How to choose and apply a rubber roofing coating

Rubber roofing does not need to be difficult. Get the right rubber roofing material and apply it properly to enjoy long term durability, great UV stability, much needed flexibility and the reliable protection flat roofs need to remain waterproof for years.

How to select a rubber roof coating that fits your project

Know your roof and budget. Here's 7 questions to ask your rubber roofing project:

  • Do I need a primer? Metal substrates shouldn't need priming. Porous substrates such as felt and bitumen flat roofs generally do, so be sure to factor this in to cost.
  • How does the rubber cure? In other words, how and when does the coating harden into a membrane? This will affect when you can apply it and how much prep you need to do. For example, is there a catalyst that needs to be mixed in and how long does that take to work?
  • What's my budget? Do I want greater durability or is my cost per meter more key?
  • Is the coating flexible enough? Buildings move, particularly in extreme temperatures. Will the coating (both primer and topcoat) move with it or be forced to tear?
  • What's the best way for me to apply it? Usually by brush, roller or spray. Brush and roller are great for most projects and are easy to prepare for. Spraying is perfect for making big projects more manageable, but there's more prep involved.  
  • Do I need to use reinforcing matting? Some coatings require this throughout the roof, while others just need upstands and details reinforced. You may also want to reinforce seams for added protection.
  • Is my coating UV resistant enough? Everyday, roofs take on relentless UV rays and this can degrade lower quality coatings, causing leaks that can be difficult to track down. 

How to apply the rubber roofing coating

The quickest, easiest and most effective way.

Measure your new rubber roof

First off, how big is the roof? Take into account upstands and details. You'll need this and the coating's coverage rate to work out how many litres/gallons/kgs you'll need. A typical coverage rate is 1.8kg/sqm, so if a roof is 20 sqm you'll need 36kg. Apply the right amount, and this is also a easy and reliable way of ensuring the correct coverage. 

Rubber roofing vs. flashing, trims and details

What to do where the rubber meets the flashing or edge trims?

This varies with each coating. Most recommend lifting any led flashing, where possible, and running the coating underneath. If not, a combination of a primer, reinforcing matting and butyl tape could be used. 

Where trim protects the edges of a flat roof, use butyl tape to cover these, ensuring both the ends of the flat roof, and the beginning of the trim are covered. This means that the rubber coating can form a seamless barrier.

Details may need further waterproofing with reinforcing matting, usually sandwiched between two layers of coating. Rubbers tend to be too sticky for glassmatt, so other reinforcing mattings are used.

Rubber roofing detail protection

Preparing your rubber roofing material

Step one is to clean. A well prepared surface can mean the difference between a repair lasting 15 years or 5 years. Once this is done, you're ready to prepare the rubber. We recommend using Iso A Clean to disinfect the surface.

How liquid rubber becomes a roof membrane

A coating starts life as a liquid, which needs at least two things to cure into a durable and waterproof membrane: a catalyst to begin the cure, and the correct temperature for a sustained length of time. With the advanced coatings on the market today, this is usually not an issue. For example a moisture cured rubber can cure in as little as 1ºC in just a few hours. 

How to apply with brush or roller

It's a good idea to place each tin with a corresponding section of roof. For example, if one tin does 5 sqm, place that tin within a marked off area of 5 sqm. This means that the correct coverage is easier to achieve, and that you're not going to run out of coating. It's also a good idea to mark the tins that have had the catalyst added, to avoid confusion. This is where it's important to know your working time. Coatings with a slow cure are happy to be catalysed and then sit in the tin for a little while, meaning you could catalyse a few tins at a time. Other coatings may cure much faster, so only one tin can be cured at a time, or else you end up with a tin of solid rubber.

Easiest way to roller on is to pour the liquid in a line over the area, and then spread evenly with a short haired roller. Check out the video below: 

How to apply a liquid rubber with a spraying machine

First, ensure you have the correct sized spraying machine. Thicker rubbers require a larger machine, and different rubbers may need varying amounts of thinners to make spraying easier. 

You also need to take tip size and hose length into account. It's easier than it sounds. Get in touch to get some advice on your project. 

Rubber roofing that we recommend

We've spent years building up a range of advanced roof coatings that tick all the boxes above. This gives you access to the latest, most durable and easy to apply roof coatings, all tried and tested after years of research. 

HyperCoat rubber from ISO Paint

Tough, reliable and with an impressively low cost per meter, HyperCoat is a popular choice for roofing contractors. 

  • Excellent adhesion to almost any surface, particularly when paired with the HyperCoat primer
  • Brilliant weather and UV resistance, resulting in long term protection
  • No primer needed on wood or concrete
  • Remains elastic in temperatures as low as -40ºC 
  • High tensile and tear strength, meaning the membrane remains durable where others tear
  • Good chemical resistance
  • Breathable, so humidity does not build up under coat

Liquid Rubber EPDM from ProGuard Coatings

ProGuard are the only company to have achieved turning EPDM into a coating, and the benefits are well worth the years of research. 

  • Hydrophobic material, so waterproofs the roof instantly
  • Ponding water guarantee, perfect for flat roof repair
  • One coat system, meaning less material cost and time spent on site
  • Straight on metal, unlike other coatings, making big industrial projects quicker
  • Corrosion stopper, so great for treating cut edge corrosion 
  • Great flexibility and UV resistance, giving long term protection
  • Highly versatile, can be used on many different substrates

Moisture Cure Rubber from ProGuard Coatings

 Similar durability as EPDM Liquid Rubber, but with a significant British weather twist

  • Apply in temperatures as low as 1ºC, great for colder times of the year
  • Cures in just 1-3 hours by absorbing moisture from the air, so impending bad weather is not an issue
  • Withstands ponding water, ideal for flat roof repair
  • Easy to spray, even without diluting, unlike other coatings of this durability
  • Chemical resistant and UV stable after just one coating
  • Also available as a clear version, SuperArmour, great for skylights and various preservation projects

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