ACS S42 Intumescent for Timber

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  • ACS S42 Intumescent for Timber

Intumescent paint for timber

We provide a full specification service and certification for building control please call for technical advice and product costings on 01935 414012. Txt 07421 747462 or email us

A single-pack, waterborne intumescent coating for application to timber and timber related products. Available in clear or white.

When used correctly the product imparts fire resistance to BS476 Parts 6 and 7 against surface spread of flame, and to BS476 Parts 20 and 22 for 30 and 60 minutes insulation (depending on substrate).


To protect timber and timber related products such as hardwoods, softwoods, cladding, boarding, MDF and certain plastics. Suitable for protection up to 60 minutes when used on certain dimensions of timber and with the correctly specified primer/topcoat system. Extensively tested at a number of NAMAS approved laboratories to satisfy the requirements of BS476 Parts 6,7,20 and 22. Normally specified for use with the S42/04 Topcoat or S42/AEC Acrylic Emulsion. Tested to BS EN13823: 2002 (SBI) and BS EN 11925-2: 2002 Ignitability achieving a classification of A1- B/s1/d0 on both particleboard and MDF. Also tested to EN 1364 – 1: 1999 on 20mm Norway Spruce shiplap cladding, achieving 66-minutes resistance.


A blend of copolymer resins in water with fire retardant additives and pigments.


Colour: White

Drying Times @ 20°C

Touch: 1-2 Hours

Hard: 2-3 Hours

Overcoat: 3-4 Hours

Shelf Life: Approximately 18 months in un-opened containers

Thinners/Clean-up: Water

Theoretical Coverage: Variable depending on the level of protection and

dimensions of substrate

Specific Gravity: 1.2 – 1.35g/ml

Storage: Protect from frost, store above 5°C in dry



Ensure all surfaces are clean, dry and free of oil, grease, nibs, splinters and any loose or flaking material.

Make good any cracks or defects and missing knots with timber plugs or CS Stopper (not Brummer). Glossy surfaces of prepared timber or over-planed finishes should be lightly abraded with a fine grit aluminium oxide paper or 000 wire wool to create a key. Remove dust by vacuum sweeping.


All existing coatings should be in sound condition and well adhered to the substrate. If necessary, assess the condition in accordance with BS3900 Pt6 (cross hatch test). Loose or flaking paint should be thoroughly removed and scraped back to a sound line. New solvent-borne stains should be left for a minimum of 14 days after application and then washed down with a mild detergent solution followed by a clean water rinse and a period of drying. Waterborne stains should be left for a minimum period of 7 days prior to washing as above.

All painted or stained surfaces will require a priming coat of S42/AP Adhesion Primer.

All exterior applications should be protected from weather and cold during application and drying.


Stir the contents thoroughly prior to and periodically during application. Apply by brush, medium knap roller or spray. If necessary thin with up to 10% warm water, but be aware that application rates will have to be reduced to take into account the lowering of the active ingredient content (i.e. if thinning with 10% water, reduce application by 10%, therefore an application rate of 8m2/litre will become 7.2m2/litre). Do not exceed the coverage rate quoted on any specification provided. Always work to a wet edge, lay-off early and do not attempt to brush out once the product has started to dry.


Do not apply at rates other than those specified. Protect from frost and weather during application and drying. S42/01/E is unaffected by atmospheric or substrate moisture but do not apply if the substrate temperature is below 10°C or if the relative humidity rises above 75%.

We advise that you seek approval from your Building Control officer before commencing any work involving the use of intumescent coatings.


1.0lt, 2.5lt and 5.0lt full aperture paintainers. Other pack sizes available subject to minimum order and manual handling restrictions.

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