Roof blanket and sarking are two terms that often appear in the same conversations about metal roofing, sometimes used as though they are the same product and sometimes as though they are completely unrelated. The confusion is understandable because both products sit in the roof system between the metal sheeting and the structure below, and both contribute to moisture management and thermal performance. But they are different products that work in different ways and serve different primary purposes.
This guide explains what roof blanket and sarking each are, how they work, what makes them different, when each one is appropriate, and how to think about whether you need one or both for a Queensland home.
What Is Roof Blanket?
Roof blanket is the common name for Anticon insulation blanket, a product widely used in Australian metal roofing. It is an insulation product: a layer of bulk insulation material, most commonly glasswool fibre, bonded to a reflective aluminium foil face. The blanket is installed between the metal roofing sheeting above and the battens below, sitting in direct contact with the underside of the metal sheets.
The foil face is oriented downward, toward the ceiling space, where it reflects radiant heat away from the living areas below. The glasswool layer provides thermal resistance against conductive heat transfer through the roof build-up, and also absorbs any condensation that forms on the foil surface before it can drip down into the ceiling space. This dual action, thermal insulation and condensation absorption, is what makes Anticon the standard specification for metal roofing in Queensland.
Roof blanket is primarily an insulation product with secondary moisture management properties. Its R-value, the measure of its resistance to heat flow, is its defining performance characteristic.
Anticon is included as a standard component of all metal roof replacements we carry out. Visit our roof insulation Brisbane page for detailed information on the Anticon products we specify and install.
What Is Sarking?
Sarking is a membrane product, not an insulation product. It is a flexible sheet material installed beneath the roofing surface, typically between the tiles or metal sheets and the battens below. Unlike roof blanket, sarking does not provide significant bulk thermal resistance. Its primary roles are as a secondary water barrier, a vapour management layer, and in the case of reflective foil products, a radiant heat barrier.
Sarking acts as a last line of defence if water penetrates the primary roofing surface. Wind-driven rain that forces its way past tile laps or metal sheet joins during a storm event meets the sarking layer, which channels it to the eave rather than allowing it to drip into the ceiling space. Sarking also contributes to reducing the movement of air, dust, and moisture between the outside environment and the roof cavity.
Foil-faced sarking products include a reflective aluminium surface that reflects radiant heat. When installed with an appropriate air gap on the reflective face, this provides a meaningful reduction in heat transfer from the roof surface into the ceiling space, though the R-value contribution of sarking alone is low compared to Anticon.
For a comprehensive explanation of what sarking is, how it is installed, and when it is required under Australian building regulations, visit our roof sarking guide.
What Are the Key Differences Between Roof Blanket and Sarking?
Primary Function
Roof blanket (Anticon) is primarily an insulation product. Its defining purpose is to provide thermal resistance and absorb condensation. Sarking is primarily a membrane product. Its defining purpose is to provide a secondary water barrier and vapour management layer. While both products contribute to moisture management and thermal performance, their primary functions are different.
Thermal Performance
Roof blanket provides meaningful bulk thermal resistance (R-value) because of its glasswool layer. The R-value of a standard Anticon blanket ranges from around R1.3 to R2.5 or higher depending on the product specification. Sarking alone provides very low bulk R-value, typically below R0.5, though it contributes to the overall roof system thermal performance through its radiant barrier effect when installed with an air gap.
Condensation Management
Anticon’s glasswool layer directly absorbs condensation that forms on the foil surface, preventing it from accumulating and dripping. This is a physical absorption process. Sarking manages condensation differently: depending on the product type, it either acts as a vapour barrier that reduces the movement of moist air to the cold surface in the first place, or as a breathable membrane that allows vapour to escape in one direction while preventing liquid water from passing through in the other. Sarking does not physically absorb condensation the way Anticon does.
Installation Position
Both products are installed between the roofing surface and the structure below. In practice, when Anticon and sarking are used together in a metal roof system, Anticon sits directly beneath the metal sheeting, with the foil face down, and any sarking layer sits below it. The positions are determined by the engineering specification for the specific roof build-up.
Applications
Anticon is predominantly used in metal roofing applications across Queensland and is the standard insulation product for residential metal roof installations. Sarking is used in both metal and tile roofing applications and is the more common product in tile roof applications where its secondary water barrier function is the primary requirement. In commercial metal roofing, specific sarking or membrane products may be used as part of a more complex engineered build-up.
Do You Need Both Under a Metal Roof in Queensland?
For most residential metal roofing applications in Queensland, Anticon alone is the primary product specified and installed. It delivers both the thermal insulation required to meet energy efficiency provisions and the condensation management required for Queensland’s humid climate. Anticon is the standard, and a correctly specified Anticon layer in a well-ventilated roof with good vapour management between the living areas and the ceiling space delivers excellent performance.
There are specific circumstances where a separate sarking layer may be used alongside Anticon, or where a particular sarking product may be specified instead of or in addition to Anticon.
When Both May Be Used Together
On roofs in locations with very high wind-driven rain exposure, where the secondary water barrier function of sarking is an additional safeguard, a combined build-up of Anticon with a separate sarking membrane below it may be specified by the engineer. In commercial roofing applications with specific hydraulic performance requirements, more complex build-ups that include both products are sometimes used. And on tile roofs converting to metal, there may be situations where the existing sarking layer under the tiles is retained or replaced as part of the conversion, while new Anticon is installed under the new metal sheeting above.
When Anticon Alone Is Sufficient
For the large majority of residential metal roof replacements across Queensland, Anticon is the correct and complete insulation and moisture management specification. A quality Anticon product installed by an experienced contractor, combined with adequate roof space ventilation and correct installation detail at laps and penetrations, meets the functional requirements of the installation.
The correct specification for your specific roof, location, and build-up is confirmed during the inspection process. Visit our Anticon blanket vs sarking guide for a direct comparison of both products from Fortified’s roofing experts.
What Should You Ask Your Contractor About Insulation Under a New Metal Roof?
When getting quotes for a metal roof replacement, the following questions help you understand whether the insulation specification is correct.
- Is Anticon insulation included in the quote, and what is the R-value of the product being specified?
- Is Anticon included as a standard part of the scope or is it quoted as an additional item?
- Is a separate sarking layer being specified, and if so why and what product?
- How is the Anticon installed: is it lapped correctly at all joins, and how are penetrations handled?
- Does the specification meet the NCC energy efficiency requirements for the relevant Queensland climate zone?
A contractor who does not include Anticon as a standard part of a metal roof replacement quote in Queensland is missing one of the most important components of a correctly specified installation. This is a question worth raising directly.
We include Anticon as standard in every metal roof replacement we carry out across Brisbane, the Gold Coast, Ipswich, Logan City, and the wider Southeast Queensland region. Visit our metal roofing Brisbane page or contact our team to discuss what is included in a full project specification.
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 Insulation Brisbane.” Fortified, 2026, fortified.com.au/roof-insulation-brisbane/.
Fortified Roofing Group. “Roof Sarking Guide for Australian Homes.” Fortified, 2026, fortified.com.au/roof-sarking-guide-for-australian-homes/.
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. “What Causes Metal Roof Condensation and How Can You Fix It in Australia?” Fortified, 2026, fortified.com.au/metal-roof-condensation/.
