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A Beginner's Guide to Flat Roofing Systems


18th April 2018

When you're looking to install a flat roof on your property or wish to replace your current system, it’s important to gather as much information as possible.

For those who aren't sure about the types of materials available, the advantages of each kind or which one may be suited to your project we’ve put together a guide to flat roofing which should give you the ideal starting point.

An Introduction to Flat Roofing

The term ‘flat roofing’ describes a roof surface that is as almost completely level. Although the name indicates a horizontal surface, a slight angle must be included to allow for the drainage of rainwater. The preferred design of a flat roof fall is 1:40, although this can vary and be anywhere down to 1:80. This depends on the site upon which the structure has been built.

Garage & Porch Flat Roofing - Roof Stores
Garage & Porch Flat Roofing

Flat roofs were uncommon in the UK until after the Second World War. As a mass rebuild of housing got underway, it was discovered to be a cheaper alternative to the traditional pitched roof style. Warmer climates, especially in Mediterranean countries, have long since adopted flat roofs as they ensure that the temperature inside remains stable and less likely to suffer from intense heat spikes.

In most cases, flat roofs are found on outdoor living or storage spaces, house extensions and industrial buildings. There are still some residential properties that require flat roofs due to planning regulations. It is also a style gaining favour with architects for houses with a more modern, minimal design aesthetic.

Types of Flat Roofing

There is a wide range of flat roof materials available and which one you require mostly comes down to personal preference. There isn’t an industry consensus on which one produces the best results. The buyer’s main concerns should be the price and guarantee provided by the manufacturer. It's recommended to make sure that the material you choose has at least a 20-year guarantee to ensure longevity.

Once you have decided that a flat roof should be installed, there are several considerations to bear in mind. This will include things such as material performance, the complexity of the structure and the aesthetic appeal.

As with any roof installation, the key is to find the right company who can give you the assurances you need that the job will be completed to the required standard. They will also be able to advise on the best type of roof covering. This is based on the usage, local environment and the budget available to you.

Torch-on Felt

Two or three layers of bitumen sheet are applied by gas torch to form the roof coating. This is a very cost-effective option. However, there are different grades available that provide better quality along at a higher price point.

Torch-on Bitumen Felt - Roof Stores
Torch-on Bitumen Felt

One of its advantages is its malleability and a multi-layering approach that stands up well to foot traffic. A naked flame is used to heat the felt during installation, so necessary precautions must be made to prevent the fire risk – products like the Anderson Toptorch SBS SB2 Torch On Underlay provide a safe solution that doesn’t break the bank.

PVC Single-ply Membrane

This is one of many single-ply membrane options, with other variants available including PIB, TPE and TPO. Gas is polymerised to form a vinyl resin which creates a durable composite. This material can be made in numerous different colours.

They generally provide good value for money, although it requires a more specialised fitting process from approved installation companies. This option is ideal for any number of industrial, commercial and domestic roofs.

EPDM Rubberised Roofing

A common choice for installers, EPDM can be reusable if it has been fixed into place mechanically or loosely laid. The durability of the material is one of its main advantages. It also offers high levels of waterproof protection against UV light.

EPDM Rubber Roofing - Roof Stores
EPDM Rubber Roofing

Another reason it is widely used is that it's easy to install and can be quickly cut to size for tailored dimensions. FIX-R EPDM Membrane has a reputation of lasting for up to, and over, 50 years.

GRP Fibreglass Roofing

A paint-on solution such as liquid roofing allows for more flexibility during installation. It also works well on roofs that are not of a standard size or shape. While it may be lightweight, GRP systems remain strong and durable. This offers protection against heavy foot traffic and any natural movement that occurs within the building. Learn more about GRP by researching CrysticROOF GRP Resin, which is used in conjunction with CrysticROOF GRP Topcoat to provide a robust fibreglass roofing solution.

What are the Advantages of Flat Roofing?

Flat roofs offer three distinct benefits. Their aesthetic, price-point and low maintenance requirements make them a popular choice for certain structures.

  • Design: Flat roofs are typically used for smaller structures such as extensions and garages, although it's not uncommon for them to be used for larger structures such as airports or supermarkets. The waterproof membrane protects the structure and, while some rainwater may be retained, this will drain off into a hopper. A flat roof also creates more space inside the structure compared to pitched roofing. This makes the most out of the dimensions of any sized building.
  • Cost: Fewer materials are generally used in the construction of a flat roof making it a considerably cheaper option compared to a pitched alternative. The installation time is also significantly shorter and can often be completed in only one day for smaller buildings.
  • Low Maintenance: A flat roof tends to be a lot easier to inspect and repair than a pitched roof. This also means that checks can be arranged more frequently. Cleaning the gutters and checking the sidings is a far easier process which means your roof should stay in great condition for an even longer period.

When are Flat Roofs Used?

Flat roofs are often used on structures that are not a standard part of the living area. For example, extensions and garages feature flat roofs, as do outdoor living spaces that have been built in the garden.

One of the main reasons is that flat roofs, which generally feature a pitch of 10° and under, are not as thermally efficient as pitched roofs. This makes them ideal for dry, warmer environments where heat retention is a lot lower.

Flat Roofing 3D Design Plan - Roof Stores
Flat Roofing 3D Design Plan

Planning restrictions in some towns will require flat roofing to be installed. For example, if the use of a pitched roof is deemed to be too high as it may obscure the view of surrounding residents and possibly block out light, a flat roof is likely to be the recommended alternative.

A flat roof is usually the preferred choice for extensions likely to be positioned nearby to an existing structure. There are also instances where a new flat roof is installed to replace an outdated roof system. This is often the case with corrugated tin roofs which are no longer allowed under current UK building regulations.


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