What is EPDM? EPDM stands for ethylene propylene diene monomer. It is a man-made rubber used as a roof sheet for flat roofs. EPDM comes in one seamless piece and seals rain tight. It also stands up to UV light. That makes it a strong pick for the flat roof of a canopy, garden house or veranda. In this guide we explain what EPDM is, how it works and when to choose it.
Houthandel Jan Sok in Meppel supplies EPDM as a full kit. You get the sheet, glue and finish from the same range. We supply home users, trade and builders.
What it is
EPDM is a man-made rubber roof sheet. The name refers to the three monomers that make up the rubber: ethylene, propylene and a diene. This mix makes a rubber sheet that stays soft, even in the cold. Unlike bitumen, EPDM is not bonded in strips. You lay it over the roof as one piece cut to size. There are no seams for water to enter. That is exactly what gives the sheet its name as a rain tight roof sheet.
Traits
Three traits explain why EPDM fits flat roofs of canopies and garden houses.
Seamless — the sheet is made to measure and laid in one piece. No overlaps, no welded seams, no weak spots where wet can enter.
Rain tight — EPDM seals against rain, melt water and wind driven wet. On a flat roof where water does not always drain at once, that is the key trait.
Sun proof — the sheet does not fade or crumble under sun light. That also makes EPDM fit for roofs that stay in the weather.
EPDM also stays soft in the cold and resists tearing and ozone. In practice, different figures are given for how long it lasts. People often mention 50 years or more. We do not state any precise guarantee as fact.
Uses
EPDM is most often used on flat roofs of wood garden builds. Three common spots follow.
Canopy — a free or attached canopy with a slight slope or a flat roof.
Garden house — the roof of a garden house or shed where bitumen later cracks.
Veranda — a covered seat where the roof faces weather and wind.
For all these uses the same rule applies. The base must be flat, dry and clean, often roof boards of Douglas. Read more about that base in our guide what is Douglas wood and see samples in canopy attached to house.
Plus and minus
Plus
Seamless and so almost leak proof. Sun proof and soft in the cold. Fits flat roofs where bitumen falls short. Sold as a full kit with glue and finish.
Minus
Higher buy price than bitumen. Needs a tight, dry and clean base. Laying demands care. A slipped sheet is hard to correct.
Care
EPDM needs little care. Remove leaves each year, keep the sheet clean and check the finish. That is often enough. Avoid sharp objects on the roof and do not leave snow lying too long.
Three basic rules apply during placement. The base must be dry and dust free. The glue goes on a grease free surface. The sheet is rolled out without pulling. A full step plan is in EPDM roof canopy. For the right kit see EPDM roofing and extras.
Common questions
Is EPDM better than bitumen?
For flat roofs of canopies and garden houses, EPDM is often the better pick. It is seamless, sun proof and flexible. Bitumen is cheaper but has welded seams that can leak over time.
How long does EPDM last?
EPDM lasts a long time. People often mention 50 years or more, it depends on laying, care and weather. We do not state an exact guarantee as fact.
Can I install EPDM myself?
With a good kit, dry weather and a tight base, you can lay it yourself if you are handy. Follow the step plan and work with two people.
Do I need roof boarding under EPDM?
Yes. EPDM lies on a flat, dry base, often roof boards of Douglas. The sheet follows the base, so bumps stay in view.