Overview of Waterproofing Metal Roofs

MRC’s liquid applied waterproofing coatings provide a seamless monolithic waterproof coating to any building envelope, ensuring the reliable repair and elimination of all leaks, whilst also reflecting the sun’s rays and thereby reducing the temperature of the metal roof sheet and the air temperature within the building.

Our waterproofing solutions are easy to apply to metal roof systems, while conveniently ensuring no interruptions in the usual flow of business during application. The system is generally considered when the existing metal roof is either rusty, leaking or coming to the end of its operational life.

Product Selection – Important factors to remember

It’s important to take into account any additional benefits provided by a reliable waterproofing product to maximise on your investment.

MRC’s liquid applied coatings show impressive Light Reflective values, Emissivity and Solar Reflectance making it a perfect, well rounded waterproofing solution. All 3 three factors are key to having the right liquid applied coating to achieve the brief of waterproofing, extending the life of the existing metal roof sheet and providing a reflective barrier. While maximising on the seamless waterproofing protection these products offer, you will enjoy reduced thermal movement and damage due to temperature stability (never exceeding 50⁰C), as well as year round temperature stability and thermal comfort and – drastically reduced energy needs.

MRC Group’s installed liquid applied ‘Cool Roof’ Waterproofing systems, is backed with the unrivalled single source ‘Guardian’ System Warranty which covers design, materials, installation & maintenance for the term of the roofing and cladding system.

Issues associated with leaky and rusty roof sheeting

Some products such as Zinc roof sheets may offer great light reflective values (LRV), however the emissivity of the material may be low – reaching extremely high temperatures of around 80°C – increasing thermal movement and internal air temperature within the building. Zinc roof sheets do reflect some visible light, however it is a porous material which absorbs and stores heat creating hot surfaces and thermal instability. Rather than releasing heat back into the atmosphere this heat is reradiated into the building creating an uncomfortable indoor environment – requiring high energy usage.

As the roof sheeting ages and corrosion starts to break down the material, the metal roof sheets start to absorb more of the heat, which leads to greater thermal expansion and contraction resulting in increased corrosion. As the cordoned metal roof sheets absorb more heat this is reradiated downward into the building increasing the air temperature within the building.

Key Features of Thermal Waterproofing Metal Roofs

  • Reliable weatherproof solutions, Highly durable, Easy installation
  • Heat and UV reflective, Extends roof life, Reduces maintenance costs
  • Reduction of heat gain and solar radiation, Reduces energy needs
  • Avoidance of roof replacement, can be applied to rusted surfaces
  • Reduces greenhouse gas emissions and carbon footprint
  • Reduces thermal expansion a contraction, Rot proof
  • Suitable for new / existing roofs, Maintains low internal temperatures
  • Minimal Maintenance, cost effective, Endures permanent ponding
  • Installation wont interrupt business operations
  • Seamless insulation and waterproofing
  • Tear and impact resistant, temperature stability
  • Fatigue resistant, Compatible with any type of substrate
  • Backed with the up to 20 year ‘Guardian’ System Warranty

Applications of Thermal Liquid applied Waterproofing Metal Roofs

MRC has various waterproofing solutions available offering compatibility with any type of substrate and climate conditions.

  • Roofs, walls, gutters, green roofing systems
  • Domestic homes, factories, warehouses, shopping centres
  • Schools, universities, educational facilities
  • Apartment buildings, Office blocks, Parking Garage
  • Dams and Reservoirs, Bridges, Silo’s
  • Most civil Structures, Beams and columns
  • Stadiums, Museums, Convention Centres

Technical Data of Liquid Applied Thermal Waterproofing Metal Roofs

Liquid Applied Coating Options:

MRC’s liquid applied coatings offer seamless waterproofing protection to exposed surfaces and gutters. These solutions assist in restricting thermal movement and significantly reducing thermal impact damage, while also providing cool-roof technology for indoor comfort and increased productivity.


Light Reflective Values (LRV): indicates the amount of light reflected (and absorbed) by a colour. Colours with an LRV of less than 50% will absorb more light resulting in darker appearing colours and hot surfaces, while lighter colours with an LRV greater than 50% will reflect more visible light – creating a much cooler, temperature stable environment.

MRC’s liquid applied waterproofing systems provide a LRV of 86%


Emissivity: Is the measurement of an object or surface’s ability to release stored heat back into the atmosphere. Some colours absorb more heat than others, however the material of an object / surface is the determining factor in its ability to re-radiate stored heat. A black body would have an emittance value of 1, while a perfect heat reflector would have a value of 0.


Emissivity values of surface materials:

Iron, galvanised sheet 0.23
Aluminium, polished 0.05
Asphalt 0.90
Plaster 0.90
Concrete 0.54
Red Brick 0.85
Glass 0.92
Wood 0.95
Zinc Sheeting 0.20

MRC’s liquid applied waterproofing systems provide a emissivity of 0.86


Solar Reflectance Index (SRI): Indicates the temperature of a surface once it is exposed to sunlight due to its solar reflective capabilities. The SRI of that area is then indicated on a scale of 0 – 100 indicating the reflective value of that surface. For particularly hot or cool surfaces, the SRI can sometimes reflect below 0 or even above 100.

MRC’s liquid applied waterproofing metal roofs provides a SRI of 109.

MRC’s extensive range of Waterproofing Metal Roofs Solutions:-

We have large array of waterproofing systems available for almost every application as follows:-

  • AquaFlect 5, 10 & 20 – High solids polyurethane ‘cool roof’ liquid applied waterproofing system that reflects up to 90% of the sun’s rays backed with a 5, 10 or 20 year product guarantee.
  • HydroFlect 5 & 10 – Acrylic ‘cool roof’ liquid applied waterproofing system that reflects up to 85% of the sun’s rays backed with a 5 or 10 year product guarantee.
  • Gaco – High solids silicone ‘cool roof’ liquid applied waterproofing system that reflects up to 83% of the sun’s rays backed with a 20 year product guarantee.
  • INCA Thermal Technology – Ceramic ‘cool roof’ liquid applied waterproofing system that dissipates up to 90% of heat backed with a 10 year product guarantee.


All our liquid applied ‘cool roof’ waterproofing systems can provide an equivalent R-Value of between 0.5 to 1.50 (m2.K/W) calculated through rational design.

Guarantees & Warranties of a ‘Cool Roof’ Thermal Liquid Applied Waterproofing Metal Roofs

MRC Group’s up to 20 year ‘Guardian’ System Warranty cuts through the myth & mystic of product guarantees and workmanship warranties issued by the construction industry.

Traditionally a product guarantee would be issued by the manufacturer and the workmanship warranty would be issued by the installer of the waterproofing system. Two separate pieces of paper, with differing length of terms and when put alongside each other, never answered the question of who will pay for the materials and works if the waterproofing system fails.

‘Guardian’ System Warranty is an unrivalled new era of warranty that covers Design, Materials, Workmanship & Maintenance. The length of term for each element matches and is issued as a single source, transferrable warranty for the life of the guarantee of the waterproofing system.

MRC Group challenges the construction industry to ensure that the workmanship warranty issued by contractors matches the length of term of the supplied thermal waterproofing system, thereby ensuring high quality installations with designed and tested ‘cool roof’ thermal waterproofing systems.