What Is Single-Ply Roofing
Single-ply roofing means a flat roof waterproofed with a single thickness of synthetic membrane — PVC, TPO or KEE polymer — rather than the multiple layers of bitumen felt used in traditional built-up systems. The membrane is supplied in large factory-controlled rolls (1.5m to 2m wide, 15-20m long) and welded together on site with hot-air welders to form a continuous waterproof skin over the whole roof.
It's now the dominant flat roofing system in UK commercial construction because it's faster to install than built-up felt, lighter than asphalt, more reliable than older single-membrane systems like the early 1980s thermoplastic films, and the better systems carry 20-25 year manufacturer warranties when installed by an accredited contractor.
Mechanically Fixed Vs. Fully Adhered
There are two main fixing methods for single-ply on commercial roofs. Mechanically fixed systems (the most common) use thermoplastic-coated washers screwed through the membrane into the structural deck below, with the seam between sheets welded over the line of fixings to keep the heads weatherproof. This is fast to install, suits most metal and concrete decks, and gives the best wind uplift performance on tall or exposed buildings.
Fully adhered systems bond the membrane to the deck or insulation board with a contact adhesive across the entire underside. Used where mechanical fixings are impractical (lightweight or fragile decks, very thin insulation), or where appearance matters (no fixing pattern visible from inside) and on buildings where vibration or thermal movement might loosen mechanical fixings over time.
Detailing Is Everything
On a single-ply roof, the membrane in the field is rarely the part that fails. Failures almost always start at the details — upstands, parapets, drainage outlets, roof penetrations, expansion joints. Manufacturer warranties depend on these being installed exactly to specification: proper kerbs at parapets, factory-formed corners at internal angles, set-in outlets bonded to the membrane, lap-tested welded seams.
We work to Sika Sarnafil and IKO Armourplan technical guidance on every project, lap-test every welded seam with a probe before sign-off, and provide a full handover pack including as-built drawings, material data sheets, lap-test records and the manufacturer's system warranty certificate.
Maintenance & Service Life
A properly installed single-ply roof needs minimal maintenance — an annual inspection to clear debris from outlets, check the perimeter details, and confirm there's no impact damage from foot traffic. The membrane itself is UV-stable, chemically inert and dimensionally stable through normal temperature swings. Service life on a quality system from a major manufacturer is 25+ years, with many achieving 30-40 years before re-covering becomes economic.
When the roof eventually does reach end of life, single-ply over single-ply re-covering is often possible without stripping the existing system, which is one of the major lifecycle cost advantages over traditional bituminous systems.
Frequently Asked Questions
Is single-ply better than felt for commercial roofs?
On most commercial applications, yes — longer warranty, faster installation, lighter weight, better wind uplift performance. SBS torch-on felt remains a sensible choice on smaller projects or where matching an existing felt system.
How long does single-ply take to install?
A 500m² flat roof in single-ply typically takes 2-3 weeks including insulation upgrade. Larger commercial roofs can be installed at 200-400m² per day in good conditions once the deck is ready.
Can you work in winter?
Yes — single-ply membranes can be installed in temperatures down to about 5°C and in light dry weather. Mechanical fixing means no flame, no torches and no fumes, which makes occupied building work straightforward.
Do you handle warranty claims?
Yes. Where we've installed the system as an accredited contractor, we administer any warranty claim directly with the manufacturer on your behalf.
What's the cost compared to traditional built-up felt?
Single-ply is typically 10-30% more expensive per m² than equivalent built-up felt. Over a 25-year horizon the lifecycle cost is usually lower because of the longer service life and lower maintenance burden.