A question we often get asked by many of our clients is ‘don’t flat roof’s leak’? We believe that there is still a misconception that flat roof’s are typical of old shed felt roof’s which perish, leak and create damp and uninviting spaces. Fortunately, this is not the case and products available today not only provide exceptional weather protection but also aesthetically pleasing coverings, that can be utilised as architectural features, which is why so many designs look to create a flat roof that is not only visible but in some cases accessible.
Whilst the term ‘flat roof’ covers multiple products and manufacturers, the reality is that flat roof’s aren’t actually completely flat! they need a slope to allow water to be channelled away from the building to a designed water outlet/drainage system. Any roof designed under a 10 degree pitch falls under a flat roof category.
So, what flat roof coverings are available, and what are the pro’s and con’s of the products on the market today?
Torch-on materials
Materials such as felt, and bitumen fall under this category. Usually applied over a timber roof sheeting, such as chipboard or WPB (weather and boil proof) ply boards, the products are blowtorched in order to generate heat and to melt the products together at the joints, thus welding the materials together. Through the cooling down process, the roof product adheres and attaches itself to the timber sheeting and creates a watertight seal.
Modified bitumen is one of the most common materials installed this way. The asphalt-based covering is strong and durable, with a potential lifespan of around 20 years.
Despite being less robust and requiring periodic maintenance, felt is commonly used on domestic projects, felt and bitumen coverings offer value for money with a longstanding tradition.
Synthetic roofing
An alternative to torch on roofing is a single ply membrane, which is proven to be a durable and flexible covering, made predominantly from synthetic polymers. Popular options include PVC (Polyvinyl chloride), TPO (Thermoplastic polyolefin) and EPDM (ethylene propylene diene terpolymer). EPDM is essentially a sheet of manmade rubber (rubber roof) glued to a clean roof deck, which comes in two main thickness. When in place, the surface is smooth and robust and provides a rubber like appearance.
PVC roofing typically comes in sheet form, too. It’s a strong and lightweight material, with a good lifespan of around 20 years. This comes in a larger range of profiles, so it can be easier to manipulate and apply than EPDM materials. PVC tends to be a low cost solution for sheet roofing.
Whilst EPDM (rubber) roof’s are a common flat roof type, the covering is like rubber and therefore tends to be more commonly used on non-trafficked areas, which avoids the potential to puncture the top coat.
TPO membranes are a good modern option for flat roofs, especially as an alternative to lead. TPO is chemically welded using solvents and once sealed it stays sealed.
All products should be installed by professionals and come complete with insurance backed guarantee
Typical manufacturers of membrane roof’s:
Sika Sarnafil PVC products include Sarnafil Roof Membrane and Sikaplan Roof Membrane.
For a useful guide on how to install a rubber roof refer to Permaroof.
GRP
For use where foot traffic may be necessary, such as a roof terrace, a glass reinforced plastic (GRP) roof is often the ideal choice. Products come with multiple colour options and provide an appealing flat roof solution. GRP is a very durable product and relatively easy to apply to a structural deck, however it can only be applied to oriented strand board (OSB) and therefore, this will need to be factored into the design and on-site installation by the contractor.
Green roof/Sedum roof
The use of green roofs, or sedum roof’s, and installing a plant eco system on a flat roof, is becoming an ever poplar choice, especially for new build developments. One of the main benefits of this kind of covering, is it’s ability to remove air contaminants from the surrounding atmosphere. It also boasts minimal maintenance once installed, providing access to sun light and water is maintained.
Whilst most roof coverings work under the proviso of removing water as soon as possible off the roof, a green roof works in the opposite way, by retaining water for the growing process. All sedum and green roof’s must be fully installed by a professional, and must be complete with insurance backed guarantees. In addition, if a green roof is to be used, it must be considered early in the design stage, as the roof structure and its components must be designed to take the additional loads. There must be a minimum of 50mm deep substrate for the sedum to grow successfully and some kind of storage element for water within the dryer seasons.
Standing Seam roof
These roof systems are made up of metal sheets joined together by a crimping technique, which forms a seam otherwise known as a ‘zip roof’. The use of a standing seam roof allows designers and clients alike to utilise the use of materials such as zinc and aluminium. Whilst zinc has its architectural merits, it does come at a cost, which is roughly twice the price of aluminium sheeting. Standing seam roofs are extremely durable with lifespans in excess of 50 years. Whilst a standing seam roof is the more expensive option, it allows self builders, designers and clients the freedom to customise their property and create that ‘one off’ stand out property.
We have recently introduced an aluminium standing seam roof to one of our new build and refurbishment projects, for more information see our project here.
Flat roof advantages:
• Potential for lower roof levels (depending upon design).
• Contemporary look.
• Can provide cheaper build costs.
• Allows for the use of roof lanterns, creating enhanced natural daylight and providing an internal focal point.
• Less time consuming to construct equaling to quicker build times.
• Flexibility in roof coverings to suit aesthetics and budgets.
• Allows for existing ceiling heights to run flush within an extension, providing continuity between existing and extended areas.
• If your site is restricted on size, a flat roof extension creates the potential to increase outdoor living space by creating a balcony/veranda.
Thinking of starting your own new build or similar project? Check out our portfolios below.
New Build Portfolio
Extension & Renovation Portfolio
Instagram Page
