The WonderBuilds 4kg Sanded Underlay is a premium waterproofing membrane designed for multi-layer roofing systems. Measuring 8m x 1m, this underlay features fiberglass reinforcement, offering exceptional dimensional stability and durability. Ideal for both new builds and refurbishments, it provides reliable waterproofing with a flow resistance of 120°C and low-temperature flexibility at -10°C.

Easily applied using torch-on methods, this SBS-modified bitumen-coated underlay is suitable for a wide range of substrates. Combining high performance with environmental responsibility, the WonderBuilds 4kg Sanded Underlay is a cost-effective and dependable solution for all your roofing needs.

Why Choose this WonderBuilds 4kg A Film Underlay 8m x 1m?

High-performance waterproofing solution
Fibreglass reinforcement
Quick & easy installation
Strong & durable
Cost-effective

Product Specifications:

Roll Dimensions: 8m x 1m

Material: SBS modified bitumen / fibreglass reinforcement

Weight (kg/m²): 4

Cold Flexibility (°C): -10

Flow Resistance (°C): +120

Tensile Strength (N/50mm): 500 (LD) / 400 (TD)

Elongation at Break (%): 35 (LD) / 35 (TD)

Resistance to Tearing (N): 150 (LD) / 150 (TD)

Dimensional Stability (%): -0.5

External Fire Performance: F Roof

Reaction to Fire: Class F

Watertightness (kPa): 60