A flat roof is a roof which is completely flat or has a low pitch up to approximately 10°. Beyond this the roof would be referred to as a pitched roof. Often flat roofs are referred to as ‘low-sloped’ roofs. According to the NRCA (National Roofing Contractors Association) a ‘low-sloped’ roof has a fall of less than 1:4, so for every 4m along the roof falls 1m.
What is the purpose of a flat roof?
Flat roofs serve many purposes, some of which are more obvious than others.
Additional space
Flat roofs can provide extra usable outdoor space that can be used for many things, such as gardens, barbeque areas, or relaxation areas.
Energy efficiency
Flat roofs can help keep utility costs down, especially in warmer climates, because they don’t trap warm air or allow cooled air to escape like sloped roofs do.
Commercial use
Flat roofs are often used for commercial buildings with large span roofs, such as those that house HVAC technologies and plants. They are also a popular location for solar panels.
Residential use
Flat roofs can be a valuable addition to residential apartment buildings, extending living and communal areas with gardens and roof terraces.
Car parks
In some cases, flat roofs can also act as car parks.
Cost
Flat roofs can be cheaper to construct initially and can also save money if extensive repairs are needed.
Common flat roof waterproofing systems
There are many different solution for waterproofing a flat roof. Some flat roofs are better suited to certain types of waterproofing than others. It is important to analyse all the properties of the flat roof and the waterproofing system when deciding what waterproofing system to specify.
Asphalt
Asphalt is a composite material made by combining bitumen and aggregates, such as crushed stone, sand and gravel. There are several different grades of asphalt for application on varying degrees of pitch.
EPDM (Ethylene Propylene Diene Monomer)
EPDM is a single ply membrane made from synthetic rubber. It can be applied by ballasting, mechanically fixing or fully adhering. The laps are hot air welded.
Modified Bitumen
Bitumen membranes are most commonly modified with APP (Atactic Polypropylene) and SBS (Styrene-Butadiene-Styrene). These modifications add characteristics to the membrane such as flexibility and different melting points. Bitumen membranes can be applied by gas torch, mechanically fixed or adhered.
Cold Applied Liquid
Liquid roofing, as it’s often referred, has a fully flame free application. There are several different systems including Flexible Polymer, PU (Polyurethane) and PMMA (Polymethyl Methacrylate).
PVC (Polyvinyl Chloride)
PVC or vinyl roofing is made from petroleum or natural gas combined with salt, modified with plasticizers and UV stabilisers. This single ply membrane can be ballasted, mechanically fixed or fully adhered with the laps being hot air welded.
TPO (Thermoplastic Polyolefin)
TPO single ply membranes are created by thermally fusing 2 layers of TPO polymer on either side of a reinforcement layer. It does not contain plasticizers and can be installed by ballasting, mechanically fixing or adhering with the laps being hot air welded.
GRP (Glass-Reinforced Plastic)
GRP is a liquid applied membrane with a glass-fibre reinforcement layer providing a lightweight waterproofing material for many diverse applications including boats, ponds and of course roofs.
Conclusion
Now that you know what a flat roof is and have had a little bit of information about them why don’t you take a look at some of our products or projects. If you’re after a bit more information, our technical team are available to help. Just head over to our Contact Us page and drop in a question. Alternatively, you may find what you are looking for in our informative selection of blogs.
