Spray-Applied External Airtightness for Retrofit and Re-Cladding
When a building is being re-clad or externally upgraded, it’s the perfect moment to add a continuous airtight, weatherproof layer — fast, over large areas, and without trapping moisture in the existing structure.
Why re-cladding is the moment to act
Re-cladding exposes large wall areas briefly — the one time you can treat the whole envelope from outside without disrupting occupants. Adding airtightness now avoids ever having to go back inside, and lifts the building’s energy performance at the same time as its appearance and fire strategy.
The constraint: keep walls breathing
Sealing them by hand is too slow at this scale, and a non-breathable coating risks damp in the existing fabric. Retrofit guidance such as PAS 2035 makes moisture safety essential, so the membrane has to be vapour-open as well as fast to apply.
The solution: Passive Purple X (10kg Spray)
Passive Purple X (10kg) is a vapour-open airtight membrane with a Class B fire rating, sprayed or rollered across large external areas quickly. It seals against air and weather while letting walls breathe — ideal for retrofit and re-cladding behind a new rainscreen or render system.
How it is applied
- Prepare and prime the existing substrate as needed
- Detail junctions and penetrations with the brush grade
- Spray or roller the open areas to the required film thickness
- Install the new cladding or render over the cured membrane
Benefits
- Fast spray or roller coverage
- Vapour-open, Class B fire rating
- Airtight and weatherproof
Frequently asked questions
Does it suit high-rise re-cladding? Yes — it’s installed from the outside in, ideal where internal access is limited.
What about the details? Pair it with the 5kg brush grade for junctions and reveals.