Key Questions - Fire Retardant Treatments

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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.

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What industry standards do Lonza fire retardant treatments meet?

The fire performance for all materials that are to be used in buildings, including wood and wood based panel products, are stated in Document B of the UK Building Regulations.
Requirements are expressed as a classification:
The performance normally required for wall and ceiling linings is Class 1 Surface Spread of Flame in accordance with BS476:Part 7 or Euroclass C in accordance with BS EN 13501-1: 2002.
The performance normally required in higher risk areas such as escape routes and staircases is Class 0 BS 476: Parts 6 & 7 or Euroclass B in accordance with BS EN 13501-1: 2002.

Adoption of the Construction Products Directive into UK legislation requires all products to meet the six Essential Requirements of that Directive. This is proved by demonstrating compliance with European Product Standards when they become available and marking product with the CE mark as a declaration of compliance.

Technical files are available for a wide range of panel products treated with DRICON. Lonza Wood Protection has invested in having these files available for its customers. It is the responsibility of the company supplying the panel product to have its notified body in place and request access to Lonza Wood Protection data files. It is recommended that you discuss your requirements directly with Lonza Wood Protection.

Every aspect of DRICON processing, including raw materials, product manufacture, management systems, treatment, drying, performance and properties is the subject of a British Board of Agrément (BBA) assessment under certificate number 87/1741. DRICON is the only fire retardant treatment for timber to achieve this prestigious BBA accreditation. To view the BBA Cretificate click here.

NON-COM Exterior treated cedar shingles, shakes and Yorkshire Boarding, also meet the criteria of BS 476: Part 3 AA/P60 Roof Penetration Test.

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What timbers can be DRICON treated?

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

Please contact Lonza Wood Protection for advice on treating to meet specific standards or if the materials you intend to use is not shown 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

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What materials can be NON-COM Exterior treated?

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

Please contact Lonza Wood Protection for advice on treating to meet specific standards or if the materials you intend to use is not shown 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®

WBP PLYWOODS
Far Eastern, Far Eastern Marine, Gaboon or Okoume, Spruce, Douglas Fir
Birch throughout, Birch Combi

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

*Complies with BS476: Part 3 AA/P60 Roof Penetration Test.
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What are Class 1 and Class 0?

These are classifications of fire protection for timber within BS 476 Part 6& 7 and measure of the lateral spread of flame along the surface of a timber component. Class 1 conforms to BS 476 Part 7 and is the performance normally required for wall and ceiling linings. Class 0 is a more stringent requirement to BS 476 Parts 6 & 7 and is normally required in higher risk areas of a building, such as escape routes and staircases.

To achieve Class 1 BS 476 Part 7 classification, the spread of flame must not be more than 165mm in 10 minutes.

Class 0 BS 476 Parts 6 & 7 classification embodies the requirements of the surface spread of flame (Part 7) as above but also Part 6 which is known as the 'fire propagation index', a measure of the heat released when timber burns. Timber achieving a Class 0 specification must achieve a fire propagation index of I ≤ 12 & a sub-index I 1≤ 6.

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What are Euroclasses?

Under the Construction Products Directive there is a move towards 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.

In England and Wales, the fire requirements for buildings are dealt with by Approved Document Part B to the Building Regulations - Class 0 and Class 1.

Euroclass B transposes to Class 0 and Euroclass C transposes to Class 1.

PLEASE NOTE: It is not possible to obtain a national class and sell to a European Class or vice versa. In other words you must carry out testing against European Standards to achieve a European Classification.

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What fire performance is required for external timber cladding?

The fire performance of timber cladding for a building is commonly stipulated by Building Control - this is usually either Class 1 BS 476 part 7 or Class 0 BS 476 Parts 6 & 7, with Class 0 being the higher level of fire protection. 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 Class 0 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 Lonza Wood 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.

If you require advice regarding the fire treatment most suitable to your specification/ timber type please contact Lonza Wood Protection - 01977 714000.

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How do Scottish Buildings Regulations correlate to Class 1 & Class 0?

The 'High Risk' category in the Scottish Buildings Regs is equivalent to Class 0 and the 'Medium Risk' category is equivalent to Class 1.

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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 Lonza have been used on many fire retardant projects to give a superior, long lasting decorative finish. For more details on RESTOL visit http://www.archchemicals.com/Fed/WOOD/Products/DecorativeProducts/restol.htm

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.

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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 Class 1 and air dried following treatment. Each end of the board is usually sprayed, providing a colour code reference to indicate DRICON protection.

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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.

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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.

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Can you fire treat OSB board or MDF?

No - because of the make up of these products they will tend to 'blow' or expand within the pressure treatment.

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I want to fire treat a staircase. Which treatment should I be looking at?

DRICON is the most suitable treatment for staircases components, achieving a Class 0 protection. DRICON treated staircases have been assessed in the TF2000 fire test on a single timber staircase in a six storey building. The detail of this is available from Chiltern International Fire - www.chiltern.co.uk

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What will be the weight increase to fire retardant treated timbers/plywoods?

Typically fire retardant treatments adds around 12-15% to the weight of plywoods and solid timbers.

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What fire retardant treatments are suitable for use on the London Underground system?

DRICON is the only approved treatment for use on the London Underground system. Material needs to conform with Metronet/London Underground Standard 2-01001-002 Fire safety Performance of Materials Ref DPM-0735 July 2007. Treated material should be colour coded/hot branded to conform.

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Will NON-COM Exterior treatment darken the colour of Western Red Cedar?

Untreated western Red Cedar will darken slightly when first exposed to UV light. NON-COM Exterior treatment of Western Red Cedar may result in a slight darkening of the timber comparable to this natural process. In time the treated timbers should weather to the same as untreated timber.

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How does gluing affect treatment/treated timbers?

In general glued assemblies can be safely treated with either DRICON or NON-COM Exterior provide suitable waterproof glues have been used. We do recommend that advice is sought from Lonza before sending material for treatment.

When DRICON treated material is to be glued, again arch should be consulted. Phenol formaldehyde, melamine formaldehyde or resorcinol types are generally recommended depending upon the end use.

For NON-COM Exterior treated timbers, advice from Lonza should always be sought if the timber is to be glued after treatment.

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Is there a model specification for Lonza fire retardant treatments?

Model specifications for Arch fire retardant treatments, including preparation of the timber for treatment, are readily available in Word format from the Lonza web site.
DRICON - http://www.archchemicals.com/Fed/WOOD/Products/FireRetardantProtection/dricon.htm
NONCOM EXTERIOR - http://www.archchemicals.com/Fed/WOOD/Products/FireRetardantProtection/noncom.htm

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If the fire treated timbers are cut on-site do they need any extra protection?

Any surfaces of large section timbers exposed by unavoidable cross cutting should be liberally brushed with ENSELE end grain preservative solution. ENSELE is available directly from Lonza Wood Protection.

Any rip sawn material should not be installed in service and should be returned for re-treatment.

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Can I fire treat timbers to be used within indoor Swimming Pools facilities?

DRICON is the recommended treatment for timbers used in ceilings and claddings within the typically humid conditions of an indoor swimming pool facility. A decorative coating may be applied on the treated timbers but we would recommend leaving the timbers 'natural' as subsequent maintenance may prove difficult.


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How should waste treated timbers be disposed of?

Small off-cuts can be disposed of as industrial waste. Larger quantities of waste and redundant timber should be disposed of by a competent Waste Disposal Contractor.

Waste timbers should not be used for animal litter or bedding or fuel for barbeques or stoves.

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