Flat roof design ideas, inspiration & pictures

Flat roofs

Far from being outdated, flat roofs are enjoying a resurgence in popularity. Here’s all you need to know about why flat is fabulous.

Why is a flat roof a good option?

If you’re a first-time home-buyer or cost conscious, a flat roof is the most inexpensive way to go. This does not mean that your home won’t be aesthetically pleasing from the inside or outside. As with all design choices, it comes down to what you make of this roof-top style, whether renovating, buying or building your dream home.

The appeal of the flat roof goes far beyond saving roofing costs. Thanks to your perfectly horizontal interior ceiling, how you utilise and design your internal space is limited by your imagination only. Gone are the restrictions of having to adhere to the architectural challenges that come with a pitched roof, slants and angles: you can map out your internal walls – and indeed your internal vertical areas – with precision.

Perfectly straight ceilings also generally mean more comfy, even internal temperatures, especially when various insulation options are taken into account. Ever feel that chill in a house with a pitched roof thanks to an attic-like space created to meet the upward slant of a ceiling? That’s one problem you’re unlikely to have.

It is not necessarily true that a flat roof equals less interior space. The impression of roominess when you look at a pitched-roof structure from the outside is just that: an impression. You still have the option of raising your ceiling fairly high, or creating interior design illusions of space with mirrors and other features that draw the gaze upwards, such as a chandelier or other striking lighting option.

It goes without saying that with a little bit of love and effort, your horizontal roof makes for incredibly inventive outdoor roof-top living or home features. Some creative advantages are:

· solar panels, air conditioning units and satellite dishes are easier to install

· a living garden could be an attractive roof-top reality with a little love

· an envy inducing roof-top patio is much more of a reality on a horizontal surface.

A flat roof lasts an average of 20 years, provided it is installed properly by a professional roofer, although there are some exceptional options that come with a lifetime guarantee.

Types of flat roofs

Built-up roof (BUR)

Typically, a built-up roof is made up of layers of durable, leak-proof materials such as tar and gravel. BUR is the most tried and tested method, thanks to its relative strength, durability and aesthetically pleasing finish. It can accommodate roof-top living better than most other options and is a good insulator of heat. A BUR does tend to be more weighty than other options, so make sure it is supported well.

PVC roof

This is involved when you go the ‘single ply membrane’ route. A variety of roofing materials can be used, but PVC remains the most common choice, of which Sarnafil remains the most superior brand. Make sure to have it professionally installed and use the flat roof materials suggested by your installer.

You could also use a rubberised membrane instead.

Modified bitumen

This involves putting down just a single layer and most homeowners can do this themselves. It is generally a peel back-and-stick down job, with the roofing material comprising some sort of mineral-based adhesive that is resistant to wear and tear. Do not confuse this with the older felt-tip roofs. This modern take on felt uses superior, reinforced materials and modernised methods of application, such as via a big blow torch, are used.

Different types of flat roof material

For each of the various types of horizontal outer ceiling housing covers discussed above, a variety of materials can be used.

While PVC is a popular single ply membrane material option, another one is TPO (Thermoplastic Polyolefin), especially if you object to the use of PVC on environmental grounds. PIB (Polyisobutylene) is another option here.

When it comes to rubberised roofing options – a highly popular alternative to the PVC roof – EPDM is the leading material used. Not surprising, as it is manufactured by leading tyre-maker Firestone. It is mechanically glued to the sub-surface layer and has a lifespan of 30 years if installed properly.

Spray-on coatings are one of the more recently developed roofing materials. The material is sprayed on with a pump, and should be done so meticulously. You can apply it directly to the material below without first using a primer, to form a bonded, waterproof membrane. The ease of installation and reflective surface of the spray has seen this roof solution increase in popularity.

The average cost of installing a flat roof

The following approximate prices are applicable per square metre. Expect to pay more if your roof is higher up than most, your home is in a major city or in a remote area, and if you want to use more expensive materials or need to replace other substrate layers as well. Added insulation, ventilation requirements and improved internal drainage could also see you pay more.

Naturally, the bigger the surface area, or the more complex the job or required installation method, the more you’ll pay.

Compare quotes as well as the guarantees offered.

Modified bitumen or felt roof: £50 to £60, assuming the boards below are in good shape. It costs about £40 for every new board you need to replace.

EDPM rubberised roof, e.g. Firestone: €85, assuming no damaged boards below. The price includes a quality permaroof finish, and new overboarding to bond with the rubber.

Fibreglass and PVC: £90, if there are no boards underneath requiring replacing. The price includes the necessary new overboarding as well as professional trims.

The installation process

The basic design involves a substrate layer of timber or board, held up by joists. The internal ceiling is fixed to the underside of the joists.

Next, you should add a layer of waterproofing and insulation, as required by building regulations. A cap sheet or top layer of protection may be required, especially against fire hazards. You may or may not need to lay down this cap sheet, depending on the materials used for your flat roof.

Remember that a flat roof is even, but not literally ‘flat’ – it should slope at a slight angle or angles to allow for water drainage.

Now place your chosen flat roof material or membrane (see Types of flat roof).

Finally, trim uneven pieces or any joists or timber sticking out to give you a neat appearance. It’s best to use machine trimmers.

Finding a trusted roofing company

A good place to start is the National Federation of Roofing Contractors (NFRC). Alternatively, look for a Competent Roofer as certified by the government’s Competent Person Scheme. They should be in possession of a Building Compliance Certificate, valid for 10 years. Membrane manufacturers will also have a list of approved contractors that can professionally use their materials and build your roof.

The best recommendations though remain via word of mouth, so ask around. Then see if you can get reviews for any of these contractors and be sure to check the comments. It is always a good idea to search for reviews on any contractor. Search the Yellow Pages for competent tradespeople or use one of our trusted contractors.