Look at the wall section on a lot of project home plans and you'll see two words: "reflective wrap". No product name. No classification. No installation standard.
That vagueness matters. The membrane behind your cladding is part of what keeps water out of the frame, controls air leaks, lets moisture dry out and, if it's reflective, adds a little insulation value. Different membranes do these jobs differently. When the plans just say "reflective wrap", there's nothing specific to hold the builder to. And if problems show up years later, it's much harder to prove what was specified and installed.
C10 - Rough In Stage Inspection Checklist
$59.00 AUD
Last updated 5 Oct 2026 · Revision 1 · Free updates for life
Checklist Type: Minor
Form Factor: Fillable, print-ready PDF (A4, 25 pages)
When to use: Rough-in stage: after services are installed, before cladding and linings go on
A 200-point rough-in checklist. Check electrical, plumbing, gas, solar, membranes and air-conditioning ducts before cladding and linings hide them, while changes are still easy.
What "reflective wrap" could mean
Wall wraps are pliable building membranes, covered by AS/NZS 4200.1 (materials) and AS 4200.2 (installation). A wrap can be designed to do one or more of these jobs:
- Water control: resist liquid water that gets past the cladding.
- Air control: limit air leaking through the wall.
- Vapour control: let water vapour pass through, or slow it down. AS 4200.1 rates this from Class 1 (a vapour barrier, very little vapour passes) to Class 4 (highly vapour permeable).
- Thermal: a reflective (foil) face next to an air gap reduces radiant heat transfer.
"Reflective" only describes one of those properties, the foil face. It tells you nothing about the wrap's vapour class or how well it resists water. Two "reflective wraps" can behave completely differently in a wall.
Why the vapour class matters in Queensland
Water vapour moves from warm, humid air towards cooler, drier air. If it hits a cold surface inside the wall, it condenses, and you get mould, rotting timber, corroded fixings and wet insulation that doesn't work.
Much of the advice online comes from cold climates, where you put a plastic vapour barrier on the inside of the wall to stop warm indoor air reaching the cold outer layers. In a hot, humid Queensland summer with the air conditioning running, it's often the reverse: the humid air is outside and the cool surface is inside. Put plastic sheeting on the inside of an air-conditioned Queensland home and you can trap condensation in the frame.
That's why NCC 2022 introduced condensation management requirements. For external walls, the wall wrap's vapour permeance class has to suit the climate zone. In cooler climate zones (4 and 5, which include some upland parts of Queensland), a wrap on the outside of the insulation must be at least Class 3, and in zones 6 to 8 it must be Class 4. In hotter zones the NCC is less prescriptive, which makes getting the right advice for your wall even more important. NCC 2022 also requires exhaust fans to discharge outside, not into the roof space.
The point isn't that one class is always right. Where each layer goes, and which class it should be, depends on your climate zone and the wall design. Ask your designer to show it on the wall section drawing.
How vague specifications let builders off the hook
If your plans name a specific product with a known classification, there's a standard to check against: the manufacturer's installation instructions and AS 4200.2. Laps, tape, fixing and how it's dressed into window openings are all defined.
If the plans say "reflective wrap", the builder can install whatever was cheapest or on the truck that week, and claim they met the specification. Nobody can say it's wrong, because nobody said what was right.
The result can be a product that isn't suited to your climate, installed without the detailing that makes it work. Problems like mould or water damage often don't show up until well after handover.
What to ask your builder
Get the answers in writing, and make sure they appear in your contract documents.
- What's the product name? Not "reflective wrap" or "sarking". The actual product.
- What's its AS 4200.1 classification? Its vapour permeance class (1 to 4) and water resistance rating.
- Is it reflective? If so, is there a still air gap next to the foil face? Without a gap, the reflective face does nothing.
- Why is that class right for my climate zone and wall? A builder who has thought about it will have an answer.
- Is there a drained, vented cavity behind the cladding? This gives water a way out and lets the wall dry.
- How will joins, penetrations and window openings be lapped and taped?
- Has anyone checked the wall and roof for condensation risk? Read why your builder should be doing a condensation risk analysis.
Check it on site
Specification is only half the job. At frame stage, before the cladding goes on, check:
- The installed product matches what was specified.
- It's lapped the right way, with upper sheets over lower sheets, so water runs out and not in.
- Joins and penetrations are taped where the manufacturer requires.
- It's properly dressed and taped into window and door openings, and the flashings are in place.
- There are no tears, gaps or loose sections.
Our C7 Frame checklist walks you through what to look for. Take photos. Once the cladding is on, you'll never see it again. If you're not confident checking it yourself, an independent building inspector can do it for you.
Read more on installing wall wrap to Australian Standards and why your new home needs a rainscreen.
Don't accept vague
"Reflective wrap" isn't a specification. It's a placeholder. Ask for the product, the classification and the reason it suits your home, and check it's installed properly. Your walls have to stay dry for the next 50 years. They deserve more than two words on a drawing.
