TORCH-ON BITUMEN TORCH-ON BITUMEN MEMBRANE WATERPROOFING

Derbigum has been a leading producer of high-quality waterproofing membranes since 1932, specifically engineered for various climatic conditions, including the extreme environments found in South Africa. Assistance in product evaluation has been provided by reputable institutions to ensure optimal performance.

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Derbigum membranes consist of a high-quality polyester or fiberglass reinforcement, which serves as the core or "carrier" of the product. This core is impregnated with SABS-certified bitumen modified with APP (Atactic Polypropylene) and other components that provide flexibility and ultraviolet (UV) light resistance. The weathering surface is treated with mineral granules or sand to provide a key for adhesion of topcoats if aesthetics require. The underside comprises a heat-sensitive polymer film that melts at the correct temperature during application, ensuring a secure bond to the substrate.

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Over millions of square meters of Derbigum membranes have been specified and are successfully performing on roofs throughout Africa and worldwide. The product is fully backed by our manufacturer's guarantee and has a life expectancy exceeding twenty years.

Full literature and references to projects are provided in this brochure.

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Waterproofing System Product Background

Bitumen remains the most important base material for waterproofing today, despite the emergence of numerous "miracle" new products. Bitumen is cost-effective, inherently waterproof, durable, has excellent adhesive properties, and is non-toxic. Examples of five-thousand-year-old applications of bitumen exist in the Middle East, showcasing its longstanding reliability as a waterproofing agent.

Unmodified bitumen has the disadvantage of being brittle at low temperatures and soft or liquid at high temperatures. Flexibility and flow resistance over a temperature range of zero to ninety-five degrees Celsius are prerequisites for South African conditions.

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In-depth research and development have led to the creation of Derbigum APP (Atactic Polypropylene) modified torch-on membranes. Specifically developed for harsh African conditions, Derbigum APP offers the following benefits:

• Vastly Improved Elasticity: Capable of accommodating thermal movements of roofs, particularly required with the increased use of thermally insulated roof decks.

• Enhanced Flexibility at Low Temperatures: Enabling application in cold weather without compromising the membrane's integrity.

• Improved Strength: Allowing for single-ply application while maintaining durability and performance.

• Resistance to Deformation: Improved resistance to permanent deformation, puncture, and tear, providing excellent "walk-on" properties during and after application.

• Crack Bridging Capability: Greater capacity to bridge movements of cracks and joints in the substrate with better fatigue resistance.

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Why Use a Ready-Made Torch-On Membrane?

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Liquid-applied waterproofing systems will always find applications; however, they have inherent disadvantages. Due to unevenness in substrates, it is virtually impossible for the contractor to apply the product uniformly. Some areas may have excess product, while others have less than specified, potentially leading to weak spots and future problems.

Unscrupulous contractors may deliberately under-apply the product without necessarily changing the finished appearance of the roof.

A ready-made membrane eliminates these pitfalls. Derbigum APP is a mechanically produced product of uniform thickness, ensuring consistent performance across the entire surface.

Properties

Physical Properties

• Colour: Black

• Total Solids: 100%

• Specific Gravity: 1.1 – 1.3

• Water Vapour Permeability: Impermeable

• Chemical Resistance: Resistant to mild acids and alkali solutions; not resistant to hydrocarbon solvents or diesel

• Slump Resistance: Will not slump on a vertical surface at 95°C

• Penetration (100g/5s/25°C): 20-30 dmm

• Cold Flexibility (20mm mandrel): ≤ 0°C

• Elongation at 25°C: > 40%

• Tensile Strength: > 500 N/5cm

• Tear Resistance: > 300 N

Applications

• Concrete Roof Decks: See application sheet 1

• Planters and Flower Boxes: See application sheet 2

• Under Screed or Tiles: See application sheet 3

• Water Retaining Structures: See application sheet 4

• Vehicular Traffic Areas: See application sheet 5

Description

Derbigum APP is a torch-on, APP-modified bitumen membrane available in 3mm, 4mm, and 5mm thicknesses, supplied in 10m roll lengths and 1m widths.

Construction

The membrane consists of:

• A heat-sensitive polymer film on the underside to prevent sticking in the roll and to facilitate heat welding during application.

• A high-quality polyester or fiberglass reinforcement that provides dimensional stability and strength.

• A weathering layer of modified bitumen coated with mineral granules or sand to prevent sticking and to supply a surface key for decorative finishing coatings.

WATERPROOFING OF CONCRETE ROOF DECKS

Discussion

Concrete roof decks normally consist of a slab screeded to a fall with a sand-cement mixture. For new structures, a minimum of two rain-free weeks drying period is required before waterproofing. For existing roofs, any existing waterproofing should be removed, and a drying period consistent with the amount of absorbed water allowed. As this is often difficult to estimate, it is suggested that either our technical department is consulted or vent pipes (one per 10 sqm of roof area) are provided to prevent bubbling due to trapped water vapour.

Surface Preparation

All forms of surface contamination must be removed to ensure a clean, smooth surface free of any loose material or barriers to adhesion. Cracks or voids must be filled using appropriate repair mortars and allowed to cure for at least 24 hours. If the parapets are rough, they should be smoothed to receive the flashing. Drain outlets should be inspected to ensure they are functioning correctly.

An assessment should be made regarding potential ponding. Standing water in excess of 5mm is considered excessive. Low areas should be leveled with a suitable leveling compound. Waterproofing over expansion joints should be laid on top of a compatible slip-sheet once the joint has been sealed. Under no circumstances should the waterproofing be laid directly over the expansion joint without proper accommodation.

Application

• Priming: Apply a thin, uniform coating of Derbigum Primer using a paint roller to the entire area, including parapets. Coverage will depend on the substrate's porosity, but approximately 6 sqm per litre of primer should be achieved. Allow a drying period as specified by the primer manufacturer.

• Membrane Installation: Roll out the Derbigum membrane, allowing a 75mm overlap on side joints, 100mm on end joints, and at least 200mm for turn-ups at parapets. Torch the membrane to the substrate, ensuring complete adhesion and that all overlaps are properly sealed.

Flashings

It is recommended that the Derbigum membrane be turned up the parapets by 150mm. An additional flashing strip of 300mm width should overlap the turn-up, with 100mm on the horizontal plane and 200mm on the vertical. This ensures a watertight seal at critical junctions.

Finish Coat

A choice of protective coatings is available:

• Derbicolor Reflective Coating: A reflective mineral finish that provides UV protection and reduces surface temperatures.

• Acrylic Topcoat: Available in various colours for aesthetic enhancement, applied over a sanded membrane surface.

Application

• Reflective Coating: Ensure the surface is clean and free from dust. Apply the coating according to the manufacturer's instructions, ensuring even coverage.

• Acrylic Topcoat: If applying over a hot surface, a primer coat diluted with water may be necessary. Apply the acrylic coating with a paint roller at the recommended coverage rate. Avoid application during wet conditions or onto moist surfaces.

Maintenance

This system is recommended for occasional light foot traffic. The product's life expectancy can be significantly extended by regular inspections and maintenance, including re-coating the roof every 2-3 years or as recommended.

MORE APPLICATIONS:

• WATERPROOFING OF PLANTERS AND FLOWER BOXES

  Derbigum membranes provide excellent waterproofing solutions for planters and flower boxes, preventing water ingress and protecting structural elements from moisture damage.

• WATERPROOFING UNDER SCREED OR TILES

  Ideal for wet areas like balconies and terraces, Derbigum membranes can be applied under screed or tiles to ensure a watertight seal and protect interior spaces.

• WATERPROOFING OF VEHICULAR TRAFFICABLE AREAS

  Specialized Derbigum membranes are designed to withstand vehicular traffic, making them suitable for parking decks and ramps where waterproofing and durability are crucial.

For comprehensive information, technical support, or references to completed projects, please consult the full Derbigum brochure or contact our technical department. Our team is ready to assist you with product selection, application methods, and any other inquiries to ensure the success of your waterproofing projects.