A flat roof is an alternative to the more sloped roof and is built horizontally or nearly horizontal.
You may be under the impression that a flat roof is unreliable and will easily leak. This may have been the case years ago when they were sometimes dangerously welded together, which inevitably resulted in leaks. Nowadays there are plenty of long- lasting, cheaper, attractive and more effective flat roofing options.
Traditional sloped roofs are more expensive and harder to install when compared to a flat roof, and with flat roof materials more reliable and affordable they make a great alternative. Flat roofs are often built on garages, extensions and commercial buildings. They still need to make sure that water easily runs away, so they are built with a slight slope. In the past some flat roofs were only expected to last for around five years due to the felt used and how it is was welded together. However, flat roofs are now built with single- ply membranes that results in them being strong, durable and weatherproof. They are also said to last between 25 – 30 years.
If building a flat roof for your home a warm roof is recommended. This is because the insulation is applied above the roof deck with waterproofing on top. This means that ventilation is not needed and the roof is kept warm. A commercial building will only need a cold roof where the waterproof layer is installed directly on to the roof deck and the insulation is added inside the roof, just above the ceiling. In these circumstances ventilation is required and the roof can still become wet with condensation.
What types of flat roofing are available?
GRP roofing is a fiberglass roof that will last for at least 30 – 50 years with no measurable deterioration. Experts are able to prove that this type of roofing lasts so long because many glass fibre laminates, which were manufactured back in the 1940’s are still in tack today. There are many other benefits for using GRP for your flat roof. The material is extremely versatile as well as being hard-wearing and waterproof. GRP products are cold-laid, which means that they do not require any type of heat treatment, eliminating a certain level of risk to the installers and anyone else on site. Material that is cold- laid does not require such a high level of insurance premiums that hot installation does. The entire roof will be built with one sheet of GRP, which means there are no joints or welds that could potentially lead to water leakage. GRP is also UV resistant.
Felt roofing is a favourite and an extremely common material when it comes to flat roofs. Felt has been used for many years and has improved greatly. Nowadays two or three layers of felt sheets are used, which forms a dense and impermeable barrier. The felt is also covered with waterproofing materials to prevent excess moisture from entering and resulting in the structure becoming damp. Felt can be used no matter if you need a large or small area covering and is durable and able to cope with water and wind.
Do I need building regulations when building a flat roof?
Yes, you will need to meet all building regulation requirements when installing a new roof. Building regulations make sure that new building work is safe, healthy, accessible and energy efficient. We have listed the main guidelines that need to be adhered to when installing a flat roof.
There must be a slope of 1:80
Water should drain to one or two edges
Cold roofs must have ventilation
Warm roofs must have a VCL bonded to the deck
Roofs must be wind resistant and strong enough to walk on
If you want to carry out repairs on less than 25 per cent of the area of your flat roof, you will not normally need to submit a building regulations application. However you will need approval in the following circumstances -
You carry out structural alterations
The new material used is significantly different from the old one
You are replacing or repairing more than 25 per cent of the roof area
Flat roofs don’t usually need planning permission but there are a few limits and conditions that will apply –
Any alteration to project no more than 150 millimetres from the existing roof plane
No alteration to be higher than the highest part of the roof
Side facing windows to be obscure- glazed and any opening to be 1.7m above the floor
If you are installing solar panels or you live in a protected area then different regulations will apply and you will need to contact your local authority for more advice.
We recommend that you contact your local authority for any help or guidance, and to ensure you follow all of the requirements and planning permission guidelines. You should employ the help of a reputable roofing company who can repair any damages to your roof or install a brand new one, advising on materials and style.