Single Ply Membrane Roofing: Types, Fixing Methods and Pros and Cons

Single ply roofing is a flat roof system made from a factory-produced sheet of synthetic membrane, laid in one layer over the insulation. It is common on commercial buildings, schools and large extensions, and it is increasingly used on bigger domestic flat roofs too. Compared with felt, it offers stronger joints and fewer layers, and compared with GRP, it is lighter and more flexible.

This guide explains how single ply membrane roofing works, the main types, how it is fixed, its pros and cons and what to ask before you choose it. For a comparison with felt, EPDM and GRP, see our guide to flat roof materials.

What Is a Single Ply Membrane?

A single ply membrane is a flexible waterproof sheet, usually 1.2 to 2 mm thick, that is rolled out over the flat roof deck and insulation. Unlike traditional felt, which is built up from two or three layers, a single ply roof uses one layer of membrane with sealed joints. The sheets come in large rolls, so a big roof can be covered in a small number of pieces.

The membrane is often reinforced with a polyester or glass fibre scrim, which gives it extra strength and stops it from stretching or tearing.

Types of Single Ply Membrane

PVC (Polyvinyl Chloride)

The most common single ply membrane in the UK. PVC is flexible, resists UV and weather, and the joints are sealed by hot-air welding, which fuses the sheets into one continuous layer. It is available in a range of colours, and many products include flame retardants.

TPO (Thermoplastic Polyolefin)

A newer membrane that is also welded with hot air. TPO is usually light-coloured and reflects heat, and it does not contain chlorine or the plasticisers used in PVC. It is popular where a reflective, recyclable membrane is wanted.

EPDM (Ethylene Propylene Diene Monomer)

A synthetic rubber, usually supplied in very large sheets and bonded with adhesive or tape. EPDM is technically also a single ply membrane, but it is fitted differently from PVC and TPO and is more often seen on homes. See our guide to EPDM roof edge trim for how EPDM roofs are finished at the edges.

How Single Ply Membranes Are Fixed

• Mechanically fixed: screws and plates are fixed through the membrane at the edges and laps, and the next sheet is welded over them. This is light and fast, and it is good at resisting wind uplift when designed correctly.
• Fully adhered: the whole sheet is bonded to the surface with adhesive. It gives a smooth finish and is good where the roof is walked on, but it needs a clean, dry and compatible substrate.
• Ballasted (loose-laid): the sheet is laid loose and held down by stone or paving slabs. It is easy to install, but the weight needs a strong structure.

The right system depends on the building, the roof size, the wind exposure and the structure. Your installer should explain which method suits your roof and why.

How a Single Ply Roof Is Built Up

On most modern roofs, the membrane sits at the top of a warm roof build-up.

1. Deck: plywood, OSB, concrete or metal.
2. Vapour control layer: stops moist air from rising into the insulation.
3. Insulation: rigid boards, such as PIR, laid above the deck.
4. Separation or cover layer (sometimes): protects the membrane from the insulation.
5. Single ply membrane: fixed and welded to form the waterproof layer.

Our guide to warm roof construction explains the layers, and if you are looking at the older method, our article on cold roof construction shows how it differs.

Advantages of Single Ply Roofing

• Strong joints. Welded seams on PVC and TPO fuse together, which is more reliable than overlapped felt laps.
• Light weight. The membrane adds very little load to the structure.
• Quick on large roofs. Wide sheets cover a lot of area per roll.
• Good UV and weather resistance. Quality membranes hold up well to sun, frost and rain.
• Pre-formed details. Corners, pipe collars and upstands come ready-made, which makes the work neater.
• Reflective options. Light-coloured membranes reduce heat build-up on the roof surface.
• Often recyclable. Many membranes can be recycled at the end of their life.
• Long life. Typical lifespans are quoted at 25 to 35 years for good systems.

Disadvantages of Single Ply Roofing

• Specialist installation. Welding the seams correctly takes training, and many general roofers do not offer it.
• Higher cost than felt. The materials and the specialist labour usually cost more.
• Sensitive to weather during fitting. Welding in rain, frost or strong wind can compromise the seams.
• Damage from sharp objects. Punctures can occur from tools, debris or careless foot traffic.
• Compatibility. Some membranes react badly with certain insulation boards, adhesives or older bitumen surfaces, so the system must be matched.
• Less common on small domestic roofs. EPDM or GRP are often simpler choices on a small extension.

Single Ply vs Other Flat Roof Coverings

Details at Walls, Edges and Penetrations

As with any flat roof, most leaks start at the details. Where the membrane meets a wall or a rooflight, it is turned up as an upstand and sealed under a flashing. Our guide to roof flashing explains how these joints are weatherproofed, and it is worth asking your installer to describe how each detail on your roof will be done.

Maintaining a Single Ply Roof

• Inspect the roof twice a year, and after storms.
• Clear leaves and debris from the surface and outlets.
• Look for lifted seams, punctures and signs of ponding water.
• Keep foot traffic to a minimum, and use walkway pads where access is needed.
• Avoid solvents, oils or sharp tools on the membrane.
• Repair small damage quickly, because patches are easier when the surface is clean and dry.

What to Ask Your Installer

• Which membrane and which fixing method do you recommend, and why?
• Are you trained or approved by the membrane manufacturer?
• What is the full build-up from deck to membrane, and what U-value will it achieve?
• How will you detail the edges, upstands and outlets?
• What guarantee do you offer, and does it cover materials and labour?
• Does the guarantee depend on using an approved installer?

Frequently Asked Questions

What is single ply roofing?

Single ply roofing is a flat roof system using a single layer of factory-made synthetic membrane, usually PVC, TPO or EPDM, over the insulation.

How long does a single ply roof last?

Good systems are typically quoted at 25 to 35 years, depending on the membrane, the installation and how well the roof is looked after.

What is the difference between PVC and TPO roofing?

Both are hot-air welded single ply membranes. PVC is more established and flexible, while TPO is chlorine-free and usually reflective. The right choice depends on the project and the manufacturer’s system.

Is single ply roofing good for houses?

It can be, especially on larger or complex flat roofs. For small domestic roofs, EPDM or GRP are more common and often simpler.

Can I fit a single ply membrane myself?

Not recommended. The seams must be welded properly and the details need experience. Guarantees often require an approved installer.

Is single ply better than felt?

It has stronger joints, a longer typical life and fewer layers, but it usually costs more and needs a specialist. Felt is cheaper and widely understood.

Final Thoughts

Single ply membrane roofing is a durable, flexible system that suits larger flat roofs and complex details. The quality of the installation matters as much as the product, so choose an approved installer, ask for the full specification and check what the guarantee covers before you agree.