Rubber EPDM Roofing - Frequently Asked Questions

Below we have provided a listing of the most frequently asked questions arising in regard to Rubber flat roofing.

These have been refined from real user queries and we trust that their queries will help you with any such concerns you may have. Many of these queries have related articles for detailed response.

If you cannot find what you are seeking please do not hesitate to contact us.

Rubber Flat Roofing - garden pavilion

The top five questions we are asked

1 - What will the ClassicBond EPDM bond to?

ClassicBond EPDM is best bonded on to timber surfaces such as roofing grade plywood or OSB3 (Oriented Strand Board) sometimes called sterling board.  It can also be bonded to light weight concrete and other non porous surfaces such as Fibreglass and tissue faced insulation. 



Most Importantly - What Surfaces Cannot Be Bonded To?

ClassicBond EPDM can not be bonded to bitumous surfaces or remaining bitumous residue on a roof deck - such as:

  • Roofing felt

  • Asphalt

  • Liquid mastics


The EPDM will tend to draw the oils out of the bitumous material which causes the EPDM to lose its molecular structure and fail.


As such care should be taken when removing the old Bitumous roofing membrane as it may leave a residue which can damage the EPDM membrane.


Pragmatically and to ensure issue free installation RKD  recommend over boarding old roof coverings using an OSB3 recovery board or insulation boards.

2 - Can Rubber roofing sheets be joined?

Yes all RKD rubber membranes can be joined. Our joint technology offers joint bonding as strong as the original sheet and not detrimental to the waterproofing or strength capacities..


Jointing is used -

1, where the roof is bigger than the largest membrane size or

2, where it would be beneficial to install the membrane in smaller sections.


Not every roof is a nice flat rectangle, master the forming of corners, splicing etc and you can readily join sheeting to tackle your particular needs.


Roofing Kits Direct provide 3 ranges of EPDM membranes. - 

So - Can ClassicBond Rubber Sheeting be joined?​

Easily - They can be joined using splice (Seam ) tape or covertape. The important aspect to remember is that surfaces are primed as tapes will only adhere to a primed surface.

Resitrix Rubber Sheeting?


Again, they are designed to do so. Here however you will need a Heat Gun with flat nozzle and a Seam Roller, so slightly more specialist tools required. Don't be put off by this  a good seam weld is easy to observe as there will be a slight bleed on the welded edge.


Duoply EPDM Joining?

Duoply membranes have a pre-applied seam tape which makes the whole process straightforward. The seam tapes deliver 30% greater peel strength and 32% better shear strength than traditional seams.


3 - What can EPDM be laid over?

Each of our EPDM Rubber membrane roofing systems can be bonded to a range of different surfaces.


If you plan to leave your existing roof covering in place and install a new waterproof membrane over the top of it please consider the following:


  • ROT - A roof is only as good as its foundation timber work - If the existing roof deck and supporting timbers are rotten there's no way around this they  will need to be removed and replaced. OSB3 or exterior grade plywood are recommended for EPDM

  • UPGRADE INSULATION - Whilst you are renovating your roof consider a new warm deck insulation. - If the existing roof deck is good then in most cases the existing waterproof layer such as felt can be left in place. A new insulation can be bonded over the top using PU adhesive or mechanically fixed using screws and washers. Our new waterproof membrane can then be bonded to the insulation.  

Below is a tabular guide to what and when -



































Note - Our fleece backed DuoPly™ and bitumen backed RESITRIX® systems are more versatile in these circumstances . 

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4 - What is the biggest size epdm roofing sheet I can buy?

The biggest sheet size available from RKD, in each system, is as follows.

Note - All sheets can be joined where the roof size is bigger than the maximum sheet size:

ClassicBond & Shedcover 1.2mm - 15.25m x 30.5m (50ft x 100ft)
ClassicBond & Shedcover 1.5mm - 15.25m x 15.25m (50ft x 50ft)
DuoPly 2.54mm - 1.52m x 12.20m (5ft x 40ft)
RESITRIX 2.50mm - 1M x 10M (3ft 4" x 32ft 10")


The biggest EPDM one piece sheet sizes available in the Roofing Kits Direct range  come from our ClassicBond range. 


Membranes can be supplied in one continuous sheet up to -

15.25 metres x 30.5 metres in the 1.2mm thick membrane and

15.25 metres x 15.25 metres in the 1.5mm thick membrane.


RKD understand that covering your roof with a new membrane that has no onsite joins is perceived reassuring and offers piece of mind. However RKD would note that jointing technology in any of our EPDM systems comes as strong as the membrane itself.  Therefore multiple sheets joined together onsite actually offers a more practical solution - large membrane sheets do offer a handling challenge. 


In pragmatic terms, whilst 15m x 30m sheets are available, RKD believe that this will be a rare occurrence. We therefore offer to cut sheets to size for you. You can order any size you wish up 15m x 30m! 

Typical Weights are: -

1.5kg/square metre & 2kg/square metre for 1.2mm & 1.5mm thick respectively


Our Resitrix and Duoply systems  come in standard roll sizes and are designed to be joined on site. Both of these systems are re-inforced which makes them the preferred choice for big roofs 

Typical Weights:

RESITRIX 1m x 10m roll = 30kg / roll 

DuoPly 1.52m x 12.20m = 32kg / roll

5 - What is the difference between ClassicBond and Firestone EPDM?

RKD  get asked from time to time what are the differences are between the two systems. Obviously we stock ClassicBond so to offer a critique would be unprofessional. So here are some salient facts.


In essence ClassicBond and Firestone Rubbercover are the market leading brands for EPDM Rubber Roofing Membrane Systems.


ClassicBond is manufactured in the United States by Carlisle Syntec,. They are the largest producer of EPDM in the world. ClassicBond is the original EPDM  - it was first used on commercial roofs in the 1960's. Firestone was launched at a later date in the 1980's.


With its longevity ClassicBond can claim to have a proven 50 year life expectancy with many roofing instances still completely viable. It is CE marked and has a nominal thickness of 1.2mm as opposed to the thinner 1.1mm of Firestone RubberCover which is defined by EN 13956.


Both ClassicBond and Firestone Rubbercover are BBA certified and approved by the NHBC. (Obviously when installed in accordance with the manufacturers guidelines.)


ClassicBond's BBA Certificate No. is 11/4853

Firestone Rubbercover BBA Certificate No: 89/2216


Service life expectancy


The above BBA certificates record the following -

Firestone RubberCover has a service life in excess of 30 years

ClassicBond has an expected service life in excess of 35 years.

Other FAQ's

Can I install EPDM under a shallow pitched tiled roof? I need tiles to conform but am worried they will leak at this shallow pitch.

Yes you can install EPDM under a pitched tiled roof. This may be necessary on shallow pitched roofs to prevent leaks. Read More -

Do I need any special tools?

You will typically need a standard 9" roller set, mini roller and brush for applying the adhesives and primers. A Seam Roller is a useful tool for tapes and joins and the RESITRIX system will require a heat gun for joins. Read More -

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

Yes! EPDM rubber membranes are not effected by cement or lime additives making them ideal for waterproofing screed decks. Read More -

Can I install tiles or slabs on to an EPDM rubber roof?

Yes! EPDM rubber membranes are not effected by cement or lime additives making them ideal for waterproofing screed decks and use of slab supports. Read More -

How thick is the membrane?

ClassicBond and ShedCover = 1.2mm or 1.5mm RESITRIX = 2.5mm DuoPly = 2.54mm ElastaThane = 1.2mm in one coat

Can I Walk On My New Roof? I'm thinking balcony here.

Yes to an extent. EPDM is only designed to take LIGHT foot traffic during installation and for any occasional cleaning or maintenance. If you require more use than this, i.e. for a balcony, as stated, additional materials that can be laid over your EPDM for a more durable solution. Read More -

What Adhesive do I use when Bonding DuoPly EPDM?

DuoPly EPDM can be bonded with several adhesives, Waterbased, Solvent Based & PU Adhesives making it a very versatile roofing system Read More -

What is a Geotextile underlay used for in relation to an EPDM roofing?

The Geotextile underlay can be used on top of the rubber membrane to protect it from sharp objects when you plan a ballast (cover) of the membrane with pebbles for fire protection. Read More -

Is The RESITRIX Membrane Available In Different Colours?

Yes. The Resitrix System is available in the original Black as both a full bond (SKW) and partial bond SK-P Also in the new grey full bond SR. The grey RESITRIX SR membrane does have better solar reflective properties but is otherwise the same membrane under the skin.

Is The ClassicBond Membrane Available In Different Colours?

No The ClassicBond EPDM membrane is only available in a slate grey colour

Are ClassicBond, Resitrix and Duoply EPDM BBA Certified

Yes all three membranes are BBA Certified Read More -

Is there a right side up when installing ClassicBond EPDM Membranes?

Classicbond EPDM membranes are identical on both sides so there is no right or wrong side when installing. However you may sometimes find a small amount of writing printed on one side of the Rubber Membrane - so it may be wise to check and keep this side down as this will be more aesthetically pleasing to the eye

Why Are there bubbles on my new EPDM Rubber Roof?

Bubbles of air are unsightly but won't cause the membrane to fail - so that's good news. The bubbles are trapped air or moisture. These can be caused by a variety of issues which are all avoidable if the roof design is correct and the membrane is correctly installed. Read More -

Does it have to be dry to lay my rubber roof?

Simply, YES to both the weather and the substrate or deck. EPDM products will not adhere to wet or damp surfaces. Therefore it is vital that surfaces are dry in order that the adhesive & primers can make a good bond of the rubber to the roof deck. Ant trapped moisture can vaporize and in doing so negatively affect the performance and adherence of the membranes.

Which Rubber Roofing System is best for me?

RKD have five Rubber Roofing Systems available; 4 EPDM Membranes and 1 Liquid Rubber. We can recommend but of course the choice is yours dependent upon your individual circumstance. So no sales diatribe - we will give you a great overview and hopefully the answers will become clear...... Read More -