mm, and the concrete should be rolled and pressed to ensure density and stability.
Then, the isolation layer is installed. This layer, often made of two layers of felt and three layers of oil, is placed between the leveling layer and the rigid waterproof layer. It serves as a protective barrier against UV exposure and weathering, helping to prevent aging and ensuring long-term waterproof performance.
When laying the waterproof membrane, several important steps should be followed. First, apply a thin, even coat of treatment agent to the base layer and let it dry before applying the membrane. Laying should start from the lowest point and move upward, following the direction of water flow. If the roof slope is steeper than 10%, the membrane should be laid perpendicular to the ridge. For the application method, remove the release paper, stick the membrane to the surface, and overlap the long edges by 50 mm and short edges by 70 mm. Keep the membrane loose and avoid over-tightening. After placement, use a flat vibrator to compact it, and a rubber hammer for vertical surfaces.
It’s best to carry out the membrane installation when temperatures are above 5°C. Finally, the rigid waterproof layer is constructed using a cold-drawn steel mesh (Ф5@200×200) that is cut at the joints to improve strength and integrity. The steel mesh should be positioned as high as possible within the waterproof layer, with a minimum cover of 10 mm. The fine stone concrete used should have a strength grade of at least C25, with a water-cement ratio no higher than 0.55 and cement with a rating of at least 425. The thickness of the concrete layer should be at least 40 mm to ensure proper hydration and durability. Surface finishing is crucial—avoid adding water or dry cement during the process, as this can lead to cracking and loss of waterproof effectiveness.
After installation, the waterproof layer needs to cure for 12 to 24 hours, with a minimum maintenance period of 14 hours. During the initial curing phase, avoid foot traffic. Proper curing is vital, as poor maintenance can cause early dehydration, reducing strength and increasing the risk of cracks and reduced impermeability. With careful attention to each step, a durable and effective waterproofing system can be achieved.
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