Single Ply vs Bitumen Membrane: Which is Right for You?

Single-ply and bitumen membrane roofing systems are two common choices for commercial flat roofing, each with its own benefits and challenges. In this guide, we look at single-ply vs bitumen membrane to help you determine which option is the right fit for your building.

As experienced roofing experts, our team at Central Group works with both membrane types, recommending the best solution to suit the needs of individual clients. If you need a professional team for an upcoming roofing project, contact us directly on 01432 354 000.

What is Single-Ply?

Single-ply is a simple, high-performance roofing system that consists of a flexible sheet of polymer, typically a synthetic rubber or a thermoplastic. Single-ply can be laid quickly because it consists of only one layer of roofing.

Single-ply is usually made of Ethylene Propylene Diene Monomer (EPDM), Thermoplastic Polyolefin (TPO) or Polyvinyl Chloride (PVC), though other options may be available to suit specific products. Single ply is a common choice for flat roofing projects, where sheets can be laid quickly and easily.

To adhere single-ply to a roofing structure, the membrane must be ballasted, chemically attached or fixed in place mechanically.

What are Modified Bitumen Membranes?

Modified bitumen roofing is a highly durable solution, offering strong resistance to both heat and stress from the weather. This roofing system is made up of a hybrid material that combines asphalt with a plastic polymer or synthetic rubber for improved flexibility and performance.

Unlike single-ply roofing systems, modified bitumen membranes are multi-layer and typically include a mat of either fibreglass, polyester or a combination of both to form the final membrane. Two layers of bituminous membrane are applied to the roof to give optimal protection.

To adhere modified bitumen, roofing specialists can either use the torch-down method, where the roofing material is heated to melt the asphalt and bond the layers, or cold adhesive, where water or solvent-based compounds are used to glue the sheets together.

Benefits of Single-Ply

Cost-Effective Solution

Single-ply is a cost-effective option for roofing as it only involves the application of a single-layer membrane. This means that the cost of the materials is substantially lower, particularly in self-adhered types of single-ply. As single-ply is easy to install and takes less time, the cost of labour is also reduced.

Enhanced Energy Efficiency

Single-ply roofing membranes are designed to have effective thermal emittance and solar reflection, which keeps the interior of buildings cool, reducing overall energy consumption. If installed correctly, single-ply roofing can be airtight, preventing air from leaking out and further improving energy efficiency.

High Flexibility

In addition to being easy to install, single-ply roofing is also highly flexible to different roof types and industry requirements. For example, a single-ply membrane can be used for flat roofs, curved roofs and steep roofs. Thermoplastic-based membranes can be thermoformed to suit a range of roofing styles.

Quick and Simple Installation

Alongside being cost-effective by reducing labour, single-ply being quick and easy to install on site is also beneficial to the timescale of roofing construction. For example, on projects that have a fast turnaround or a strict completion date, single-ply is one of the fastest options for reliable roofing.

Lightweight Design

As a single-layer membrane, single-ply is more lightweight than other roofing systems while maintaining a high level of durability. A lower weight reduces structural load on the property, making single-ply a practical option for refurbishments where heavier roofing may be less suitable. Light sheets can also make it easier to transport roofing systems on-site.

Challenges of Single Ply

Durability

The lightweight nature of single-ply can be just as much a challenge as it is a benefit. As the membrane is so thin, it can be easily punctured, which can cause issues when access to roofing areas is frequently required for maintenance. No additional levels of adhesion can also make this membrane susceptible to wind uplift along the seams. Once a failure has happened, there is no redundancy to prevent water ingress.

Variable Lifespan

The lifespan of single-ply roofing can vary depending on specification and installation quality. It’s worth noting that, as single-ply is directly installed onto the substrate below, there is no protection following failure. Degradation of adhesives due to both UV rays and thermal heating can also potentially lead to the roofing breaking down faster.

Limited Waterproofing

One layer of membrane across the whole roof does not allow for independent waterproofing of different areas and fixtures. As the roofing is not compartmentalised, this means any failure is a whole-roof failure, requiring more of a complete replacement at a higher cost than individual area repairs.

Benefits of Bitumen Membrane

Built to Last

Roofing with a bitumen membrane has a long lifespan, with a high degree of durability due to the fusing of different layers, making both wind uplift and seam issues unlikely. Bitumen roofing has excellent tensile strength and flexibility, which allows for movement within the structure and reduces issues with thermal heating.

Exceptional Weather Protection

Modified bitumen roofing systems provide thorough waterproofing through the application of multiple layers of the membrane. This doubles up protection against water ingress, as if one layer fails, the other will still prevent water from entering the building. Safety breaks can be created in relevant areas, preventing the whole roof from failing.

Long Service Life

The service life of a bitumen roofing system can span decades with proper care, maintenance and prompt repairs as and when needed. Certain types of bitumen roofing can last 20 years or longer. This increased lifespan can make bitumen a cost-effective solution in the long term by reducing the frequency of roof replacement.

Simple Repairs

Bitumen is simple to maintain and repair. New layers may be able to be placed on top of one another and bonded into the existing roofing depending on its condition, allowing for either patch repairs or for the full roof to be overlaid. Bitumen membranes are also easier to access as they are durable enough for foot traffic, requiring no specialist equipment to conduct repairs.

Strong Weather Protection

Bitumen membrane is well-suited to handle the significant weather changes in the UK, from high levels of UV sunlight in summer to ice and snow in the winter. The pliable nature of many types of bitumen roofing allows it to remain flexible in all weathers, preventing shrinking in cold weather and providing effective UV protection in warmer months.

Challenges of Bitumen Membrane

Increased Costs

Bitumen is more expensive than single-ply roofing, both for the initial cost of the material itself and in terms of labour costs. Specialised knowledge may be required for installation in comparison to single-ply, which can also increase the up-front costs of installing a new roof.

Extended Installation Time

Bitumen membrane is installed over several layers and then fused through the use of either cold adhesive or torching. These processes require significantly more time than installing a single-ply roof, as there are more stages to complete. Bitumen installation also has a strong smell, potentially requiring additional planning for live environments where torch-applied systems are used in certain circumstances..

Seam Vulnerabilities

Roof seams in flat roofing systems are the connective space between two rolls of roofing material and require professional sealing with the proper techniques to prevent leaks. Working with a trusted and reputable roofing company like Central Group assures seamless installation of bitumen roofing membrane on all sites.

We ensure all overlaps have a high level of integrity and are reinforced where required to guarantee a continuous waterproof barrier. We also conduct a thorough inspection of all seams before the project is handed back to you.

What to Consider When Deciding Between Single-Ply and Bitumen Membrane

Choosing between single-ply and bitumen membrane roofing can be a difficult task. Some of the factors you may want to consider include:

– Installation: Single-ply is fast to install, while bitumen takes longer and may require clearing the building due to the smell.
– Maintenance: Bitumen roofing can be walked on, making regular maintenance an easier task, while single-ply is less costly but more difficult to maintain.
– Programme Requirements: How fast you need your roofing installed and whether you require phased works should be a consideration in the type of roofing you choose.
– Cost: Bitumen has a higher up-front cost, but a longer lifespan, while single-ply has a smaller installation cost but will not last as long.

Our experts at Central Group can support you in choosing the right roofing system for your site. We have 700+ vetted contractors and over 40 years of experience in delivering quality roofing solutions for your clients across a wide range of industries.

We can conduct a site survey and provide a recommendation for the best roofing option, considering your time frame, budget and any ongoing maintenance requirements. Contact us today to start the process.

Choose Central Group for Roofing & Cladding

Both bitumen membrane and single-ply roofing systems have a range of benefits and challenges to consider, from cost to longevity. At Central Group, we have extensive experience in the professional installation of both roofing systems for flat roofing and pitched roofing. We also offer viable alternatives to consider, such as metal roofing.

Central Group delivers high-quality solutions for roofing across the UK, with over 40 years of experience in delivering roofing systems that suit the needs of our clients. Call us on 01432 354 000 or enquire online today to get a quote and discuss the options available to you for roofing.