Wrong Products Used for EPDM Roof Repairs: When a Quick Fix Becomes the Problem

EPDM is a very repairable roofing system when the right materials and preparation are used.

Unfortunately, one of the things I regularly come across when inspecting older EPDM roofs is previous repair work carried out using products that were never really suitable for the membrane in the first place.

Usually, it starts with a leak.

Someone finds an area they think may be causing the problem and applies a sealant, mastic, coating or patch over it. It may stop the leak temporarily, so as far as everyone is concerned, the problem has been solved.

A few years later that repair starts cracking, peeling or separating. Another product gets applied over the top. Then perhaps another repair is added later.

Eventually, you end up with what you can see in these photos.

These are from a ballasted EPDM roof I inspected in Richmond, BC. There are several areas where different repair materials have been applied to the membrane over the years. Some are deteriorating, some are separating, and in places it becomes difficult to determine exactly what the original problem was.

Heavy sealant has been used around this curb detail rather than carrying out a proper EPDM membrane repair.

Why does the right repair product matter on EPDM?

EPDM is a synthetic rubber roofing membrane, and repairs need to be carried out using products and methods that are compatible with the existing membrane.

That sounds obvious, but it doesn’t always happen.

General-purpose roofing mastics, incompatible sealants and coatings can behave very differently from EPDM as the roof moves and temperatures change.

A flat roof doesn’t stay completely still. The membrane, insulation, deck, flashings and other components all respond to temperature and building movement.

A repair needs to cope with that movement.

If it can’t, it can eventually crack, split, lose adhesion or peel away from the membrane.

The problem with repairing the repair

This is where things can start getting messy.

If an old repair begins failing, simply covering it with another layer of sealant doesn’t necessarily solve the underlying problem.

You may now have a new material relying on an old material that is already losing adhesion.

Then another repair gets added.

And another.

Eventually, rather than repairing the original EPDM membrane, you’re trying to make new products stick to several layers of old repair material.

I’ve seen this plenty of times on older roofs.

It doesn’t automatically mean the entire roof is finished, but it does make a proper repair more involved.

What should an EPDM repair look like?

There isn’t one repair detail that covers every situation.

It depends on what has failed, where it is located and the condition of the surrounding membrane.

Generally, however, a proper repair starts by getting back to a surface that can actually be repaired.

That may mean removing failed sealants, coatings and previous patching material.

The EPDM then needs to be properly cleaned and prepared before a compatible EPDM repair system is installed.

Depending on the problem, that could involve EPDM flashing materials, cover tape, uncured flashing, primer, compatible adhesives or sealants specified for use with that membrane system.

The important point is that the repair should become part of the roofing system rather than simply being something smeared over the top of it.

This previous repair material had never properly bonded to the EPDM membrane and could simply be lifted away by hand.

Can the old repair material just be removed?

Sometimes, yes.

Other times, it isn’t that simple.

If the material has been sitting on the roof for years, removing it without damaging the EPDM underneath can take considerable care.

You also don’t necessarily know what you’re going to find until the old repair is removed.

The original membrane may still be perfectly serviceable underneath.

Alternatively, the EPDM may be damaged, contaminated or deteriorated to the point where a larger section needs to be removed and replaced.

That’s why I wouldn’t look at a photograph of an old repair and immediately decide how it should be repaired.

You need to inspect what is actually there.

Does this mean the roof needs replacing?

No, not necessarily.

This is an important distinction.

Poor previous repairs don’t automatically mean an EPDM roof needs to be replaced.

If the main membrane is still in reasonable condition and the problems are isolated, repairing those areas properly can make much more sense than replacing the entire roof.

The question changes when you start finding these repairs everywhere.

If there are dozens of failed patches, deteriorated details, open seams, damaged membrane and repeated historical repairs across the roof, there comes a point where continually spending money on individual repairs may no longer be the best option.

That’s when I would start looking at the roof as a whole.

What are the options?

There are several possibilities, depending on what an inspection finds.

For me, the decision comes down to the overall condition of the roof.

If 90% of the roof is still doing its job, replacing the whole thing because of a handful of bad repairs doesn’t make much sense.

But if you’re constantly chasing leaks and repairing previous repairs across an ageing membrane, you have to start looking at whether that money would be better put towards a longer-term solution.

Can you repair over an existing EPDM patch?

Sometimes an existing repair can form part of a new repair, but I wouldn’t make that decision without first checking its condition.

If the existing patch is loose, cracked or poorly bonded, putting another patch over it doesn’t fix the problem underneath.

The new repair is only as good as what it is attached to.

Where possible, I prefer to get back to sound material, properly prepare the area and build the repair from there.

It may take longer, but you’re actually dealing with the problem rather than hiding it.

What I would do with a roof like this

The first thing I would do is inspect the entire roof rather than concentrating only on the areas somebody has already repaired.

Previous repairs tell you where problems have occurred before. They don’t necessarily tell you where the next problem is going to be.

I’d look at the condition of the main EPDM membrane, seams, parapets, penetrations, drains, skylights and other details. I’d also look at how widespread the previous repairs are.

From there, you can separate the roof into priorities.

Some areas may need immediate attention. Others may simply need monitoring. Some old repairs may still be doing their job and don’t need touching at all.

That gives the building owner or property manager a much better picture than simply applying another tube of sealant every time somebody sees something that doesn’t look right.

An example of an unsuitable repair product deteriorating and separating from the existing EPDM roof.

The bottom line

There is nothing wrong with repairing an EPDM roof.

Done properly, repairs and preventative maintenance can extend the service life of an EPDM roof for years.

The problem is when incompatible products are used, preparation is poor, or new material is continually applied over old failing repairs.

A quick repair can be cheap.

Repairing that repair several years later can be considerably more complicated.

And sometimes the best thing you can do is stop adding more material, clean the area back and find out what you’re actually dealing with.

Frequently Asked Questions

Can you use regular roof sealant on an EPDM roof?

Not every roofing sealant is compatible with EPDM. Products should be selected specifically for the membrane and the type of repair being carried out.

Can old EPDM roof repairs be repaired again?

Yes, in many cases. The existing repair first needs to be inspected to determine whether it is sound enough to remain or whether failed material should be removed before carrying out the new repair.

Does a badly repaired EPDM roof need replacing?

Not necessarily. If the main membrane remains serviceable and the poor repairs are localized, targeted repairs may be a much more economical option.

Why do EPDM roof patches peel off?

There can be several causes, including poor surface preparation, contamination, incompatible products, ageing materials and movement of the membrane. The cause needs to be assessed rather than assuming every failed patch has the same problem.

When should an EPDM roof be replaced instead of repaired?

Replacement becomes worth considering when deterioration and previous repairs are widespread, leaks are recurring, or the cost of continually maintaining the existing roof no longer makes financial sense.