Whether it’s a garage, garden room or small extension, flat roofs can be a common occurrence for builders and roofers alike. But how should you approach insulating it correctly?
Q) First of all, what are we classifying as a flat roof?
As per BS 6229, a flat roof is characterised by ‘a pitch less than 10° to the horizontal.’ However, it is commonly considered a flat roof if it has a pitch less than 15°.
While that’s the general rule of thumb, there are always exceptions; so, if you’re not sure, talk to your local planning officer or get some advice from an approved roofing installer.
If a flat roof is going to work, it needs to be able to drain rainwater effectively into the gutters. Otherwise, ponding water can lead to potential problems. Aside from the fact it won’t look great, performance issues can include silt deposits and freezing, a greater chance of water ingress and damp, odour and hygiene issues and of course the resulting maintenance costs to fix the problem.
Q) There are several types of flat roof construction, so which one is best?
Each method of creating a flat roof has its own pros and cons and there are a variety of insulation options to choose from. It's important to take some time to review the requirements to ensure that everything aligns with the job's needs. This will help you make informed decisions about what will be most effective.
Warm roof or built-up roof (BUR):
The insulation is positioned above the above the structural deck and Air Vapour Control layer, which contributes to the building's warm fabric. Additionally, it is placed directly beneath the waterproofing layer, enhancing the overall efficiency and protection of the structure.
Cold Roof:
This type of roof is no longer recommended unless absolutely unavoidable. This is due to the challenges in creating and maintaining an effective air and vapor control layer (AVCL) beneath the insulation, along with providing adequate cross ventilation above it (refer to BS 5250).
Q) What type of insulation board should I use for a flat roof?
While there are a variety of insulation products available on the market, if you want a solution that you know will do the job no matter what type of flat roof construction you’re dealing with, then our own Eco-range of flat roof boards are a practical choice for flat roofing jobs.
Eco-Torch is designed for compatibility with a wide range of applications, including torch-on and roll-and-pour felts, mastic asphalt, and fully adhered single-ply systems. When utilizing single-ply membranes, Eco-Torch should be installed with the fleece side facing down.
Eco-Bond is suitable for use with fully adhered and mechanically fixed waterproofing systems such as PVC, TPO, EVA, and EPDM. Additionally, Eco-Bond can be used with a, partially bonded built-up felt, and certain liquid-applied waterproofing systems.
Eco-Fix is designed for use with mechanically fixed waterproofing systems, including PVC, TPO, EVA, and EPDM.
Made from a durable PIR core, the Eco-range is thermally efficient, lightweight, easy to cut and install compared toother commonly used insulants. Crucially, they have the compressive strength you need to help avoid any damage during installation.
And finally, before you go…
Flat roofs can present a complicated task, with a variety of issues to consider – far more than we’ve explored in this blog today. However, its construction, efficient drainage and choice of weatherproofing system and insulation will all play a fundamental role in its long-term success and at the end of the day, your own professional reputation.