Thermoguard Fire Varnish is a professional-grade clear intumescent varnish system designed for protecting timber and timber-based surfaces to BS Class 1, Class 0 and BS EN Class B s2 d0. When applied as a system with either the interior or exterior overcoat, it provides robust flame resistance, a durable finish and an aesthetically pleasing clear or stained look.

Ideal for new or bare internal wood, the system enhances natural wood grain while safeguarding surfaces against fire, heat and smoke. The Fire Varnish Basecoat intumesces under heat, forming an insulating char barrier. It is finished with either the Interior or Exterior Fire Varnish Overcoat which protects against UV, wear and cleaning.

Suitable for:

• Bare wood and previously varnished surfaces (with proper prep)

• Interior wood including ceilings, panelling and walls

• Exterior wood (with appropriate overcoat and full sealing)

• Not for use on floors or heavily trafficked surfaces

Available in 20m² packs.

Surface Preparation

• Ensure wood is dry (max 18% moisture), clean and free from wax, grease or other contaminants.

• Previously varnished surfaces must be abraded to provide a key.

• For OSB or other chipboards, test for cissing; degrease if needed.

• Fill gaps with Thermoguard Intumescent Mastic and seal rear faces of external wood.

Technical Data

Directions for Use

1. Mix the 2-pack basecoat and allow to stand 30–60 mins before use. Use within 4 hours.

2. Apply 1 coat of Fire Varnish Basecoat to dry wood.

3. Allow to dry overnight (min 8 hours) and hard dry before overcoating.

4. Within 4 days, apply 1 or 2 coats of Fire Varnish Overcoat:

   • 1 coat for clear interior finish

   • 2 coats for woodstain or exterior use

5. Ensure correct coverage rate as specified on the can.

6. Clean tools immediately with water after use.

Data Sheets 

Thermoguard Fire Varnish Overcoat Interior - TDS

Thermoguard Fire Varnish Overcoat Interior - MSDS