Thermoguard Fire Varnish Overcoat Exterior is a professional-grade clear lacquer designed for use over Thermoguard Fire Varnish Basecoat to protect timber and wood-based substrates in external environments. This solvent-based topcoat forms a tough, UV-resistant finish that enhances the appearance of natural or stained wood while contributing to fire protection systems tested to BS EN Class B s2 d0.

Ideal for applications where a durable, weather-resistant finish is required, it provides reliable performance as part of a complete fire varnish system. Use over basecoat to complete certification-ready, flame-retardant systems for cladding, paneling, soffits and more.

Surface Preparation

• Ensure surfaces are clean, dry and free from contamination.

• Wood must be fully dry with no more than 18% moisture content.

• Fill joints and gaps with Thermoguard Intumescent Mastic.

• Abrade existing sealed or varnished surfaces to create a key.

• Refer to the Fire Varnish Basecoat TDS for base preparation

Technical Data

Specification Detail Finish Clear Matt or Satin Colour Options Clear or Woodstain Volume Solids Mixed product: 42–44% Mix Ratio 10:1 base:activator (by volume) Coverage Up to 10m² per litre (2 coats required for exterior use) Touch Dry 2 hours (min) Recoat Time 2–36 hours Pot Life 4 hours after mixing VOC Content High – solvent based Application Methods Brush, Roller, Conventional or Airless Spray Pack Sizes 20m² packs

Directions for Use

• Apply first coat at 60 microns wet (30 microns dry).

• Allow to cure for 2 hours minimum, then denib.

• Apply second coat 2–36 hours after first coat.

• If overcoating after 36 hours, abrade surface and allow to dry overnight before recoating.

• Use conventional pressure pot spray or airless spray (11 thou tip). Thin up to 10% with Thermoguard Spray Shop Lacquer Thinners if needed.

• Avoid contamination of basecoat.

• Ensure application is in dry conditions (min. 6°C air temp, 3°C above dew point).

• Max humidity 75%. Ensure good ventilation.

Data Sheets 

Thermoguard Fire Varnish Overcoat Interior - TDS

Thermoguard Fire Varnish Overcoat Interior - MSDS