Install flat roofs the correcticel way.
Flat roof insulation boards
Building, refurbishing, or retrofitting a flat roof deck? Do it the correcticel way.
Flat roof construction requires specialised insulation boards to support energy efficiency, minimise heat loss, and maintain durability in both new builds and refurbishment projects.
Get flat roof insulation right
When you choose Recticel, you're choosing quality – our insulation boards are extremely robust and will last for decades to come.
Retrofitting flat roof insulation is difficult, messy, and time-consuming. You may also have to remove the existing waterproof layer. So we'd always recommend getting it right the first time.
The insulation boards for flat roofs
We're guaranteed to have the perfect insulation solution for every flat roofing application.
Our flat roof insulation boards meet the very highest standards for durability, compressive strength, and thermal performance. By preventing moisture build-up and condensation, they'll also help prolong the life of your roof.
💡 Warm roof vs cold roof. What's the difference?
➡ Warm roof deck construction
Warm roof deck construction is the UK's preferred choice for homes.
Some of our insulation boards are designed for warm roofs, where insulation is placed above the timber deck and below the waterproof membrane, protecting against rain, wind, and temperature extremes. Warm roof decks also typically include a vapour control layer beneath the insulation.
As the name suggests, warm roof deck construction keeps the deck void at a similar temperature to the roof, eliminating the need for ventilation by reducing condensation risk, while also minimising heat loss, improving energy efficiency, and lowering heating bills.
➡ Cold roof deck construction
Cold roof deck construction is less common and mainly used in refurbishment projects.
With cold roof decks, insulation is installed below the deck, between the timber joints at ceiling level. As such, there's no need to replace the existing waterproof layer or raise the roofline, assuming the deck's structural integrity is intact.
Cold roof decks are at greater risk of condensation since void temperatures are colder than the room below, which can lead to moisture damage. However, they also typically have lower installation costs, take up less space, better support foot traffic, and are well-suited for outbuildings.
Our handy calculator tool can get the U-value you need in seconds.
Get prepared for your next project and try our free-to-use online U-value calculator now!
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FAQs
Vacuum insulation
Can I use Vacuum Insulation Panels (VIP) in a tapered flat roof solution?
Yes, this is possible and recommended. We always advise a slope towards the outlets to ensure an adequate water drainage to avoid water stagnation on the roof.
There are generally two ways to approach this with Deck-VQ®:
- The fall is incorporated in the substrate (screed layer): in this case the Deck-VQ® boards will follow the existing fall.
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The fall is incorporated in the insulation layer: in this case Deck-VQ® can be combined with our tapered insulation* boards (Powerdeck® F or Eurothane® Eurodeck) on top. Our technical service with specialized tapered design service then provides an easy-to-use design for both insulation layers.
*Tapered insulation incorporates the slope over the length of the panel. Therefore, the panels can be installed on a flat surface, tightly jointed whilst resulting in a sloped top surface. Tapered insulation presents the ideal solution for a technically correct and thermally optimal build-up.
Contact our vacuum insulation specialist
Construction law & regulations
Can insulation be placed between and over flat roof joists?
BS 5250:2011, the British Standard for the control of condensation in buildings, does not recommend installing insulation between timber joists as well as above the deck.
However, not all hybrid roofs will show condensation risk, our Technical Services team will be happy to assist with U-value calculations and condensation risk analysis where required, we will also discuss the potential risks involved, but please note all calculations will be marked “NOT RECOMMENDED” inline with the British Standard.