Intumescent paint coating frequently-asked questions for builders

all your questions answered

Below are a number of questions and answers about intumescent coating that are relevant to builders. Simply click on the question to see the answer.

what intumescent product should I be using?

Various intumescent coating products are designed to excel in different circumstances, so selecting the right one for your project requirements is essential.

This is a highly specialised field though and an accredited intumescent coating system contractor should be consulted.

how is an intumescent paint coating system applied?

Intumescent systems are applied using airless spray equipment.

Small areas, however, can usually be patched up if an architectural-level finish is not required..

can intumescent paint coatings be applied with a roller or brush?

Generally, no.

Intumescent coatings are very thick (72% volume solids or higher) and are usually applied using airless spray equipment to achieve an acceptable level of finish.

This also allows for accurate measurement of applied film thicknesses. Small areas that are not required to have an architectural-level finish may be touched up by brush.

can intumescent paint coatings be applied off site?

Water-based intumescent coatings are formulated for application on-site as they are more susceptible to damage from transport/handling.

Also, off-site coating facilities would be tied up for a considerable amount of time as the water-based intumescent coatings, depending on the film thickness required, may need to be sprayed in multiple applications over a number of days. They would need extended drying in good weather conditions to cure correctly.

Most solvent-based intumescent coatings can only be applied off site due to their high VOC levels.

There are some hybrid intumescent coatings formulated for both off-site and on-site application. They offer ‘fast track’ rapid curing, high-build, single-coat application, low VOC, primer-less system. Nullifire SC902 is one such system.

how many application coats does an intumescent paint coating system require?

A water-based intumescent system is applied in 600 micron coating thicknesses until the desired dry film thickness is reached.

Some hybrid intumescent systems can be applied in one coat up to 6mm if required. Contact the manufacturer for further details.

does an intumescent paint coating system require a primer?

Water-based intumescent paint coating systems require a primer.

A hybrid intumescent coating system like the Nullifire SC902 system is self-priming and does not need a primer in order to adhere to the steel substrate for internal applications. For external steel a primer should be applied for durability.

Can any primer be applied before an intumescent paint coating?

No, only approved primers may be applied prior to an intumescent coating.

Check the manufacturer's approved primers list for compatibility or, alternatively, contact the manufacturer.

can the intumescent paint coating be applied to galvanised steel?

Depending on the product, an intumescent system an intumescent coating system can be applied to galvanised steel but the steel substrate requires a light whip blast over the galvanisation before the intumescent is applied. It will need to be sand blasted according to SA1 (internal environment) or SA2.5 (external environment) as per AS1627.4 Metal finishing – Preparation and pretreatment of surfaces – Abrasive blast cleaning of steel.

Contact the product manufacturer for specific details.

can any top coat be applied over intumescent paint coatings?

Only approved top coats can be applied over intumescent coatings.

Contact the coating manufacturer - or visit their website - for a list of approved top coats for the coating in use.

can we achieve a 120/120/120 FRL for structural steel?

The three numbers represent the FRL for the structural adequacy (load), integrity (flames, gas, smokes) and insulation (temperature).

Generally intumescent paint for structural steel can only achieve the fire protection for the first figure - structural adequacy.

An intumescent-coated structural steel member could not prevent the movement of smoke and heat from one area to another.

Therefore intumescent coatings can only achieve a 120/-/- FRL (or 90/-/- or 60/-/-) for structural steel.

what is "steel section factor"?

Steel section factor, also known as Hp/A or ksm, is the ratio of perimeter to cross sectional area of structural steel members.

Hp/A gives an indication of the heating rate and dictates selection of the steel sections that can achieve the required FRL.

Generally, a larger, thicker steel member will have a lower Hp/A and lower heating rate than a smaller, thinner steel member.

This is important to consider because structural steel members with high HP/A will require more passive fire protection than those with low a Hp/A.

See more about steel section factor here.

what is the benefit of core-filling with respect to fire protection?

Core-filling reduces the required thickness of intumescent coating by reducing the effective section factor Hp/A which, therefore, reduces the cost of the fire protection coating.

when should we consider core-filling?

Core-filling is commonly used for structural steel columns to increase the mass for hollow sections.

The injected concrete helps with the fire resistance for steel.

It is essential that consideration is given to ensuring that core-filling meets with the required fire resistant level (FRL) when the thickness of the section is too thin.

See more about core filling here.

how much does an intumescent paint coating system cost per square metre?

The thickness of an intumescent coating is calculated based on the FRL, steel geometry and weight as well as what type of load it is supporting.

It is therefore impossible to provide a square metre rate as it is different for every member.

how can i get a price for intumescent fire protection?

There are approved applicators and distributers of intumescent coating systems Australia-wide who would be happy to assist with a quote.

One of the leading companies specialising in this area is Swart and Sons. Click the link below to visit their website.

visit the swart and sons website

who provides the certification for the fire protection?

The approved applicator/contractor should provide a certificate of compliance for the intumescent coating system and its application. This certification varies from state to state - check with your local regulatory authority for futher details.

is there a warranty for the intumescent paint coating product?

The manufacturer should be able to provide a warranty for their product. A warranty should be requested prior to the start of any project.

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