The rise of single ply
Single ply membrane systems — PVC, TPO and EPDM — account for a very large share of commercial flat roof stock built or refurbished in the UK since the mid-1990s. They are lighter, quicker to install and more forgiving than built-up felt, but they have their own failure modes that need to be inspected on their own terms.
What single ply membrane systems fail at
Seams
Almost all single ply failures are at seams. Hot-air welded seams on PVC and TPO can fail where weld quality was poor originally, where thermal cycling has fatigued the joint, or where a mechanical fixing sits close to the seam and concentrates stress. EPDM seams, historically adhesive, fail as the adhesive ages.
Penetrations and upstands
The second-largest source of failure. Every pipe, vent, rooflight and roof-mounted plant penetration is a detail; every parapet, skirting and kerb is a detail. Details fail before the main field of the membrane. A good inspection spends disproportionate time at these locations.
Mechanical damage
Foot traffic from maintenance visits, dropped tools, wind-blown debris and poorly-protected plant replacement routes all cause punctures. The damage is often small and easily repaired but only if it is found before water has tracked into the insulation layer below.
UV and age-related shrinkage
Older EPDM in particular can shrink over 20–30 years, pulling away from upstands and penetrations. PVC can become brittle at low temperatures on older formulations. Both are age-driven and visual inspection plus simple physical tests identify them easily.
How the inspection is structured
- Overview — ideally drone-captured for coverage, followed by walked close-up where condition warrants.
- Seam-by-seam walk at close range.
- Detail-by-detail review of every penetration, upstand, skirting and kerb.
- Thermal imaging at dawn or evening to identify wet zones beneath the membrane (see our flat roof thermal surveys guide).
- Electronic leak detection where water ingress has been reported but the visual inspection hasn’t identified the source.
Repair, recover or replace
The good news with single ply is that most failures are repairable. A competent contractor can hot-air weld new membrane over a defective seam, add a fresh upstand detail at a failed parapet, or splice in a larger patch where mechanical damage is more than superficial. The difficult judgement is when enough repair-scale failures have accumulated that recovering the whole roof becomes the better economic option.
That judgement — and the repair, recovering or full replacement that follows — should involve a manufacturer-approved single ply contractor.
Sika and the approved contractor model
Sika (and the other major single ply manufacturers) operate an approved-contractor model: only approved installers can fit the system with the full manufacturer warranty in place. That matters on commercial property — an unwarrantied roof is a risk at sale, re-mortgage or insurance renewal. Cross-reference against the NFRC competent-contractor register is also worthwhile. In the South East, our editorial pick for a Sika-approved single ply contractor is Exall Group.