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Flat roofs are the most demanding surfaces to insulate — we design them not to fail. Every flat roof insulation project is modelled using WUFI® Pro or BuildDesk software, ensuring the complete build-up — membranes, substrates, foam thickness and environmental loads — is safe, compliant and long-lasting.
With limited pitch, exposure to extreme weather cycles, and the complexity of internal vapour drive, getting flat roof insulation wrong can lead to interstitial condensation, deck rot and hidden mould growth, sagging ceilings and wet insulation, and regulatory non-compliance and warranty issues.
At Duratite, we don’t just supply spray foam for flat roofs — we design them. Every project is modelled before a single litre of foam is proposed, and installation is carried out by our manufacturer-trained approved installer network.
The Duratite approach: science before spray. Before insulation is installed, we evaluate each project’s roof assembly for vapour diffusion resistance and permeability profiles, winter and summer dew point formation, risk of interstitial condensation or mould over time, air pressure zones and risk of windwashing, and the required U-value, service conditions and fire strategy.
Designed for maximum thermal resistance and vapour control. Because Nexseal LE is closed-cell, it prevents both air leakage and moisture ingress, supporting robust, long-life performance even in high-risk zones.
Used for breathable flat roof designs or in internal ceilings, paired with a suitable vapour control layer. A great option in timber-framed flat roof elements where breathability and sound absorption matter — its vapour-open nature means it must be correctly modelled for safe year-round performance.
Spray foam is a free-sprayed, self-adhering insulation that replaces traditional PIR boards, mineral wool or battens — removing the risk of gaps, joint shrinkage and cold bridging.
| Roof Type | Spray Foam Solution | Detail |
|---|---|---|
| Warm Roof (internal) | Nexseal LE | Applied under deck with plasterboard finish |
| Cold Roof (joist fill) | Sucraseal or Nexseal | Between joists + VCL + batten + board |
| Hybrid Roof | Nexseal LE partial fill | Deck insulation + vented airspace + joist layer |
| Solid Deck Retrofit | Nexseal LE | Sprayed onto concrete/steel soffit, internal ceiling finish |
| Compact Roof | Nexseal LE | Minimal depth, high resistance, underside spray |
| Flat Roof with Service Voids | Sucraseal | Acoustic + thermal layer between M&E zones |
Both Enverge foams are rated Euroclass E under EN 13501-1. To comply with fire safety regulations, spray foam must be covered by a suitable lining — or, where left partially or fully exposed (plant rooms, pod roofs, industrial ceilings), coated with DC315 intumescent coating applied to tested film thicknesses.
Duratite provides detailing support, specification advice, and on-site QA procedures to ensure full compliance and certification of both the foam and any fire-rated coatings.
Plasterboard lining12.5 mm or 2-layer plasterboard for inhabited spaces.
Cementitious boardWhere humidity resistance is needed.
Fire-rated voided ceilingsFor commercial roof zones.
DC315 intumescent coatingFor exposed foam — tested film thicknesses to Euroclass B-s2,d0.
Spray foam creates a monolithic thermal layer across even the most complex roof geometry.
Nexseal LE acts as its own vapour control layer. Sucraseal is modelled with membranes to manage vapour diffusion safely.
Low U-values with thinner layers than board systems — greater ceiling height and easier M&E coordination.
No mechanical fixings, no adhesive bonding — just direct spray to the roof structure for permanent adhesion.
Foam systems can contribute to sound reduction and be protected with DC315 where required.
Every roof is engineered for performance and durability — not just insulated.
At Duratite, every flat roof we insulate is accompanied by a full U-value calculation based on accurate layer thicknesses, a condensation risk analysis using I.S. EN ISO 13788 or WUFI® Pro, detailing support for vapour control and membrane placement, and advice on roof venting, fire protection and ceiling finish layers.
Technical resources available on request: Nexseal LE and Sucraseal datasheets, flat roof build-up guide, DC315 application sheet, vapour risk modelling summary, fire compliance and lining requirements, and the warm vs cold flat roof detailing pack.
Free technical advice · info@duratite.ie
Closed-cell spray foam applied between and under rafters — warm-roof performance on pitched roofs without losing headroom.
Learn more →WaterproofingGacoFlex silicone systems for flat roofs — seamless, ponding-water rated, 20-year manufacturer-backed product warranty.
Learn more →Spray Foam HubThe full range of Enverge spray foam applications Duratite supports across Ireland and Northern Ireland.
Learn more →From dormers and extensions to commercial soffits and modular roof cassettes, flat roofs demand attention to detail. With Duratite, you get scientific design modelling, manufacturer-trained approved installers, fire compliance planning with intumescent coatings, and full technical support, drawings and on-site guidance.
Tell us about your flat roof and we’ll model the right build-up — free, no obligation.
Mon–Fri 8am–5pm · info@duratite.ie
Real Duratite projects — building type, location, system used and the outcome on site.
Chiswick, London, EnglandResidential
Torquay, Devon, EnglandCoastal Flat RoofTell us about your building and we’ll recommend the right system — foam, waterproofing or both — surveyed, specified and quoted at no cost.
