Why Overlap Treatment Is Critical for Bitumen Waterproofing Membranes ?
In SBS modified bitumen and self-adhesive bitumen waterproofing systems, overlap areas are the most common source of leakage. Although these membranes provide excellent waterproofing performance, improper overlap treatment can significantly reduce their effectiveness.
A correctly treated overlap must form a continuous waterproof layer, matching the membrane’s strength, flexibility, and durability. For SBS and self-adhesive systems, this depends heavily on temperature control, material compatibility, and installation accuracy.
Key Preparation Steps Before Treating Bitumen Membrane Overlaps
Substrate Condition and Cleanliness
The substrate at overlap zones must be solid, clean, and free from dust, oil, moisture, or loose particles. Contaminants directly affect bitumen adhesion and bonding strength.
Surface Dryness and Temperature Control
For SBS membranes and self-adhesive bitumen membranes, surface dryness is essential. Excess moisture or low temperatures may weaken bonding performance, especially for self-adhesive layers.
Selection of Compatible Materials
Overlap materials such as bitumen sealants, seam tapes, or primers must be fully compatible with SBS or self-adhesive bitumen membranes to ensure long-term waterproofing stability.
Standard Overlap Treatment Process for SBS & Self-Adhesive Membranes
Pre-Laying and Accurate Alignment
Before bonding, membranes should be dry-laid to confirm alignment. Overlaps must remain straight, flat, and free from folds or tension.
Heating or Activation (for SBS Membranes)
For torch-applied SBS membranes, the overlap area must be evenly heated until the bitumen reaches proper bonding condition. Overheating should be avoided to prevent material damage.
Adhesive Bonding (for Self-Adhesive Membranes)
For self-adhesive bitumen membranes, firm pressure is required to activate the adhesive layer. Rollers should be used to ensure full contact and eliminate trapped air.
Compaction and Sealing
After bonding, overlaps must be compacted using rollers or flat tools. Bitumen should slightly extrude along the seam edge, indicating proper bonding.
Reinforcement at High-Risk Areas
Critical areas such as corners, edges, drains, and movement joints should be reinforced with additional sealing tape or bitumen sealant to enhance waterproofing reliability.
