If you’ve ever walked across an older EPDM roof, you may have seen the membrane pulling tight around parapet walls, corners, rooflights or other upstands. This is commonly referred to as tenting.
The photos here are a good example. The membrane is no longer sitting comfortably into some of the changes in direction. In places, it is pulling away and forming wrinkles or raised areas.
It doesn’t necessarily mean the roof has failed, and it certainly doesn’t automatically mean you need a new roof. But it shouldn’t be ignored.
Why does EPDM tent?
EPDM moves throughout its life. Temperature changes cause movement, and over time the membrane can also shrink.
On a ballasted EPDM roof, the stone helps hold the main field of the membrane in place. Problems can become more noticeable around the perimeter, corners, walls, rooflights and other penetrations where the membrane is restrained.
As the membrane pulls, stress can build at these points. Instead of remaining tight into the change of direction, it starts to bridge or “tent.”
The important thing isn’t just seeing the tenting. It’s checking what that movement is doing to the rest of the roof.
Are seams being pulled? Are patches starting to lift? Is the membrane pulling away from an upstand? Are corners under stress? Has the membrane actually split anywhere?
Those are the things I would be looking for.
EPDM tenting at a parapet corner where membrane movement has created visible stress at the change in direction.
Can EPDM tenting be repaired?
Yes, in many cases it can.
If the tenting is limited to a few areas and the rest of the roof is still in reasonable condition, targeted repairs may be the sensible option.
Depending on the location and condition, that can involve releasing the stressed membrane, allowing it to relax, re-securing the membrane correctly and installing new compatible EPDM membrane or flashing where required.
The exact repair will depend on what you’re dealing with. A small problem around one penetration is very different from membrane movement running along hundreds of feet of perimeter.
When does it become a bigger problem?
This is where I wouldn’t make a blanket recommendation.
If I found two or three isolated areas of tenting on an otherwise serviceable roof, I wouldn’t recommend replacing an entire roof simply because of them.
If I’m seeing it repeatedly around the building, around numerous penetrations and at long sections of perimeter, then it’s a different conversation.
At that point you have to consider the age of the roof, condition of the membrane, seams, previous repairs, insulation, evidence of moisture and the cost of continually repairing individual areas.
Eventually there comes a point where spending more money repairing an ageing roof doesn’t make financial sense.
What are the options?
| Option | When it may make sense | Pros | Cons |
|---|---|---|---|
| Monitor | Minor tenting with no immediate signs of failure | No unnecessary work | Needs regular inspection |
| Local repairs | A few isolated areas | Extends service life without replacing the roof | Doesn’t address movement elsewhere |
| Larger targeted repairs | Several affected areas but roof otherwise serviceable | Can deal with the worst areas and buy useful time | Cost starts increasing on widespread problems |
| Re-roofing | Widespread tenting combined with ageing membrane, seam failures, moisture or numerous previous repairs | Deals with the roof as a complete system | Highest initial cost |
Does tenting mean the roof needs replacing?
No.
That’s probably the most important point.
Tenting is a symptom that needs investigating, not an automatic reason to condemn an EPDM roof.
I’ve seen roofs where a few targeted repairs are perfectly reasonable, and I’ve seen others where the amount of movement and general condition of the roof means continuing to patch it simply doesn’t make sense.
The decision should be based on the whole roof, not one wrinkle in the membrane.
Tenting around a skylight curb showing how EPDM movement can affect roof penetrations as well as perimeter walls.
What to look for
If you have a ballasted EPDM roof, pay particular attention to the membrane around parapets, corners, rooflights, curbs and other penetrations.
If the membrane looks as though it’s being stretched across a corner rather than sitting naturally into it, or you’re starting to see seams and previous repairs being pulled, it’s worth having it looked at.
Catching these areas before the membrane tears or a seam opens can make the difference between a relatively straightforward repair and a much bigger problem.
Frequently Asked Questions
How quickly does EPDM tenting get worse?
There’s no fixed timeframe. Some areas may remain relatively stable for years, while others can continue moving and start putting more pressure on seams and flashing details. That’s why monitoring the affected areas is important.
Can you repair just one section of a ballasted EPDM roof?
Yes. One advantage of this type of roof is that the ballast can be moved aside to expose the membrane. If the problem is localised and the surrounding roof is still in reasonable condition, a targeted repair may be possible.
Why does tenting often show up around parapets and roof curbs?
These are areas where the membrane changes direction and is restrained. As the membrane moves over time, these locations can become points where that movement and stress are much more visible.
Can tenting cause an EPDM seam to open?
It can contribute to it. If enough tension develops in the membrane, that stress can be transferred to nearby seams, patches and flashing details.
Is EPDM tenting something that should be checked every year?
If tenting has already been identified, I would certainly include those areas in future roof inspections. Photographs are useful because they allow you to compare the same locations over time and see whether the movement is getting worse.
About Peter Coscolin
