EPDM membrane
- Large single sheets reduce the number of joints
- Flexible, and able to accommodate some building movement
- Detailing at edges and penetrations must be precise
- Less suited to roofs with many corners or heavy use
Roofing
EPDM Rubber Roofing for Flat Roofs
EPDM is a synthetic rubber membrane, usually supplied in large sheets, that can cover wide flat roofs with relatively few joints. It is a practical option for many domestic flat roofs, and it is worth understanding how it works before comparing proposals.
The material
What EPDM is
EPDM stands for ethylene propylene diene monomer, a synthetic rubber. It is manufactured as a flexible sheet that stays pliable over a wide temperature range, which allows it to move slightly with the building. The sheet is most often black, although lighter finishes are available, and it is usually laid in a single piece over the roof where the size allows.
The membrane is fixed or bonded to a prepared deck, then sealed at its edges and at upstands (raised edges where the roof meets a wall) with trims and adhesives. Because it comes in large sheets, the number of joints is reduced, but the detailing at edges, outlets and penetrations matters just as much as the main area of the roof.
When EPDM may suit a flat roof
EPDM tends to suit larger flat areas, such as extensions, rear additions and some garages, where a continuous sheet can reduce the number of seams. It can also be a sensible choice where the roof is simple in shape and has a manageable number of pipes or vents that can be sealed neatly.
It is less suitable where the roof has many corners, complex upstands or heavy foot traffic. These features can be managed, but they increase the number of details to get right. A survey will help confirm whether EPDM is the most appropriate membrane for your roof.
Early warnings
Signs your EPDM roof needs attention
Rubber membranes age slowly, but they can be damaged by ponding water, punctures, failed seals and poor drainage.
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Splits or punctures
Splits, tears or punctures can let water through the membrane. They are often found near edges, outlets or fixings, where the sheet is under the most stress.
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Ponding water
Water that sits on the roof after rain can slowly degrade the membrane and encourage growth. It usually points to a fall that has been lost or a blocked outlet.
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Failed edge seals
Edge trims and adhesive seals can lift over time. Gaps at the perimeter are a common route for water beneath the membrane.
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Leaks at the ceiling
Damp or staining below the roof can point to a leak in the membrane or in a penetration, such as a vent or pipe seal.
Preparation
What the survey checks on an EPDM roof
A good installation starts with an honest look at the roof beneath the membrane.
- The condition and dryness of the deck, including any soft or split boards
- The falls, and whether water reaches the outlets without standing
- The position and sealing of pipes, vents and roof lights
- The height, condition and fixing of upstands and edge trims
- Any previous coverings, and whether they can be removed or overlaid
- Access, protection needs and the sequence of work
- Whether any change to the roof needs Building Regulations approval
The process
How an EPDM roof is installed
The steps below describe a typical installation. The exact method depends on the deck and the manufacturer’s instructions for the system.
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Preparing the deck
Old coverings are removed where practical, and the deck is repaired, cleaned and checked for dryness. Sharp edges or protrusions are dealt with so they cannot puncture the membrane.
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Priming and falls
Primer is applied to the surfaces that will receive adhesive, and falls are formed or checked to direct water towards the outlets.
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Laying the sheet
The membrane is unrolled, positioned and allowed to settle. It is then fixed or bonded to the deck, with laps and edges aligned.
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Sealing and trims
Joins are sealed with approved tapes or adhesives, and perimeter trims and upstands are fitted. Pipe collars and other penetrations are sealed around the pipe.
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Inspection and handover
We check the seals, joints and edges, test for any loose areas, and explain how to look after the roof. Written information about the system is provided.
Next step
Ask about EPDM for your flat roof
We can look at your roof, explain whether EPDM is a suitable choice, and compare it with other flat roof systems. You receive the findings and the proposed work in writing.
Comparing systems
EPDM and other flat roof systems
Each flat roof system has its strengths. The right one depends on the roof shape, the use of the space below and the detailing needed.
Felt and GRP systems
- Felt is built up in layers and often suits existing felt roofs
- GRP forms a seamless laminate, often on smaller shapes
- Both depend heavily on the deck and the drainage
- The most suitable option is confirmed by the survey
Keeping the details under control
Most of the work on an EPDM roof is in the details. The membrane is only as good as the edges, the outlets and the joints around pipes and roof lights. These areas need sealing with materials that suit the membrane, and they must allow for movement without pulling the sheet tight. We pay close attention to them during the survey, and we explain which details we would expect to be renewed and which can be kept.
Surface traffic is worth thinking about too. Equipment left on an EPDM roof, or repeated trips across it, can wear or puncture the membrane. If the roof is to carry anything, such as a satellite dish, a condenser unit or a rooftop fixing, tell us in advance so that the fixings and protection can be planned as part of the work.
Questions
EPDM roof questions
Common questions about rubber flat roofs, answered in plain terms.
Is EPDM only available in black?
Black is the most common finish, but lighter and reflective finishes are available in some systems. Colour can affect surface temperature, so we discuss the options as part of the survey.
Can EPDM be laid over an old felt roof?
Sometimes, if the existing layer is sound, flat enough and suitable as a base. Overlaying is not always appropriate, and in many cases the old layers should be removed. We explain which applies to your roof.
How long does EPDM last?
A well-installed membrane can perform for many years, but its life depends on the deck, the detailing and the maintenance. We cannot give a fixed lifespan for any roof.
What causes most EPDM leaks?
Leaks often start at penetrations, edges and joins rather than in the middle of the membrane. Failed seals, poor falls and punctures from debris or sharp objects are typical causes. A survey can identify which of these applies.
Can I repair a small puncture myself?
Please do not attempt repairs yourself, and do not walk on the roof to look for the fault. A small fault can become serious if it is left, and a professional can check the membrane safely and advise on the right repair method.
Where we work
Roofers serving five regional areas
We work across five regional areas: North London, North West London, West London, Hertfordshire, Buckinghamshire. Not sure if we cover your street? Call us on 01632 960123, or see all areas we cover.
Next step
Book a flat roof assessment
If your flat roof is due a check, or you are considering EPDM, get in touch through the contact page to arrange a visit.