"Rubber roof" covers a few different products, and the differences matter less than one detail almost nobody asks about: how it's stuck down.
What EPDM is
A synthetic rubber membrane, laid as sheets over a flat or very low-pitched roof. It's flexible, it copes with a building moving and with temperature swings, and it goes on without a naked flame — which makes it useful where hot works aren't allowed.
Its reputation is good and mostly deserved. The failures that give flat roofing its bad name are usually about installation rather than the material.
The bit that actually matters: the backing
Most EPDM is bonded to the deck with adhesive, and that's where the quality of the installation shows up.
When a rubber roof fails, it's usually the bond that let go rather than the membrane — and usually because it wasn't fitted to the manufacturer's instructions. The most common version of that is the deck: it has to be dry when the adhesive goes on. Rush that, or take a chance on the weather, and you've built the failure in on day one. The rubber itself will outlive the mistake.
We fit the Resitrix version of EPDM, which has a bitumen-based backing. It's a self-adhesive product, and the joints are hot air welded rather than glued or torched. That's a genuinely different way of putting a roof together from the standard adhesive build-up.
The practical reason we like it is what that means for where it can go: no naked flame on site. On an occupied building, a school, or anywhere a hot works permit would be refused, that's often the thing that decides the system.
Where EPDM is and isn't the answer
It isn't automatically right. These are the four systems we work with day to day and roughly where each earns its place:
- Built-up bitumen (felt) — the traditional layered system, typically three layers. Proven, cost-effective, and what we most often recommend. It's also where we can offer our longest guarantee terms, which is the honest reason it stays our default rather than nostalgia.
- EPDM and Resitrix — durable rubber membranes, good with weather and movement. Resitrix is self-adhesive with hot air welded joints, which makes it an excellent choice where hot works aren't permitted.
- Single-ply membranes — lightweight sheets welded at the seams, well suited to larger commercial and industrial roofs.
- Liquid coatings — brushed or rolled to a seamless, fully bonded finish. Useful on awkward shapes and roofs with a lot of penetrations, and they go on cold, which makes them the answer where hot works are restricted — occupied buildings, schools, anywhere a naked flame won't get signed off.
If someone recommends one system for every roof, that's worth a question.
The things that decide whether any flat roof lasts
Product choice is maybe third on the list.
The deck underneath
This decides more than the product does, including whether you need a new roof at all. A sound timber deck makes an overlay possible — cheaper, less waste — but it doesn't make it automatic. Often the covering has failed badly enough that replacing it is the better call regardless, and sometimes that's the customer's decision rather than ours. A water-damaged or failing deck settles it: the whole covering comes off.
Where the roof can be reached, or its underside seen from inside, we assess it on the first visit and tell you there and then. Where it genuinely can't be seen — too high to get onto safely, or a plasterboarded ceiling in the way — the written quote carries a priced contingency for deck replacement. You know that number before you agree to anything.
The fall
"Flat" is a misnomer. Every roof we lay has a fall built in: a gradient you won't see by eye, taking water gently to the outlet. Depending on the roof it might be a few millimetres or as much as 150 mm.
Water can still sit on a correct fall after heavy rain, and that isn't a fault — the material is designed to be sat under. A roof with no fall is a different matter.
The joins and the penetrations
Flat roofs almost never fail in the open middle. They fail at the joins, where one sheet laps over the next, and at penetrations — skylights, vents, outlets, anything cut through the covering.
That's where the time goes on a good installation, and it's where to look on a bad one. On a bitumen roof there's a specific tell: as each strip is bonded down, bitumen from underneath melts and squeezes out along the edge to form a bead. A continuous bead along a seam means a sealed unit. No bead, no seal — however tidy it looks from the ground.
Insulation, if it needs any
Some flat roofs over unheated space — a garage, usually — don't need insulation at all. Where it's needed, a warm deck puts it above the deck and is the better choice over a heated room. A cold deck insulates between the joists and is shallower, which matters where height is tight — but ventilation is the whole game: the void above the insulation has to breathe, or moisture condenses against the underside of the deck. That's the single most common reason a cold deck fails.
What we'd actually do
Come and look, free. Tell you what the deck is doing and which system suits the building — sometimes more than one would work, and they carry different guarantee terms. Then a written quote within seven days with the workmanship guarantee written in.
Ask us to look at your flat roof, or read what decides the price of a new roof first.