When homeowners start researching what goes under a metal roof, two terms come up consistently: Anticon and sarking. They are both installed in roughly the same position in the roof system, they both contribute to moisture management, and they both appear in conversations about metal roofing insulation. But they are not the same product. They work differently, they address different primary problems, and knowing the difference matters when you are deciding what to specify for a roof replacement or asking the right questions of a contractor.
This guide gives you a direct, honest comparison of Anticon and sarking: what each one is, how each one works, what makes them different, and which is the right specification for a metal roof in Queensland.
What Is Anticon?
Anticon is an insulation blanket product specifically designed for installation under metal roofing. It consists of a layer of glasswool bulk insulation bonded to a reflective aluminium foil face. The glasswool provides thermal resistance by slowing conductive heat flow through the roof build-up. The foil face provides radiant heat reflection by directing infrared radiation away from the ceiling space below.
Anticon is installed directly beneath the metal sheeting, between the sheets and the battens below, with the foil face oriented downward toward the ceiling space. As well as its thermal performance, the glasswool layer absorbs condensation that forms on the foil surface overnight, preventing it from dripping into the ceiling space and causing the staining and structural damage that metal roof condensation causes in Queensland homes.
Anticon is the standard product specified under residential metal roofing across Queensland. It is not an optional upgrade. It is the correct insulation specification for metal roofing in a humid, high-UV, high-temperature climate.
Visit our Anticon blanket vs sarking guide for a detailed breakdown of both products from Fortified’s roofing specialists, drawing on over 50 years of Queensland installation experience.
What Is Sarking?
Sarking is a membrane product, not an insulation product. It is a flexible sheet material installed in the roof system, typically beneath the roofing surface, that serves as a secondary water barrier, a vapour management layer, and in the case of foil-faced products, a radiant heat barrier. Unlike Anticon, sarking does not provide meaningful bulk thermal resistance.
Sarking’s primary job is to manage water and vapour movement. If wind-driven rain gets past the primary roofing surface, sarking channels it to the eave rather than allowing it to drip into the ceiling cavity. Breathable sarking membranes allow water vapour to pass through in one direction while preventing liquid water from passing through in the other, which helps manage moisture levels in the roof cavity. Reflective foil sarking provides a radiant barrier that contributes to thermal performance, but without a meaningful air gap on the reflective face its contribution to thermal resistance is limited.
For a complete explanation of how roof sarking works, the types available, and when it is required under Australian building codes, visit our roof sarking guide for Australian homes.
What Are the Differences Between Anticon and Sarking?
Product Type
Anticon is an insulation product with bulk thermal resistance. Sarking is a membrane product with primary functions in water barrier and vapour management. This is the most fundamental distinction: Anticon insulates, sarking membranes.
Thermal Performance
Anticon provides genuine R-value from its glasswool layer. Standard Anticon products range from around R1.3 to R2.5 and above depending on thickness. Sarking membranes have very low bulk R-value, typically below R0.5. Foil-faced sarking contributes to the total system R-value through radiant barrier performance when installed with an air gap, but this contribution is significantly lower than the R-value of Anticon.
Condensation Management
Anticon physically absorbs condensation through its glasswool layer. When moisture condenses on the foil surface facing the roof cavity, the glasswool holds it until conditions allow it to evaporate. This prevents dripping. Sarking manages condensation risk differently: either by reducing vapour movement to the cold surface (vapour barrier products) or by allowing vapour to escape before it accumulates to condensation levels (breathable membranes). Sarking does not absorb condensation the way Anticon’s glasswool does.
Secondary Water Barrier
Sarking provides a defined secondary water barrier function. This means that if wind-driven rain or water from a tile or sheet lap failure penetrates the primary roofing surface, the sarking layer intercepts it and redirects it to the eave. Anticon is not designed as a secondary water barrier. Its foil face is not intended to be the primary waterproofing layer for a failed roofing surface.
Typical Applications
Anticon is predominantly used under metal roofing, particularly in residential applications across Queensland. It is the standard specification for Colorbond and Zincalume roof replacements. Sarking is used across both tile and metal roofing. In tile roof applications, sarking is the primary underpayment product, providing the secondary water barrier beneath the tiles. In metal roofing, it may be used in specific engineering-specified build-ups, particularly in high wind-driven rain exposure locations or commercial applications.
Installation Timing
Both products must be installed during a roof replacement or re-roofing project. Neither can be retrofitted to a fully installed roof without removing and reinstalling the sheeting or tiles above them. This is why the correct specification at the time of a roof replacement is important: there is no simple way to add either product to an existing installed roof without significant additional work.
We specify and install Anticon as standard on every metal roof replacement. If you are also replacing your gutters at the same time, visit our gutter replacement Brisbane page to understand how we coordinate the full system upgrade.
Which One Should You Specify for a Metal Roof in Queensland?
For residential metal roof replacements in Queensland, Anticon is the correct primary specification. The reasons are practical and grounded in Queensland’s specific climate conditions.
Queensland’s combination of high humidity, significant day-to-night temperature swings, and intense summer solar radiation creates conditions where both thermal performance and condensation management under the metal sheeting are genuinely important. Anticon addresses both with a single product: its glasswool provides meaningful thermal resistance that reduces heat transfer from the roof surface into the ceiling space, and its glasswool simultaneously absorbs condensation that forms on the foil face during cool, humid nights.
Sarking alone would provide the secondary water barrier and vapour management properties but would not deliver adequate thermal resistance or condensation absorption for Queensland’s conditions.
When Might Sarking Also Be Used Alongside Anticon?
In specific engineering-specified build-ups, particularly for commercial metal roofing applications, high wind-driven rain exposure locations, or roofs where the overall system is designed to a higher performance specification, both Anticon and a separate sarking membrane may be used together. In residential applications, this combined specification is less common. The decision is made during the project assessment based on the specific location, roof configuration, and performance requirements.
For Tile Roofing
For tile roofing, sarking is the standard underpayment specification rather than Anticon. Sarking beneath tiles provides the secondary water barrier function that is the primary requirement in a tile roof application, and a separate insulation layer (typically ceiling batts) addresses the thermal performance requirement at ceiling level. Anticon is a product specifically designed for installation beneath metal sheeting; it is not typically specified for installation directly beneath tiles.
If you are converting from a tile roof to a metal roof, our re-roofing Brisbane service includes a full specification review covering insulation, sarking requirements, ventilation, and all compliance obligations for your specific project.
What Should You Check When a Contractor Proposes an Insulation Specification?
- Is Anticon included in the quote as a standard line item, or is it treated as an optional extra?
- What is the R-value of the Anticon product being proposed?
- Is a separate sarking layer also being specified, and if so is the reason clearly explained?
- Does the overall roof build-up specification meet the NCC energy efficiency requirements for your Queensland climate zone?
- How are penetrations, laps, and joins detailed to maintain the continuity of the insulation and any sarking layer?
A contractor who treats Anticon as an optional cost item on a metal roof replacement in Queensland is not proposing a complete, correctly specified installation. Anticon is not an upgrade. It is a standard component of every correctly installed metal roof in Queensland.
Our team discusses the insulation specification for every project during the initial inspection and includes it clearly in the written quote. Visit our metal roofing Brisbane page for more information on how we approach complete metal roof specifications.
Works Cited
Fortified Roofing Group. “Anticon Blanket vs Sarking: What Should You Use Under an Australian Roof?” Fortified, 2026, fortified.com.au/anticon-blanket-vs-sarking/.
Fortified Roofing Group. “Roof Sarking Guide for Australian Homes.” Fortified, 2026, fortified.com.au/roof-sarking-guide-for-australian-homes/.
Fortified Roofing Group. “Roof Insulation Brisbane.” Fortified, 2026, fortified.com.au/roof-insulation-brisbane/.
Fortified Roofing Group. “Metal Roofing Brisbane.” Fortified, 2026, fortified.com.au/metal-roofing-brisbane/.
Fortified Roofing Group. “Re-Roofing Brisbane.” Fortified, 2026, fortified.com.au/re-roofing-brisbane/.
Fortified Roofing Group. “Gutter Replacement Brisbane.” Fortified, 2026, fortified.com.au/gutter-replacement-brisbane/.
