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If you plan to leave your existing roof covering in place and install a new waterproof membrane over the top, you will need to consider the following:

ROT - If the existing roof deck and supporting timbers are rotten these will need to be removed and replaced. OSB3 or exterior grade plywood are both good deck materials for bonding the new waterproof membrane.

UPGRADE INSULATION - Whilst you are carrying out work on your roof, it might be a good time to install new warm deck insulation. If the existing roof deck is in good order then in most cases the existing waterproof layer (such as felt) can be left in place. If you are deciding to insulate on top of the existing waterproof layer, you must bond the new insulation on the top using PU adhesive or mechanically fixed using screws and washers. The new waterproof membrane can then be bonded to the insulation.  

We have listed below the preferred bonding surface for each of our EPDM systems along with the most appropriate adhesive. You will notice that the fleece-backed ClassicBond Pro and bitumen-backed Resitrix systems are more versatile. This is not an exhaustive list so if you don't find what you are looking for give us a call and we will do our best to help!

ClassicBond® & Skyguard System

Non-reinforced EPDM

N.B. Upstands and perimeter are always bonded with a contact bonding adhesive or spray contact

ClassicBond Pro™ System

Fleece Backing

N.B. Upstands and perimeter are always bonded with a contact bonding adhesive or spray contact

RESITRIX® System

Self-Adhesive Bitumen Compatible

N.B. Upstands and perimeter are bonded in the same way using FG35 Primer

Whilst bubbles or blisters on a one-piece EPDM roof can be unsightly, they will not cause the rubber membrane to fail. These bubbles of trapped air/moisture can be caused by a variety of issues which are all avoidable if the roof design is correct and the membrane is correctly installed.

This article explains the causes of the most common bubbles and blisters that could appear on EPDM.

Vapour From Contact Bonding Adhesive

Contact bonding adhesive is used for bonding the rubber membrane on upstands and around the perimeter of the roof deck. The adhesive is solvent-based and must be allowed to gas off and become touch dry prior to bonding the membrane into position. If the rubber is bonded prior to the adhesive drying, then bubbles will appear under the membrane caused by the trapped vapour from the adhesive.

These bubbles are often not severe and will disappear over a relatively short period of time as the EPDM membrane is partially breathable. The process can often be accelerated by weighting the affected area. In severe cases where the adhesive has not been allowed to become touch dry, the membrane may need to be peeled back and re-bonded. 

Expanding Trapped Air Within The Roof Structure

This type of bubbling/lifting can occur on warm deck roof designs where the EPDM membrane is fully bonded onto either a timber deck or directly onto the insulation. If the roof structure under the insulation is damp or the boards are fitted with large gaps the trapped moist air will expand when the sun warms the roof and appear along the seams in the boards. Often the membrane will contract back into position in the evening when the roof cools back down. 

It is important when installing the warm deck insulation to ensure the roof structure underneath is dry and that the insulation boards are fitted snuggly together. Any gaps can be filled with an expanding foam adhesive to stop the trapped air from lifting the membrane. If you are installing a timber deck over the insulation a cheap Visqueen membrane can be installed under the timber deck, this is also a great way of ensuring that the expanding air doesn't cause the membrane to lift.

All of our roofing systems are designed to take foot traffic and will withstand access to the roof for window cleaning and general maintenance  The EPDM systems can be walked on both during and after installation, EPDM is designed to take LIGHT foot traffic for occasional cleaning or maintenance. However, common sense needs to be applied. Avoid studded boots and shoes. If you intend to use a ladder on the roof, use a plank or board to spread the load.

The Resitrix System can withstand a higher level of traffic and is suitable for escape routes. The membrane is reinforced and thicker than standard EPDM. RESITRIX also has a textured surface for slip resistance.  

If you wish to use your rooftop as a balcony or sun deck then there are several additional options available to you.  

1. Install Promenade tiles/decking straight onto the EPDM membrane. 
   Rubber Promenade Balcony Tiles 500mm x 500mm x 30mm
   

2. Use slab supports to install slabs over the membrane. 
   Paving Slab Support

3. Cover the membrane with a 50mm concrete screed and then proceed to lay tiles/slabs over the top. 

If you would like more information about concrete screed and EPDM rubber membranes, please check out the below article.

Can I install a cement screed on top of EPDM rubber membranes?

ClassicBond Pro EPDM membrane is incredibly versatile and can be bonded to almost all existing flat roof materials including bitumen-based products such as torch-on felt, asphalt and liquid mastics. ClassicBond Pro EPDM roofing membrane is a polyester reinforced elastomeric flat roofing membrane that consists of an EPDM laminated to a polyester reinforcement layer.

Install ClassicBond Pro over the following surfaces…

• Timber
• Tissue Faced Insulation
• Glass Fibre
• Felt
• Asphalt
• & Many More

The fleece reinforcement offers protection from the oils in bituminous products that would normally damage EPDM rubber and improves puncture resistance meaning that flat roofs can be repaired without removing the existing roof. That said roofs that have suffered water damage and show signs of rot must be removed and replaced with new materials.

ClassicBond Pro EPDM has a greater range of adhesives that can be used to bond the membrane in place. This article will give the advantages of each adhesive that is compatible with ClassicBond Pro.

Sprayable Contact Spray Adhesive

Sprayable Contact Bonding Adhesive is a spray-applied, high-strength adhesive, formulated especially for gun application.  This product is perfect for attaching the membrane to upstands and detailing. The great thing about this product is that it can be used straight out of the box and due to its spray application it means drying and installation time is dramatically reduced. 

Below is a quick overview of the flat roofing systems we have available with links giving more product information, pricing, and installation tips. You'll also find some additional resources that will help you on your journey of working out which is the best system for you.

Our Roofing Solutions

We have five different roofing solutions for you to choose from:

• The One-Piece ClassicBond system is our most popular EPDM and is ideal for small to medium-sized flat roofs up to 100m2. This system offers good value for money, a 50-year life expectancy and is the preferred choice due to its ease of installation and the fact that most roofs will be installed in one piece without the need for any joins.
• The Resitrix Self Adhesive EPDM system is perfect for larger commercial flat roofs & gutter lining. This is heat welded, reinforced membrane that is ideal for overlaying existing roofing often without the need to strip back.
• The ClassicBond Pro Fleece Reinforced Membrane is also ideal for larger roofs where ClassicBond may not be an option. This is a cold-applied system and is popular due to the speed of installation.
• The Arboflex Waterproofing system is a no-nonsense polyurethane liquid roofing system that can be used straight out of the tin. This product is perfect for complicated roofs and can be applied straight over most roofing substrates.
• Skyguard is our most cost-effective roofing system and is designed specifically for outbuildings and sheds etc. This product is quick and easy to install and has a 50-year life expectancy.

Additional Information about our Roofing Systems

• Roofing Systems Comparison
• View our range of FAQs

Depending on the design of your roof and the available pitch angle, it may not be possible to use traditional roof tiles. Some modern interlocking roof tiles will accommodate a pitch angle as low as 15 degrees, whereas more traditional Rosemary or Victoria tiles require a 35-degree pitch minimum. If you have an existing tiled roof that is leaking due to water blowing up under the tiles then a good solution is to replace the tiles with an EPDM rubber membrane. 

Installing an EPDM rubber membrane is a relatively straightforward process. Start by instaling a timber deck onto the existing rafters so that the rubber membrane can be bonded into place and finished off with the correct edge trims. It is important to ensure the roof structure has ventilation if the roof has traditional mineral wool installation in between the rafters. 

If your roof pitch is too shallow for the choice of tile, but you still want the look of a tiled roof, then it is possible to install the tiles over a rubber membrane on counter battens. Check out our other roof tile article for more information. 

There are two types of Rubber. Synthetic, which is used to make products such as EPDM roofing membranes, butyl pond liners and window seals. The second type is natural rubber also known as India rubber. Natural rubber derived from latex is used by many manufacturing companies for the production of a variety of rubber products including shock mounts, gaskets hoses and tubing where carbon black is added to improve its strength. Currently, rubber is harvested mainly in the form of latex from certain trees. The latex is a sticky, milky colloid drawn off by making incisions into the bark and collecting the fluid in vessels. The latex then is refined into rubber ready for commercial processing. Natural rubber is used extensively in many applications and products, either alone or in combination with other materials.

The Geotextile fleece membrane can be used in a number of ways:

1. The Geotextile can be used on top of the rubber membrane to protect it from sharp objects when it is planned to ballast (cover) the membrane with pebbles for fire protection.
2. Where a cement screed is being installed on top of the rubber membrane to provide a hard-wearing surface for slabs or tiles the geotextile can be placed on top of the EPDM to protect it from sharps in the screed.
3. Install the Geotextile fleece directly over the current roofing substrate to help protect the new rubber membrane from any sharps that could puncture the membrane. In this scenario, the rubber membrane cannot be glued in place so it is either secured using Russ strips (A Grid of mechanically fixed bonding strips) or ballasted in position with pebbles or a green roof. This method is only applicable to ClassicBond.

CLASSICBOND® and Firestone Rubbercover are the leading brands for EPDM roofing membrane systems. We often get asked what are the differences between the two systems. 

CLASSICBOND® is manufactured in the USA by Carlisle Syntec, the largest producer of EPDM in the world. CLASSICBOND® is the original EPDM which was first used on commercial roofs in the 1960s whereas Firestone was launched much later in the 1980s. For this reason, CLASSICBOND® is the only EPDM brand that can truly claim to have a proven 50-year life expectancy.

CLASSICBOND® EPDM is CE marked with a nominal thickness of 1.2mm as opposed to the thinner 1.1mm of Firestone RubberCover as defined by EN 13956.

CLASSICBOND® BBA Certificate No: Certificate No: 11/4853

FIRESTONE RUBBERCOVER BBA Certificate No: 89/2216

Both CLASSICBOND® and Firestone Rubbercover are BBA certified and approved by the NHBC when installed in accordance with the manufacturer's guidelines. The BBA certificates state that Firestone RubberCover has a service life in excess of 30 years and CLASSICBOND® has an expected service life in excess of 35 years.

Installing traditional tiles over a rubber membrane

The pitch angle of your roof will determine what type and design of the tile can be installed. Some modern interlocking roof tiles will accommodate a pitch angle as low as 15 degrees, whereas more traditional Rosemary or Victoria tiles require a 35-degree pitch minimum.

In this example, the client needed to install a traditional tile on a roof where the pitch was too low for the tile 

EPDM membranes can be installed on any pitch of roof. However, in certain circumstances, it might be important for the roof to have a tiled finish. In the following steps, we will show how a roof can be waterproofed using an EPDM membrane and then have a decorative tile overlayed on counter battens to give the desired finish.

Yes. ClassicBond Pro EPDM (formally known as Duo-Ply) holds the British Board of Agrément certificate, No. 11/4853, issued to Flex-R Ltd. The BBA carries out assessment, testing, approval and certification of products and systems for the construction industry against national requirements, internationally recognized standards or other relevant technical specifications, reviewed and reissued every 3 years.

The fire ratings range in accordance with the build-up of the roof.

As stated in the BBA certificate No.02/3967 ClassicBond Pro Fleece reinforced EPDM (formally known as Duo-Ply) has a rating of Ext FAA as per BBA certificate. This relates to the following roof construction of steel deck, vapour barrier, PIR/PUR insulation and ClassicBond Pro Fleece reinforced (formally known as Duo-Ply). Tested in accordance with BS476 -3

The above build-up is mainly for commercial-type properties so the ratings would be misguiding for domestic-type buildings. In 2005 we ran further tests on typical residential style roofs and the following ratings were achieved.

Ext FAC Typical warm roof construction; OSB deck, vapour barrier, insulation and ClassicBond Pro Fleece Reinforced (formally known as Duo-Ply).

Ext FBC Typical cold roof construction; ClassicBond Pro Fleece Reinforced (formally known as Duo-Ply).

Test to BS476 – 3: 2004 External Fire Exposure test

• BBA Certificate
• Fire Certificate

What Is The Correct Adhesive For My Roof Deck

In this article, we will look at what roof deck surfaces CLASSICBOND EPDM can and cannot be bonded to and also the correct adhesives for the various roof surfaces that you might want to waterproof. 

This article is not intended as a definitive list so please contact us for further advice if you do not find the answer you are looking for. 

What Surfaces Can I Bond ClassicBond EPDM To?

ClassicBond EPDM is best bonded onto timber surfaces such as roofing grade plywood or OSB3 (Oriented Strand Board) sometimes called sterling board.  

ClassicBond can also be bonded to lightweight concrete and other non-porous surfaces such as Fibreglass and tissue faced insulation. 

What Surfaces Can Not Be Bonded To?

ClassicBond EPDM can not be bonded to bituminous surfaces such as:

• Roofing felt
• Asphalt
• Liquid mastics

The EPDM will tend to draw the oils out of the bituminous material which causes the EPDM to lose its molecular structure and fail. Care should be taken when removing the old Bituminous roofing membrane as it may leave a residue that can damage the EPDM membrane. We normally recommend over boarding old roof coverings using an OSB3 recovery board or insulation boards.

EPDM membranes require the substrate to be dry prior to installation so that the adhesive & primers can effectively bond the rubber to the roof deck. EPDM products will not adhere to wet or damp surfaces. It is important to bear in mind that trapped moisture within the deck may vaporise and negatively affect the performance of the membrane. 

If you would like more tips on when to install your EPDM roofing, check out the video below.

Yes. The Resitrix System holds the British Board of Agrément certificate, No. 06/4329 issued to Carlisle Construction Materials GmbH. The BBA carries out assessment, testing, approval and certification of products and systems for the construction industry against national requirements, internationally recognised standards or other relevant technical specifications, reviewed and re-issued every 3 years.

The Resitrix System Is Also Fire Rated

Fire behaviour to DIN 4102, Part 1 B 2 B 2
Reaction to fire to DIN EN 13501, Part 1 Class E
Fire behaviour to DIN 4102, Part 7, and DIN EN 1187 resistant to flying sparks and radiating heat
Fire Tests on Building Materials and Structures according to BS 476 Part 3 “External Fire Exposure Roof Test” - Resistant to fire

What Was The First Use Of Natural Rubber?

Rubber was first discovered by Joseph Priestley of England in 1770, best known for his discovery of oxygen, he found that pencil marks could be “rubbed out” by the substance. From this early use, rubber derived its name. It is now thought that 25 million tonnes of rubber is produced per year.

When Was Rubber First Used On A Roof?

EPDM Rubber unlike Butyl rubber is completely UV and infrared stable, making it perfect as a roofing material. The first commercial rubber roof was installed in the United States in 1965 by Carlisle Syntec, it is now 50 years old and still going strong. This makes Classicbond the only EPDM with a proven 50-year life expectancy! 

Classicbond EPDM membranes are identical on both sides so there is no right or wrong side when installing this product. It is important to bear in mind that sometimes there may be a small amount of manufacturer writing printed on one side of the rubber membrane; if this is the case we recommend installing this side down onto the deck so that the clear side is only visible.