Fire Retardant Q&A - Arch Timber Protection

What is the difference between DRICON and NON-COM Exterior fire retardant treatments?

DRICON is a waterbased, Humidity Resistant (HR) type formulation that is applied under controlled conditions in a vacuum pressure impregnation plant, followed by kiln drying to return the timber to an acceptable or specified moisture content. The DRICON treated timber/sheet materials are suitable for all interior applications and also for weather protected external use - materials must be protected from direct wetting by the application of an applied and properly maintained stain or paint finish. Typical end uses for DRICON treated material would be internal building timbers, linings material, staircases, scaffold boards, swimming pool environments, lifeboat stations, rail and transport industries.

NON-COM Exterior is a polymer based, Leach Resistant (LR) type formulation. It is applied to the timber/sheet material by the same process as DRICON - pressure impregnation process and kiln drying - but the treated material is then also subject to a high temperature curing process to return it to an acceptable or specified moisture content. The NON-COM Exterior treated timber/sheet materials are suitable for full exterior and severe damp applications, without the need of a protective coating, although material can be decorated, if desired. Typical end uses for NON-COM Exterior treated material would be exterior cladding, exposed timber structures, cedar shingles and shakes and Yorkshire boarding material.

How do fire retardant treatments for timber work?

When subjected to fire the chemicals in both DRICON and NON-COM Exterior treated materials react with the combustible gases and tars normally generated by untreated wood, converting them to carbon char, carbon dioxide and water vapour. The insulating layer of char formed on the timber retards the process of combustion, reducing ignition, the rate of surface spread of flame and the amount of heat released, all providing additional time for the safe escape from the burning structure.

What timbers can be DRICON treated?

A wide range of timber and sheet materials can be treated with DRICON - see below.

SOLID TIMBERS
European Whitewood, European Redwood, Hem-Fir, Hemlock, Douglas Fir Western Red Cedar, Tulipwood, Siberian Larch, Willow, Sycamore, Maple, Oak, Ash, Sapele, Mahogany, Accoya®.

WBP PLYWOODS
Far Eastern, Far Eastern Marine, Gaboon or Okoume, Spruce, Douglas Fir Birch throughout, Birch Combi, Flexiply®, Bendiply.

Please contact Arch Timber Protection for advice on treating to meet specific standards or if the materials you intend to use is not shown below.

What materials can be NON-COM Exterior treated?

A wide range of timbers can be treated with NON-COM Exterior - see below.

SOLID TIMBERS
European Whitewood, European Redwood, Hem-Fir, Hemlock, Douglas Fir, Western Red Cedar, Western Red Cedar Shingles and Shakes, Siberian Larch, Thermowood®, Plato®wood, Iroko, Red Louro, Oak, Oak Shingles and Shakes*, Accoya® .

SPECIFIC COMMODITIES
Cedar Shingles, Oak Shingles, Whitewood , Yorkshire Boarding.

Please contact Arch Timber Protection for advice on treating to meet specific standards or if the materials you intend to use is not shown below.
 

What are Euroclasses?

Under the Construction Products Directive there has been a move away from the traditional Class 0 & Class 1 under BS476 Parts 6 & 7, towards a European harmonisation of standards for fire retardant treatment of timber - Euroclasses B & C.

To meet Euroclass B or C Specifications, timber/plywood is tested to EN ISO 11925 (Ignitability Test) & BS EN 13823:2002 (SBI or Single Burning Item Test).

The SBI test records parameters relating to the rate of fire growth, lateral flame spread and total heat release.

Euroclass Classifications are in accordance with BS EN 13501-1 (Fire classification of construction products and building elements)

The thresholds for compliance in relation to the above SBI criteria are higher for Euroclass B than for Euroclass C. Therefore, by definition, if timber/plywood conforms to Euroclass B then it also conforms to Euroclass C.
 

What fire performance is required for external timber cladding?

The fire performance of timber cladding for a building is commonly stipulated by Building Control and the main criteria when determining the fire performance required is the proximity of the building in relation to those around it.

If an elevation or elevations of a building are within 1 metre of a boundary, then a Euroclass B specification is usually required. Commonly, the timber battens and horizontal fire stops should also be treated as well as the timber cladding.

Occasionally Building Control will stipulate a 30 minute or 1 hour Fire Resistance. This relates to the fire performance of the STRUCTURE as a whole, not just the cladding. If this is the case, we recommend you seek advice from Arch Timber Protection in relation to the project in question.

Please note that the type of fire retardant treatment recommended, i.e. NON-COM Exterior or DRICON, depends on the type of timber cladding to be used and, very importantly, whether a coating is to be applied. Timber cladding treated with DRICON can only be used externally when a coating is applied to the timber and this coating must be maintained throughout the life time of the timber.
 

Can you recommend a decorative coating for use with Arch fire retardant treated timbers?

Firstly, a decorative coating is only required for DRICON treated timbers that are to be used in an external situation. NON-COM Exterior treated timbers do not normally require a decorative coating, but can be coated with an approved finish/coating, if desired.

However, if a decorative coating is preferred, it should be established that the coating will not downgrade the fire performance of the treated timbers, For instance, highly flammable finishes such as nitro-cellulose based lacquers must not be used.

The RESTOL range of high performance translucent finishes for wood from Arch have been used on many fire retardant projects to give a superior, long lasting decorative finish. For more details on RESTOL visit www.restol.info

Whichever decorative finish is to be used, the manufacturers own recommendations, as well as the recommendations on sound painting practices detailed in BS6150 - Code of Practice for the Painting of Buildings - should be followed.
 

Can scaffold boards be given a fire retardant treatment?

DRICON treatment is approved by the National Access & Scaffolding Confederation for scaffold boards. Treatment is normally to Euroclass C and air dried following treatment. Each end of the board is usually sprayed, providing a colour code reference to indicate DRICON protection.

Can you fire treat windows and doors?

Both windows and doors have a tendency to twist and distort within the fire treatment process and therefore we do not recommend treatment.

What types of metal fixings and fastenings are best to use with fire treated timbers?

Both DRICON and NON-COM Exterior treated timbers have been extensively tested with a wide range of metal fixings and fastenings and proofed to be no more corrosive than untreated timber. We would always recommend the use of high quality fixings and a check with the manufacturer of the fixings as to their suitability.