The right covering for a commercial building is the one that suits its shape, its structure, its use and the way it will be looked after. A low-pitch warehouse with a steel frame, a stone-walled mill with a lead-lined gutter, and a flat-roofed office extension are three different problems, and the same product will not answer all three. Searching for the best roof for a commercial building tends to return a single answer. In practice there are five families to choose between, and the decision turns on the building rather than the brochure.
Below we compare single-ply membrane, built-up felt, liquid-applied coatings, profiled metal sheet and insulated composite panels. Lifespans come from published sources and are typical ranges, never promises. For the depth on one family, follow the links to our guides on single-ply membranes and metal roof sheets. The wider service sits at commercial roofing.
Five families, and the questions that choose between them
Before comparing products, answer five questions about the building. What is the pitch of the roof, and can it be changed? What does the structure underneath carry, and what will it tolerate? How often will people walk on the roof, for plant or maintenance? What happens inside, in terms of heat, humidity and noise? And how long does the owner expect to hold the building, or the lease, before the roof comes round again?
The pitch question narrows the field fastest. Sheet metal and composite panels are made to shed water down a slope, and they are happiest with a pitch the manufacturer specifies. Membranes, felt and liquid coatings are continuous waterproof skins, which is why they are used on flat and near-flat roofs where a sheet would let water in at the laps. If the roof is truly flat, a continuous skin is the natural family. If it is a shallow pitch over a large span, metal or composite is more likely.
Which family for which building
| Building | Families most often considered |
|---|---|
| Industrial unit with a shallow pitch | Profiled metal sheet, composite panel |
| Flat-roofed office or shop | Single-ply, built-up felt, liquid coating |
| Old mill with slate or stone slopes | Like-for-like natural covering; metal only on secondary roofs |
| Roof with a lot of plant and foot traffic | Built-up felt, reinforced single-ply, liquid coating |
| Cold store or workshop with strict thermal needs | Composite panel, insulated single-ply build-up |
That table is a shortlist, not a verdict. A survey tells us what the deck is made of and what it can take, which can rule a family in or out.
Single-ply membrane: PVC, TPO and EPDM
Single-ply roofing arrives on site as rolls of manufactured sheet, which are laid over insulation and joined into a continuous waterproof layer. The three common types are PVC, TPO and EPDM. PVC and TPO sheets are joined by hot-air welding, so each seam fuses into the sheet itself. EPDM is a rubber, usually laid in large sheets with glued or taped joints. The sheet can be fixed mechanically to the deck, adhered with adhesive, or held down by ballast, and the choice depends on the deck, the wind loading and what the roof carries.
Published lifespans vary. GreenSpec gives 20 to 30 years for EPDM and for PVC. The Building Centre says more than 25 years for EPDM, 20 to 40 years for PVC, and more than 35 for TPO. Less puts EPDM at 30 to 50 years and notes that manufacturer warranties of 20 to 25 years are standard. The spread is wide because the products and workmanship differ, which is why a lifespan quoted from one source is better treated as a range.
Where single-ply earns its place
It suits large flat roofs where welded seams matter, roofs with awkward geometry, and refurbishments where a lightweight covering protects an ageing structure. It is less forgiving of rough handling: sharp edges, dropped tools and repeated foot traffic can mark a membrane, and walkway pads are usually fitted where plant needs servicing. Repairs are possible, though they must use compatible material and technique.
The full explanation of fixing methods and seams is in our guide to single-ply membranes.
Built-up felt and liquid-applied coatings
Built-up felt is the traditional commercial flat roof: at least two plies of reinforced bitumen felt, laid over insulation, with a mineral-surfaced top layer. Layers are stuck down with hot bitumen or by torch, and the multiple layers give a degree of redundancy that a single sheet does not have. Less describes a well-laid felt roof lasting up to 20 years, with a badly laid one giving out inside 10, and CORC puts well-maintained felt at 30 years or more. Those figures disagree, and the difference is largely about the quality of the laying and the care afterwards.
Felt is a familiar trade, simple to repair and copes well with foot traffic. It is heavier than a membrane, and a torch-applied system needs careful fire precautions around combustible materials. Our guide to built-up felt covers the layers and the life in more detail.
Liquid-applied coatings
A coating system is rolled or sprayed over a clean, sound existing surface, and cures into a jointless skin. Liquids are useful where a roof has awkward upstands, pipes and fixings that would be hard to detail in sheet form, and they let an existing surface be refreshed without stripping it. They need a substrate that is sound and dry, and they are only as good as the preparation. A coating over a saturated roof traps the problem under a new skin.
For that reason, a survey decides whether coating or replacement is the right path, and the deck and insulation beneath are checked before any coating is quoted.
Profiled metal sheet
Profiled steel and aluminium sheet is the usual covering for industrial units, farm buildings and large sheds. The sheets are rolled with ribs or corrugations for stiffness, span between purlins, and are fixed through the crown or the trough with screws and sealing washers. Single-skin sheet is lightweight and quick to lay on a large area. Double-skin build-ups add insulation between an inner liner and an outer sheet, which suits buildings that have to hold heat.
Metal sheet sheds water readily on a suitable pitch, covers big spans with few joints and can include rooflights in the same profile. Its weak points are at the edges, the fixings and the laps. Cut edges can corrode where the coating has been breached, and fixings can loosen with thermal movement. Our guide to cut-edge corrosion on metal roofs deals with the commonest fault, and the product choices are in the guide to metal roof sheets.
Noise and condensation
Rain on bare sheet is loud, and uninsulated metal can drip with condensation as moist indoor air condenses on the cold underside. Neither is a reason to rule out metal, but both are reasons to specify insulation, a liner or anti-condensation backing where the use inside calls for it.
Old sheets
If an older unit carries asbestos cement sheets, the approach changes. HSE guidance treats careful removal of such sheeting without breaking it up as non-licensed work, and badly damaged or shattered sheets as notifiable. The system chosen to replace them is a separate decision from how they come off.
Composite and insulated panels
A composite panel is a sandwich, with a metal skin on each face and an insulating core. It is made in a factory, arrives cut to length and goes on in one operation, so the roof is insulated and weathertight as soon as it is laid. That is why panels are used on cold stores, food units, logistics sheds and workshops with strict thermal or hygiene needs.
What the core does
The core carries the insulation, and its type affects thermal performance, fire behaviour and the way the panel handles cut edges. A panel is chosen to meet the thermal figure the building control body asks for, and to meet the insurer's view on fire performance, so both should be checked before an order goes in. A panel can be an expensive way to buy a covering, but it replaces a covering and an insulation layer in one pass.
Limitations
Panels are less forgiving than separate layers for repair. A damaged panel is usually replaced as a unit, and the joints between panels depend on seals that should be inspected as part of routine maintenance. Panels also need a deck or purlin spacing that suits their span. They are a good answer for the right building, not a universal one.
The panel question has its own guide in our commercial section, so here the point is where it sits in the comparison: it suits new or fully stripped buildings with a defined structure, and it is rarely the answer for a delicate older roof.
Mills, historic buildings and the like-for-like rule
Stroud's valleys have many converted and working mills, and their roofs follow different rules from a modern unit. Stroud District Council lists a run of conservation areas for individual mill sites, and listed status protects a building inside and out. For these buildings the best system is usually the one that matches what is there: slate for slate, stone for stone, lead where lead has always been. Under planning law, like-for-like re-roofing that leaves the external appearance unchanged is not usually development. A listed building, or one in an Article 4 area, still needs a check with the planning team first.
Secondary roofs
Many mills have later additions at the back: lean-tos, flat-roofed stores, a loading bay. These secondary roofs are often the right place for a modern membrane or metal sheet, because they are not the roof the lane sees. What matters is the junction where old meets new, which has to be detailed carefully and that any change in weight is checked. A covering that adds 15 per cent or more to the roof weight needs Building Regulations approval.
Gutters and valleys
Where a mill has parallel pitched roofs, the valley between them is often a lead-lined box gutter. A failed box gutter is a common source of leaks inside, and it is a separate job from the covering above it. We look at it as part of every mill survey.
Choosing, and what to ask for in writing
With the families laid out, the decision comes down to a few tests. Does the system suit the pitch and what holds the roof up? Can it be detailed properly around the plant, rooflights and edges on this roof? Is the lifespan realistic for the owner's plans? Is there a clear route to repair in ten or fifteen years? And does the quote say what goes underneath as well as what goes on top?
Prices matter too, and they are explained in our guide to commercial roof costs. A flat roof replacement is typically priced per square metre, with MyBuilder's 2026 flat roof guide giving £70 to £100 for felt, £90 to £130 for EPDM, £95 to £140 for PVC single-ply and £95 to £150 for GRP. Those are national figures, and exclude your building's own access and structure.
What the quote should show
Ask for the covering, the insulation, the fixings or bonding, the details at edges and penetrations, and the drainage fall to be named in the quote. Ask who guarantees the workmanship, in writing, and what the manufacturer's own warranty covers and for how long. A manufacturer warranty is not a lifespan, and neither is a promise.
We survey first, photograph your own roof, and write a written quote after the visit. Our workmanship carries a 10-year guarantee in writing. Send us the building address, its use and any photographs, and tell us what you want the roof to do over the next decade.