Whether you are working on a new build project or you are looking to replace an existing flat roof covering, it makes sense to review the options available and identify which is the best flat roof material for you.
Certain methods, such as built up flat roofs (BUR), have been around for more than 100 years. However, in the past few decades, roofing technology has come on leaps and bounds as consumers and installers alike have demanded more energy efficient and inexpensive flat roofing systems.
To identify the best flat roof covering for you, firstly, consider the following:
- Budget: how much are you looking to spend and will this be enough to invest in an option with a longer lifespan?
- Climate: will the roof be subject to heavy rain, freezing temperatures or intense sunlight?
- Timeline: how quickly are you looking for the roof to be installed?
- Installer: will you be installing it yourself or will this be undertaken by a roofing contractor?
Flat roofing material options
Built Up Flat Roof (BUR)
Built up flat roofs (BUR) are constructed by applying several layers of molten tar and gravel to the roof and creating a watertight seal. It is one of the most common materials for flat roofs and has been used for over 100 years.
- Offers good insulation
- Low maintenance
- Offers a minimum lifespan of 10 years but can last up to 20 years
- Installation can be time-consuming due to the number of layers which need to be created
- Installation can be messy and can give off unpleasant smells
- Very heavy construction which could mean the roof has to be further reinforced to hold the weight
- Can be expensive to install
- It is not advised to live in the property during installation
Modified Bitumen Flat Roof
Modified bitumen is a single-ply roofing material available in sheets, which are made from bitumen, a product formed by the distillation of crude oil which has been mixed with sand or crushed limestone.
To install a modified bitumen flat roof, the sheets are heated with a blow torch or heat gun and installed using a roller, with the heat allowing the material to adhere to the roof surface.
It can also be used as an underlay beneath slate or tile roofs, whilst an extra coating of sand or gravel can be added to the top to improve its look.
- Relatively cheap option
- Quick and easy to apply
- Easy to repair
- High reflectivity ratings, allowing the surface of the roof to stay cooler in the sun
- Not suitable for heavy foot traffic
- Prone to tearing
- As heat needs to be aimed directly at the roof surface, installation can be dangerous if not done properly
- Bitumen can be a hazardous substance
Ethylene Propylene Diene Monomer (EPDM) Rubber Roofing
EPDM (ethylene propylene diene monomer) rubber is a synthetic material made up of recycled rubber, making it an environmentally friendly choice.
It is installed by seaming together strips with adhesive, which means that any noxious/poisonous chemicals that are released when heat applying other materials like bitumen are avoided.
- Proven lifespans of over 50 years
- Environmentally friendly choice – ranked at the top of the rankings for low impact membranes by international environmental agency, Greenpeace
- Offers excellent insulation
- Repels moisture
- Highly resistant to UV and infrared light
- No blistering, cracking or rotting
- Flexible, expands and contracts with weather
- Can easily be repaired
- Dry conditions are needed for installation
- Installation may need to be undertaken by a professional on roofs featuring skylights, chimneys and vents
- Leaks can occur if not installed properly
PVC is a material made by combining ethylene and chlorine to produce ethylene dichloride (EDC) which is then processed to produce vinyl chloride monomer (VCM), polymerised into vinyl resin and compounded for durability and flexibility.
PVC roofing is installed with a heat gun to ensure seam strength and make the material resistant to leaks and the wind. It is then adhered to the roof either by using an adhesive, by using heavy duty screws or by using a ballasted roofing system.
- Strong and durable – heat welded seams will last a long time but heat application runs its risks
- Lifespan of around 20 years
- Resistant to pollutants
- Resistant to wind
- Releases toxins into the environment during manufacture and disposal
- The additives that aid in flexibility can break down and pose problems after 20 or so years
- Installation can be tricky
Glass Reinforced Plastic (GRP) is made up of polyester resin and chopped strand mat glass fibres, mixed together to form a laminate.
- Good at resisting moisture so well suited to more humid/wet conditions
- Offers good insulation
- No joints or seams
- Can be noisy in the rain, something to consider if extending your living space
- One of the most expensive options for a flat roof
- Inflexible, if moisture gets trapped under the membrane this can cause blistering
- Can only be installed in dry, mild conditions
- Will not cure if installed in cold weather
- It is not considered the best option for larger roofs