Roof waterproofing | Thermal insulation

GENERAL MEMBRANE modified bitumen membranes are presented as offering higher quality and durability than conventional bitumen membranes and roofing foils. Modifications include SBS, APP and APAO; we work with APP and APAO.

A polyester reinforcement combined with modified bitumen allows the material to stretch by 45–80% without damage. APP and APAO products are designed to remain intact as they age and to withstand demanding conditions. The source product information describes torch application from −30°C and flow at surface temperatures above 150°C.

A natural slate mineral finish protects the surface and makes it walkable. Specific properties and installation limits must match the selected product.

APP, or atactic polypropylene, traces its history to Nobel laureate Professor Natta and developments in polymer molecular chains. It later began to be manufactured specifically for bitumen roofing membranes.

Compared with oxidised bitumen, APP alone only partly improves low-temperature resistance. It is therefore often combined with other polyolefins, such as polyalphaolefins and ethylene-propylene-butene compounds, to improve membrane performance.

SBS modification emerged in the late 1960s and early 1970s. Styrene-butadiene-styrene is a synthetic thermoplastic rubber with linear, star-shaped or cross-linked chains. It generally makes up 8–22% of the bitumen formulation. The material softens readily, making it practical to install and shape without vulcanisation.

SBS membranes are made by continuously impregnating a carrier with distilled bitumen modified by thermoplastic elastomers such as SBS and SIS. An elastic waterproofing compound and dimensionally stable polyester carrier enable high elasticity, with the source describing elongation up to 200% and cold flexibility down to −20°C.

APP formulations contain a range of plastomeric and elastomeric polymers, providing both elastic and plastic properties. Products can achieve cold flexibility at −20 to −25°C, approaching SBS performance. SBS formulations have also developed, with softening points of 120–130°C.

Despite chemical similarities, APP and SBS differ physically and mechanically. SBS offers high elasticity and fatigue resistance, with elongation in the 100–300% range. Compared with APP, it is more sensitive to sunlight, which can cause surface folds without necessarily affecting the underlying layers or long-term elasticity.

APAO membranes combine bitumen modified with amorphous polyalphaolefins and selected stabilising fillers.

This thermoplastic compound uses ethylene, propylene and butene components formulated to combine with bitumen.

Roofing membranes offer a quick, straightforward waterproofing method. They must be separated from incompatible existing coverings and insulation, typically with geotextile. PVC contains plasticisers that can migrate over time, reducing flexibility.

TPO, a thermoplastic polyolefin, is an alternative with different environmental and durability characteristics. PVC and TPO systems can be mechanically fixed or held down with ballast, such as gravel or a green roof, where the design permits.

A roofing membrane is a single-layer waterproof sheet, with or without reinforcement. It is based on plastomers or elastomers and produced using processes such as calendering, extrusion and coating.

Joints use techniques such as hot-air welding or double-sided tape, depending on the system. A single membrane layer can be mechanically fixed to the roof. Appropriate products offer elasticity and resistance to ozone, UV, roots, acid rain and flying sparks.