I. What is the construction process?
Base surface cleaning – one coat, application of primer → Joint additional layer treatment → Positioning, marking lines, trial laying → Laying of roofing membrane → Finishing and joint sealing → Cleaning, inspection, and repair → Protective layer construction
II. What are the construction methods?
(1) Base Layer Requirements and Treatment
The base layer must be firm and free from defects such as looseness or sandiness. The surface of the base layer should be flat, clean, and uniform.
Any protruding foreign objects or mortar lumps on the base layer surface must be removed, and dust and debris must be thoroughly cleaned, preferably using high-pressure air. Corners and pipe roots should be cleaned carefully; any oil stains or rust should be removed with sandpaper, wire brushes, or solvents.
If the base layer is uneven or has large pits, it should be leveled with a 1:3 cement mortar mixed with 901 adhesive (15% of the cement weight).
The internal corners where the base layer connects to expansion joints or pipes should be made into uniform, smooth, and even bends or arcs.
The base layer should be dry, with a moisture content preferably less than 9%. The method for determining this is as follows: cover the base layer surface with a 1m square piece of SBS modified bitumen waterproof membrane and let it stand for 2-3 hours. If there are no watermarks on the covered area of the base layer, and no condensation marks on the membrane adhering to the base layer, then the moisture content of the base layer is less than 9%.
(2) Additional Layer Construction: Waterproofing reinforcement treatment should be carried out at joints according to specifications or design requirements; an additional layer of the same membrane must be applied first at internal and external corners, pipe roots, and drain outlets.
(3) Roll material laying
Both the base slab and exterior wall waterproofing are applied using the full-adhesion method.
When laying the waterproofing membrane, follow the membrane configuration plan, starting from one end of the concrete. First, use a chalk line to mark the baseline. The membrane can be laid lengthwise with the adhesive side facing outwards, aligning one side with the baseline; alternatively, roll the adhesive-coated membrane into a cylinder, insert a 30×1500mm iron pipe into the center, have two people hold both ends of the pipe, and fix one end of the membrane in the designated position before laying it along the baseline. During the laying process, the membrane must not be stretched or wrinkled.
Laying the first layer of waterproofing membrane: When laying over a large area, an additional layer should be applied at structural corners, with a minimum overlap of 250mm. Then, mark the dimensions on the leveling layer and begin laying the membrane. The first layer should be laid transversely. The joint width should overlap 80mm on the long side and 100mm on the short side. The membrane should be laid from one side to the other. The membrane must not be folded or stretched. After each sheet is laid, immediately use a clean, soft, long-handled roller to firmly roll it across the substrate, starting from one end, to completely remove any air bubbles between the membrane and the substrate. After inspection and acceptance, proceed with the second layer of membrane.
Laying the second layer of waterproofing membrane: The second layer should be laid in the same direction and using the same method as the first layer, but with staggered joints. It should be pressed firmly together with the first layer, and any protrusions should be secured with cement nails and sealed with cement mortar. Pipe roots should be sealed with sealant and then secured with metal clamps.
The overlap width of the waterproofing membrane layer is crucial to ensuring its quality. The overlap width of the membrane joints should be 100mm. Apply a small amount of adhesive approximately every 1m along the overlap area. After it is basically dry, apply the adhesive evenly to the two bonding surfaces of the unfolded membrane joint with a brush. Leave the adhesive on for about 20 seconds, until it is no longer sticky to the touch. Then, press one side together while removing air bubbles. After bonding, roll it again with a roller.
Additional layers of membrane in special areas should be laid before the main roof membrane application. For example, pipes penetrating walls are the most vulnerable areas prone to leakage; these should be reinforced before laying the membrane.
(4) Termination Treatment of Roll Membrane Ends
The edges and ends of the overlap joints should be sealed tightly with polyurethane sealant or single-component chlorosulfonated polyethylene sealant. Cement mortar mixed with 20% 107 adhesive (based on cement content) can be used for grouting.
III. What precautions should be taken during construction?
The quality of the substrate directly affects the quality of the roll waterproofing layer. The substrate must be firm, flat, clean, and dry, free of loose pits and loose debris; internal and external corners should be rounded into straight arcs.
Before constructing the waterproofing layer, pipes and embedded parts that penetrate walls or slabs must be installed and fixed to avoid damaging the waterproofing layer and leaving leakage risks due to drilling or chiseling after the waterproofing layer is constructed.
When applying the primer, apply a thin, even layer, ensuring no gaps or accumulation. The roll membrane should be laid promptly after the primer dries; otherwise, excessive dust accumulation will require re-coating. The short-side seams of adjacent rolls of waterproofing within the same layer, and all overlaps between upper and lower layers, should be staggered by 1/3 to 1/2 of the roll width to prevent overlapping and uneven application.
When applying large areas of waterproofing, do not remove the transparent release film from the overlapping areas on the back of the roll too early to avoid contaminating the adhesive layer or causing accidental adhesion. If the adhesive film surface is contaminated, it can be cleaned with a specialized primer.
During transportation and storage, the waterproofing should be protected from moisture and heat. The storage area should be dry and well-ventilated, with an ambient temperature not exceeding +35℃. The number of rolls stacked should not exceed 5 layers, otherwise, they may deform under pressure. These measures are beneficial for protecting the release paper and the quality of the waterproofing.
Avoid construction during rain, snow, and winds exceeding level 5.
IV. How to protect finished products?
The laid waterproofing layer should be inspected and recorded promptly, and the protective layer structure should be completed in a timely manner. Wearing shoes with nails is strictly prohibited on the waterproofing layer, and materials should not be piled on it or used as a construction transport route. Pipes and floor drains embedded in the underground waterproofing membrane layer must not be damaged, displaced, or blocked by debris. Prevent water accumulation or contamination of the substrate, which could affect the quality of the membrane installation.
After the membrane installation is completed, a protective layer must be applied promptly. For external waterproofing membranes applied to wall corners, ensure proper protection against breakage and damage, and promptly install protective walls.
During surface layer construction, avoid damaging the waterproofing layer at the junction of protruding pipe roots, floor drains, drainage outlets, etc., with the ground.
