EPDM vs. GRP Roofing, which one would you choose?

Do you have the problem of not knowing which type of flat roof to have installed on your house? I will admit it can be a very difficult decision to make with all the various types of roofing systems on the market. Your roof is probably one of the most important parts of your building and can cost you a fortune in damages if and when it fails. Here we look at EPDM vs. GRP Roofing, and try to help you with your decision on which one to choose for your home.

EPDM (Ethylene Propylene Diene Monomer) and GRP (Glass Reinforced Polyester) roofing are both good choices for flat roofs, as long as they are installed correctly, by a well trained and experienced flat roofer. It is really a matter of preference when choosing between the two. At Hartseal we believe that GRP roofing offers you a better solution for your flat roof, so much so that we have built our whole company around this revolutionary product.

EPDM-colied-rubber-rollEPDM roofing is a type of rubber that comes on a roll (like a carpet) and available in various sizes. During the installation process the contractor rolls it out over your roof using similar methods to a carpet fitter and then carefully cuts it to the shape of the roof – when applied properly, it has an excellent finish. I can forsee two problems with this product, one being on larger roofs where you can’t get the right size to cover the whole roof so there has to be a joint in the roof where they overlap the two rolls and glue them together, GRP roofs on the other and are completely seamless with no joints and this ensures that water can’t get in. The other problem I have with EPDM roofs is that it seems like having a vinyl mat (similar to the rubber you would use in your kitchen or bathroom) on the roof. Furthermore, I have done extensive research on the matter where I have seen comments made by EPDM installers with regards to squirrels and birds pecking away or eating the roof. EPDM comes in different thicknesses so if you should choose to go with an EPDM roof make sure you go with the thickest one you can find. Click here to see a video of a leaking EPDM roof, the comment regarding the issue are in the comment section below the video.

GRP is a hard plastic material which would never fail due to an animal pecking at it. It is extremely tough and can be used in heavy traffic walkways if installed with a non slip coating. The only concern with GRP roofing is that it has been known to crack due to expansion and contraction of the roof. We believe this takes place when ply is used instead of OSB boards for the decking surface below the GRP membrane, OSB boards are tong and grooved which ensures that the deck is completely flat, the boards are fitted tightly together which allows for minimal movement which could easily cause cracking to take place. I like to think a GRP roof is like having a boat on top of my roof (there is a very good reason why boats are made from GRP and not from EPDM). If you should choose to have Hartseal install your flat roof you can sleep easy, knowing that our roofs come with a 25 year Topseal Guarantee.

I hope this has been useful to you and will hopefully help you with your difficult choice on what type of flat roof to go for. EPDM vs GRP Roofing – only you can decide which is best for you, but I know exactly which one I would choose. If you would like to find out more then click here to see a builders forum for a  discussion by flat roofers regarding this topic.

Please don’t forget to leave a comment in the box below, it would be great to hear your views.


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  1. Brendan Coates 08/06/2010 at 1:28 pm #

    Thanks for the interesting article, I have been thinking about EPDM. I have also noticed that people have commented about birds picking holes in it. A GRP roof definatly sounds like a better idea. Thank you Hartseal.

  2. Ryan 08/06/2010 at 1:36 pm #

    Thanks for the comment Brendan, I would recommend that anyone who chooses to have an EPDM roof installed to go for one of the thicker options. I am biased but completely agree that GRP is a much better solution for your roof. Please fill out your details in the contact box for a free quotation.

  3. ceri morgan 16/08/2010 at 9:28 pm #

    i would like an estimate please for grp roof, 7 meters by 3 meters, ‘warm construction’. thanks

  4. admin 18/08/2010 at 1:29 pm #

    Hi Ceri, Unfortunately it is very hard to give an estimate without knowing a bit more about the job, please email us some pictures of the roof.

  5. Rob McC 06/11/2012 at 1:15 pm #

    How many layers of glass fibre are used? From the video it appears there is just one plus the narrow bandage strips over the joints. (GRP in boats have many layers built up).

  6. Ryan 06/11/2012 at 4:59 pm #

    Hi Rob,

    The whole deck is covered in fibreglass matting. A boat is constructed using a completely different process compared to the way we lay a roof. Our BBA approved system is made up of three levels.
    1. The OSB 3 boarding provides the strength
    2. The fibreglass matting and resin provides the waterproofing
    3. The top coat provides the resistance to UV rays from the sun

    I hope this helps. Please feel free to contact us should you have any other questions.

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