Thermoguard Fire Varnish Basecoat
  • Thermoguard Fire Varnish Basecoat

Thermoguard Fire Varnish Basecoat


Thermoguard Fire Varnish Basecoat is a clear intumescent varnish that is the first coat of a 2 coat system (3 coats externally) for the decorative Fire Protection of timber and timber derived substrates to BS Class 1, Class 0 and EN Class B s2 d0. See Thermoguard Fire Varnish Overcoat (Exterior) to complete the system.

Complete systems including basecoat and overcoat can be found here;

VAT excluded

£123.60 Tax incl.


Clear Fire Protection Basecoat for Fire Varnish System for Wood

New 2020 Product Update - Improved Formula!

  • Simplified application - no requirement to add water prior to use
  • Lower odour

Thermoguard Fire Varnish is a clear varnish system for the Fire Protection of timber and timber derived substrates to BS Class 1 and Class 0 Surface Spread of Flame as well as BS EN Class B s2 d0 (for 30 or 60 minutes Fire Resistance see Thermoguard Fire Varnish 30 & 60 Minute System). The special formula provides a tough, durable finish to internal and external wood. The clear finish enhances the natural beauty of the wood while providing protection against UV and wear as well as fire protecting new and previously varnished surfaces.

The Thermoguard Fire Varnish System is made up of Thermoguard Fire Varnish Basecoat (a two component, water based product consisting of a base and activator mixed together before use - see image above) which is a clear, intumescent varnish to be finished with Thermoguard Fire Varnish Overcoat (Exterior) available in a clear or stained matt or satin finish (a gloss finish is available in batch quantities for large projects). The Thermoguard Fire Varnish Overcoat provides protection against UV, weathering and wear whilst Thermoguard Fire Varnish Basecoat provides the Fire Protection.

Intumescent Fire Protection

When exposed to fire, the Thermoguard Fire Varnish System expands to create an insulating barrier, protecting timber surfaces from flames, heat and oxygen and suppressing emission of deadly smoke & gasses.

Specification and Application

Prepare and apply – (INTERIOR)

  • 1 coat of Thermoguard Fire Varnish Basecoat
  • 1 coat of Thermoguard Fire Varnish Overcoat (Exterior) Matt or Satin


  • 1 coat of Thermoguard Fire Varnish Basecoat
  • 2 coats of Thermoguard Fire Varnish Overcoat (Exterior) Matt or Satin

Available Pack Sizes

Application by painters, decorators & other professional users only. Refer to instructions on Fire Varnish Base & Overcoat containers.

Previously Varnished and Stained Surfaces or Wood Preservers

The Thermoguard Fire Varnish System can be applied over firmly adhered standard clear varnish. For existing stained varnishes, stain coatings, old fire coatings or if in doubt, contact our Technical Department on 0113 2455450.

  • If preservatives are required, use rapid drying clear non waterrepellent grades*.
  • For tanalised or other preservative treatments, contact our Technical Department.

*Allow adequate time for stain or preservative fluids to escape before applying the Thermoguard Fire Varnish System.

Fire Test Standards and Certification

  • BS EN Class B s2 d0
  • Class 1 and Class 0

Note - For 30 or 60 mins Fire Resistance see Thermoguard Fire Varnish 30 & 60 Minute System.

For fire protection to doors, see Fire Door Upgrade Kits

Thermoguard will issue a Certificate of Supply upon request for each correctly specified project for Insurance, Fire and Building Control Authority and Client Records against proof of purchase.


  • Cover, countersink & fill, or use non-ferrous, galvanized, stainless or sheradised fittings
  • Ensure surfaces are dry, clean and free of all contamination.
  • Varnished, sealed or non-porous wood should be abraded thoroughly with medium grade silicone carbide abrasive when dry to provide a good key.

Application to OSB/Sterling Board

This is a board made of chips of wood glued together to form a hard non-decorative board. If it needs fire coating, Thermoguard Fire Varnish or Timbercoat System can be applied to it. However we first recommend a test is carried out by applying a small amount of the proposed coating to the board to check for "cessing" / "cissing" (where coating gathers together in lumps and may leaving bare patches between). If this occurs the board should be degreased/cleaned and allowed to dry before testing again - if this still does not provide a satisfactory application please contact our Technical Team for further advice on 0113 2455450 (option 2) or send a message to [email protected].


During application & drying of the full system:-

  • Ensure surfaces are thoroughly dry – max 18% moisture content.
  • Maximum relative humidity RH 75%.Ensure adequate ventilation.
  • Minimum air temperature 6°C. Minimum surface temperature 3°C above dewpoint – avoid condensation.

NEW Fire Regulations and Tests Explained

  • The new fire standard BS EN test lasts 20 mins. with airflow replaces the old BS 476 tests which lasted 10 mins and restricted airflow.
  • The new standard for flamespread and heat release Class B replaces Class 0.

The new BS EN tests also monitor -

  • Smoke & Gas “s” – s1 + s2 are none or very low & compliant levels, s3 moderate , s4 high smoke.
  • Flaming Droplets or Airborne particulates – d0 is none, d1 some, d2 + d3 moderate > high levels.

IMPORTANT FIRE PRODUCTS NOTICE: The information displayed on this website should be used as a guide ONLY and our Technical Department should be contacted to obtain a tailored specification and any advice necessary before you place an order for fire protection products. Fire protection products are non-returnable except in accordance with Condition 8 of the Terms and ConditionsWe will not be held liable for any resulting damage to property, human life or monetary costs incurred due to the incorrect specification you have prepared or use of fire protection products caused by your negligence, including your failure to have contacted us to obtain the relevant advice/specification.

It is your responsibility to read the Product Data Sheets (available below) before you place an order and prior to application of the product. The content of this website is our best recommendation and is not advice. Coverage rates quoted are approximate, you agree that coverage depends on the condition of the substrate, surface absorption, texture and application method. We ALWAYS recommend a trial area is coated to ensure the product meets your requirements before use.

Product Details

Data sheet

Brush, Roller, Spray
Supplied in pre-measured packs to apply 1 coat to 20m²
Dry for Topcoat (at +20°C)
Min. 8hrs but within 4 days - basecoat must be hard dry before applying overcoat

Customer agrees that before placing an Order, Customer has read and understood the most up to date Product Data Sheet for the Product. Where we have access to the Product Data Sheet from the manufacturer, we will either provide a copy on request, or include a link to the Product Data Sheet available on the manufacturer’s website. Customer further agrees that we have no liability for any errors or omissions contained within the Product Data Sheets. For more information, please see our Terms & Conditions of Sale.

questions Rob Small on 2019-10-28 23:39:52

1. Can Thermoguard Fire Varnish Basecoat be overcoated with a polyurethane varnish (Bona Mega) instead the of the Thermoguard topcoat? I would like to be able to match existing finishes. 2. Once the activator is added to the Thermoguard Fire Varnish Basecoat what is the product's working time before it goes off? Ideally I would like to be able to apply the basecoat to plywood sheets in batches.


Thermoguard Fire Varnish Basecoat MUST be overcoated with either Thermoguard Fire Varnish Overcoat Exterior or Interior grade and nothing else. I would suggest the best course of action would be to call our Technical Team on 0113 2455450 (option 2) to discuss your project and it's requirements as we should have a way for you to achieve what you require.

questions Douglas Murray on 2019-09-05 09:00:40

I need to apply Fire Retardant varnish, or similar, to external timber weatherboard (or shiplap) on which there are two coats of a water based timber colour preservative. I have to maintain the colour for a planning condition, but if needed could overcoat any fire retardant system if possible. It is a timber storage shed and only two sides need to be treated - approx 40 sq m in total. Thoughts on the proper application required, and the supply of certificates is necessary


Assuming BS Class 1/0 or EN Class B is the level of fire protection required (please check with your relevant authority and if different please advise) then we would recommend Envirograf ES/VFR Clear Class 1/0 & EN Class B System for Wood (Exterior).

questions james watt on 2018-10-15 11:46:23

Can this be put over painted wood ?


No, but if you contact our Technical Team on 0113 2455450 (option 2) or [email protected] with your full requirements we may be able to provide a solution for you.

questions Robert Harris on 2016-11-10 20:02:28
Question: Hi Does the clear varnish product turn a mdf veneered board from no fire Protection to 30min protection? Is there a choice of satin or gloss finish too? Is the varnish fully clear or is lightly tinted?

Thermoguard Fire Varnish Basecoat provides BS Class 1, Class 0, EN Class B s2 d0 protection to timber and timber derived substrates. It is a clear varnish (not lightly tinted) available in matt, satin or gloss finishes.

30min protection can be achieved using the Thermoguard Fire Varnish System but approval must first be sought from the governing authority on the project for information provided by our Technical Department. To receive a 30min specification and supporting documentation for submission, please contact our Technical Team on 0113 2455450 or [email protected]


Question about the product

* Required fields
You might also like

Thermoguard Fire Varnish Overcoat (Interior)

Thermoguard Fire Retardant Varnish Overcoat (Interior) is for use in combination with and over Thermoguard Fire Varnish Basecoat in external applications. ADVANTAGES For timber/timber derived substrates Clear, UV and wear-resistant finish Certificate of Supply available Certificated when used over the basecoat: BS EN Class B s2 d0...

Price £54.00
In stock

Thermoguard Fire Varnish 30 & 60 Minute System

Thermoguard Fire Varnish 30 and 60 Minute System is a clear intumescent varnish for interior and exterior timber surfaces. Each pack contains the correct amount of basecoat (Fire Varnish Basecoat) and topcoat (Fire Varnish Overcoat (Exterior)) to ensure protection is achieved inline with the manufacturers recommendations to the respective area...

Price £157.00
In stock