Description
Thermoproof Interior Fluid
Thermoguard Thermoproof Interior Fluid is a clear, colourless penetrating fire retardant treatment designed for porous internal timber and softwood surfaces.
Unlike traditional surface coatings, Thermoproof Interior Fluid penetrates deep into the timber itself. During fire exposure, the treatment reacts within the wood cells to help create a flame and heat resistant barrier that slows combustion and reduces flame spread.
The clear finish allows timber to retain its natural appearance, making it ideal for projects where decorative woodgrain needs to remain visible while improving fire performance.
What It Does
- Penetrates deeply into porous timber surfaces.
- Helps reduce flame spread through treated wood.
- Creates a heat resistant barrier during fire exposure.
- Preserves the natural appearance of timber.
- Provides clear fire protection without opaque paint finishes.
Why Choose Thermoproof Interior Fluid?
- Natural timber appearance: protects wood without covering grain beneath thick paint systems.
- Deep penetrating protection: works within the timber structure itself rather than sitting only on the surface.
- Simple application: suitable for brush, roller or spray use.
- Water-based formula: low odour, non-flammable and easier to work with internally.
- Ideal for visible timber: suitable for architectural wood features where appearance matters.
Where It Can Be Used
- Internal softwood timber
- Timber wall panelling
- Wooden ceilings and beams
- Joinery and timber features
- Decorative timber walls
- Timber furniture and fittings
- Porous untreated timber surfaces
Ideal For
- Hotels and hospitality interiors
- Schools and colleges
- Commercial refurbishment projects
- Public buildings
- Architectural timber interiors
- Heritage timber restoration
- Residential timber features
Fire Performance
- Tested to BS EN Class B s2 d0 standards.
- Achieves Class 0 surface spread of flame classification.
- Achieves Class 1 fire performance.
- Designed to help reduce flame spread and heat release on timber surfaces.
- For 30 or 60 minute systems, refer to Thermoguard Fire Varnish system specifications.
How It Works
- The fluid penetrates into the timber fibres and wood cells.
- Under fire exposure, the treatment reacts internally within the wood structure.
- A flame and heat resistant barrier forms within the timber.
- This helps slow ignition, combustion and flame spread.
- The treatment works without creating a thick visible surface layer.
Application Information
- Apply by brush, roller or spray.
- Typically applied as a one coat penetrating treatment.
- Apply only to dry timber below recommended moisture levels.
- Allow the treatment to fully penetrate and dry before sealing or overcoating.
- Always test on a small area before full application.
Optional Sealer Finishes
- Can be left as a bare treated timber finish.
- Optional Thermoproof Interior Sealer available for added durability.
- Sealer available in clear or woodstain finishes.
- Suitable where additional resistance to wear, damp or light cleaning is required.
Coverage Guidance
- Available in 20m² and 80m² treatment pack sizes.
- Coverage varies depending on timber porosity and texture.
- Rough sawn timber absorbs significantly more fluid than smooth planed timber.
- Correct application rates are essential for certified fire performance.
Surface Preparation
- Timber must be bare, porous and capable of absorbing the treatment.
- Painted, sealed or waterproofed surfaces will prevent penetration.
- Previously varnished or coated timber may require complete removal of existing finishes.
- Apply only to dry timber with moisture content typically below 16%.
- Always carry out a test patch before treating the full project.
Good To Know
- This product is intended for porous internal timber and softwood only.
- It will not perform correctly on sealed, painted or waterproofed wood.
- Thermoproof Interior Fluid does not itself provide 30 or 60 minute fire resistance.
- For higher fire resistance systems, use Thermoguard Fire Varnish systems instead.
- Certificates of Supply may be available for qualifying projects following correct application.
Need Fire Protection Without Covering Natural Timber?
Many fire protection systems completely hide the beauty of timber beneath heavy opaque coatings. Thermoproof Interior Fluid is designed for projects where retaining the natural appearance of wood is just as important as improving fire safety performance.
Need Help Choosing The Correct Timber Fire Protection System?
Different timber types, finishes and fire performance requirements may require different Thermoguard systems. If you are unsure whether Thermoproof Interior Fluid is suitable for your project, contact the technical team before ordering.
Technical Support: 01142 768008
Email: technical@thermoguard.co.uk
