The short answer
Published ranges put zinc at around a century when designed and fitted well, lead at 50 to 100 years and EPDM single-ply at 20 to 30 years or more. Torch-on felt is quoted at 10 to 20 years by one guide and far longer by another. Treat every figure as a typical range rather than a guarantee, and remember that a maker's warranty describes its own cover, not the life of the roof.
What do the published figures say?
No single number settles this, because sources disagree and each looks at different products. The table collects ranges from third-party guides. Treat it as a starting point, not a forecast.
| System | Typical life quoted |
|---|---|
| EPDM single-ply | 20 to 30 years or more (GreenSpec); 30 to 50 years (Less) |
| Torch-on felt | 10 to 20 years (Less); 30 years or more if well maintained (CORC) |
| GRP | 25 to 40 years (Less) |
| Lead sheet | 50 to 100 years (Less) |
| Zinc | over 100 years when designed and installed correctly (VMZINC), occasionally nearer 60 |
The spread is the message. Less notes that workmanship alone can separate a felt roof that reaches 20 years from one that fails inside 10.
Where sources disagree, the safer planning assumption is the lower end of the range. A roof that exceeds it is a bonus, whereas one that falls short is a surprise nobody budgeted for.
Why do two identical roofs age differently?
Water that cannot leave the roof does the damage. Ponding on a low spot, blocked outlets and a failed fall all keep water against the membrane. Design guidance for single-ply roofs aims for 1:40 at design stage, which leaves a finished fall of no less than 1:80, and a roof laid flatter than that struggles from the first winter.
Detailing matters as much as the main sheet. Laps, upstands, penetrations and plant bases are where membranes fail first, long before the open field of the roof. Foot traffic from engineers visiting plant is another quiet cause of wear, and a walkway path protects the sheet. Sun, wind and fumes from extract fans all play a part too.
A roof inspected twice a year, cleared of debris and mended at small defects will outlast the same roof left alone. Our page on repairing a roof while the business keeps trading shows how upkeep fits around a working site.
Design life also assumes the roof is used as intended. Plant installed later, heavy storage on a flat deck or an unplanned rooflight can change loads and drainage, and the covering pays for it.
Is the longest-lasting roof the best-value one?
Not automatically. A zinc or lead roof costs more to lay and suits particular buildings: offices, showrooms, period properties and anywhere the roof is on show. A warehouse with a large flat area and plant on top is often better served by a single-ply or built-up system, which can be renewed in sections as budget allows.
Think about cost per year of service, but also about disruption and risk. A roof that fails early over a building full of stock or servers costs far more than the roof itself. Our commercial roof systems page compares the main build-ups side by side.
Phasing is another benefit. Replacing a quarter of a large roof each year spreads the cost and keeps the rest weathertight, provided the new sections are properly tied into the old ones.
How is lifespan different from a warranty?
Makers' warranties on single-ply are often quoted at 20 to 25 years, which Less calls standard for EPDM. A warranty comes with conditions: approved installation, specified detailing and sometimes registered upkeep. It tells you what the maker stands behind, not the real service life of the roof. Marley makes the same point about tiles, saying its expected-life figure is not a guarantee.
Our workmanship carries a ten-year written guarantee. It speaks for our labour and says nothing about how long a material lasts. Neither a warranty nor a guarantee promises a roof will reach the top of a range. Keep the paperwork for both, because a later buyer or tenant's solicitor will ask to see it.
Ask any contractor which parts of the build-up a guarantee covers: workmanship only, or materials too, and for how long. Hold the answer in writing alongside the specification.
How can you tell where your roof sits in its life?
A survey separates a roof that is simply old from one that has genuinely run out. Photographs of laps, seams, upstands and drainage show whether the membrane is still stuck down and flexible, and whether water is finding a way beneath it. A roof with localised faults can often be repaired, whereas one that has failed across its whole area usually cannot.
That judgement is the difference between a repair that buys several more years and money spent on a sheet at the end of its life. Our commercial roof survey brings photographs of your roof and a written quote. Domestic flat roofs follow different rules, so use the flat roofing pages if the building is a house.
Moisture is the usual hidden problem. Wet insulation beneath a membrane that looks fine on the surface shortens life and raises heating bills, and only a survey with checks at several points finds it.
Layers, drainage and the next re-roof
When a roof does reach the end, what lies beneath decides the next step. Our page on how many layers a commercial roof has explains the deck, vapour control, insulation and membrane, and why overlaying is only sometimes possible. Start from the commercial roofing hub for every system we work on.
Keep records of every repair, because a pattern of faults in one corner points to a drainage or structural cause worth fixing.