Description
Thermoproof Exterior Fluid
Thermoguard Thermoproof Exterior Fluid is a deep penetrating fire retardant treatment designed for porous bare exterior timber including cladding, fencing, decking, sleepers and exposed wood structures.
Unlike surface-only coatings, Thermoproof Exterior Fluid penetrates deep into the timber structure itself. During fire exposure, the treatment reacts within the wood to form an insulating inert layer that helps reduce flame spread and slow combustion.
The clear water-based formula allows timber to retain its natural appearance while adding tested fire retardant performance suitable for a wide range of external timber applications.
What It Does
- Penetrates deep into porous exterior timber.
- Helps reduce flame spread through treated wood.
- Creates an insulating inert layer during fire exposure.
- Provides clear fire protection without hiding natural timber grain.
- Suitable for external and internal porous timber applications.
Why Choose Thermoproof Exterior Fluid?
- Natural timber appearance: protects wood without covering it beneath opaque paint systems.
- Deep penetrating protection: works within the timber structure rather than sitting only on the surface.
- Exterior durability: weather resistant formulation designed for exposed timber environments.
- Water-based technology: non-flammable, lower odour and easier to apply.
- Suitable for large timber areas: ideal for cladding, fencing and external architectural timber.
Where It Can Be Used
- Exterior timber cladding
- Fencing and gates
- Decking and boardwalks
- Timber sleepers
- Garden buildings and sheds
- Exterior timber façades
- Porous internal timber surfaces
Ideal For
- Architectural timber cladding projects
- Commercial timber developments
- Public buildings and schools
- Hospitality and leisure environments
- Residential timber features
- Landscaping and timber structures
- Timber refurbishment projects
Fire Performance
- Tested to BS EN Class B s2 d0 standards.
- Achieves Class 0 surface spread of flame classification.
- Achieves Class 1 fire performance.
- Can contribute toward 30 or 60 minute fire resistance within specified systems.
- Designed to reduce flame spread and heat release on timber surfaces.
How It Works
- The fluid penetrates deeply into porous timber fibres.
- Under fire exposure, the treatment reacts within the timber structure.
- An insulating inert layer forms inside the wood surface.
- This helps slow flame spread and reduces the speed of combustion.
- The treatment works without creating a thick visible surface film.
Application Information
- Apply by brush, roller or spray.
- Normally applied in 3 coats on porous timber.
- Very rough sawn timber may allow 2 heavier coats.
- Allow each application to fully soak into the timber before recoating.
- Apply only to dry timber in suitable weather conditions.
Coverage Guidance
- Typical application rate is approximately 3.5m² per litre.
- Coverage varies depending on timber porosity and surface texture.
- Rough sawn timber absorbs significantly more fluid than planed timber.
- Correct application rates are essential for certified fire performance.
Surface Preparation
- Timber must be bare, porous and capable of absorbing the treatment.
- Remove paints, sealers, waxes and waterproof coatings before application.
- Previously waterproofed timber may prevent penetration and reduce effectiveness.
- Apply only to dry timber below recommended moisture levels.
- Always apply a small test area before large-scale treatment.
Appearance & Finish
- Clear and colourless finish.
- Allows timber to weather naturally.
- Maintains visible timber grain and character.
- Can be overcoated with suitable breathable systems where specified.
Good To Know
- This product is designed for porous bare timber only.
- It will not perform correctly over waterproof or sealed surfaces.
- Coverage rates are critical to achieving certified fire performance.
- External timber should be maintained appropriately depending on exposure conditions.
- Thermoguard can provide Certificates of Supply for qualifying projects.
Need Fire Protection Without Hiding Natural Timber?
Many exterior fire protection systems cover timber beneath thick paint layers that completely alter its appearance. Thermoproof Exterior Fluid is designed for projects where retaining the natural look of timber is just as important as improving fire performance.
Need Help Specifying Exterior Timber Fire Protection?
Different timber species, surface textures and environments absorb fire retardant treatments differently. If you are unsure whether Thermoproof Exterior Fluid is suitable for your project, contact the Thermoguard technical team before ordering.
Technical Support: 01142 768008
Email: technical@thermoguard.co.uk
