Liquid Membranes for Timber Frame Construction

Liquid Membranes for Timber Frame Construction

Achieve reliable airtightness and vapour control in open-panel and closed-panel timber frame buildings — spray or brush applied, no overlaps, no weak points.

Passive Purple External spray-applied airtight membrane on a timber frame building for waterproofing and energy efficiency

Why Airtightness is Critical in Timber Frame

Timber frame buildings are fast to erect and thermally efficient — but they are inherently vulnerable to airtightness failure if the membrane strategy isn't right. Joints between panels, service penetrations, window reveals and wall–floor junctions are the most common failure points, and traditional sheet membranes rely on overlapping, taping and detailing that is difficult to execute consistently at speed on a busy site.

Intelligent Membranes liquid-applied products eliminate these failure points by forming a seamless, continuous airtight layer across the entire substrate — bridging joints, following complex geometry, and sealing penetrations without any laps, primers or tapes.

Common Challenges — and How We Solve Them

⚠️ Challenge: Panel joints and junctions are time-consuming to tape correctly, and tape failures are only discovered at the blower door test.
✅ Solution: Passive Purple Brush is fibre-reinforced and bridges panel joints up to 2–5mm. Apply before the spray coat for a guaranteed sealed joint with no tape skill required.
⚠️ Challenge: Service penetrations (pipes, cables, MVHR ducts) are notoriously difficult to seal with tape-based systems, especially in retrofit or at high density.
✅ Solution: Passive Purple Brush applied around penetrations provides a flexible, permanent seal on any substrate — including rough-sawn timber, OSB, brick and blockwork. No primer needed.
⚠️ Challenge: Large floor areas take days to tape with sheet membranes. Spray application of liquid membranes is significantly faster and leaves fewer potential failure points.
✅ Solution: Passive Purple Internal (spray grade) allows one operative to cover up to 300m² per day with an airless spray machine — dramatically reducing programme time vs sheet membranes.

3D cross-section of a timber frame wall and floor junction showing Passive Purple External on the facade and Passive Purple Internal on the warm side

Recommended Products for Timber Frame

Product Where Used Why
Passive Purple Internal (Spray) Internal faces of walls, floors, ceilings Fast 300m²/day coverage; Passivhaus certified; seamless VCL & airtight layer
Passive Purple Brush Joints, junctions, penetrations, reveals Fibre-reinforced; bridges cracks up to 5mm; ideal for all critical details
IM Passivhaus Sealant Panel perimeter sealing and gap-filling Flexible Passivhaus-certified sealant for movement joints and connection sealing
IM Fleece Tape Membrane-to-frame transitions For areas where tape is preferred alongside the liquid system
Passive Purple External External face of frame (where specified) External airtight, weatherproof and fire-rated facade membrane

Performance Standards Achievable

Part L 2021 — ≤5 m³/h·m² @ 50 Pa

The minimum UK Building Regulations standard for new dwellings. Routinely achieved with Passive Purple on timber frame.

NHBC / Structural Warranty — ≤8 m³/h·m²

Passive Purple comfortably meets NHBC and other structural warranty airtightness requirements.

Passivhaus Classic — ≤0.6 ACH @ 50 Pa

Passivhaus Institut certified product, with verified test results on timber frame construction achieving Passivhaus levels.

EnerPHit Retrofit Standard

Passive Purple Retrofit is suitable for EnerPHit refurbishment projects on existing timber frame structures.

Completed energy-efficient timber frame home with a Passive Purple airtight and waterproof building envelope

Suitable Construction Types

  • Open-panel timber frame (stud and rail, platform frame)
  • Closed-panel timber frame (factory-insulated panels)
  • Structural Insulated Panels (SIPs)
  • Cross-laminated timber (CLT)
  • Traditional cut timber roofs and floors
  • Timber frame retrofit and over-cladding

Get Technical Support for Your Timber Frame Project

Our team can advise on product selection, coverage quantities, junction detailing and airtightness strategy — free of charge.

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