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APP Modified Bitumen Waterproofing Membrane Construction Method

Hot‑melt Application Construction Process

Substrate cleaning → Apply base primer → Snap positioning lines → Detail additional layer treatment → Pre‑lay membrane → Hot‑melt full‑surface laying → Lap joint sealing → End‑edge sealing → Water‑holding / water‑spraying test → Protective layer construction

1. Substrate Requirements The substrate shall be firm, flat and dry, free of sanding, hollowing and cracks. Internal and external corners shall be formed into circular arcs with R≥50 mm. Remove dust and oil contamination. Apply base primer and allow it to dry until non‑tacky before construction.
2. Detail Additional Layer Install additional APP membrane layers at corners, pipe bases, drain outlets, expansion joints, eaves gutters and other details. Each side of the additional layer shall be ≥250 mm and fully bonded by hot‑melt.
3. Line‑snapping and Pre‑laying Snap reference lines according to laying direction. Unroll and flatten the membrane to release internal stress, verify lap widths, then roll back the membrane for later use. Lap width: long side ≥100 mm, short side ≥150 mm.
4. Hot‑melt Full‑surface Laying Adopt LPG flame torch to heat both the membrane bottom and substrate simultaneously. Keep the torch nozzle 250‑300 mm away from the membrane and move at constant speed. Roll forward the membrane when the bitumen on its bottom melts to a glossy black mirror‑like surface. Immediately roll with pressure roller from center to both sides to expel air and achieve tight bonding between membrane and substrate. Avoid burning through the membrane and excessive bitumen sagging. Laying modes: Full bonding: full‑range hot‑melt adhesion, commonly used for roofs and basements. Spot / strip bonding: partial hot‑melt bonding to accommodate substrate deformation, mostly applied to basement bottom slabs.
5. Lap Joint Treatment Heat lap sections by hot‑melt as well. Uniform 3‑5 mm molten modified bitumen shall squeeze out from joints to form sealed bead. For sand‑faced / shale‑faced membranes, grind off surface granules at lap positions prior to hot‑melt bonding for tight adhesion.
6. End‑edge Sealing For parapet walls and vertical surfaces, embed membrane ends into pre‑reserved grooves, fasten with metal pressure strips and nails, then seal tightly with sealant. Where no groove is available, fix with metal pressure strips and perform sealing treatment.
7. Water‑holding Test and Protective Layer Carry out 24‑hour water‑holding test upon roof waterproofing completion with zero leakage. PE‑faced membranes must be covered with cement mortar or fine‑aggregate concrete protective layer. Shale / sand‑faced exposed roofs may dispense with protective layers.