Painting Plastisol Cladding: A How To Guide

painting plastisol cladding

What Is Plastisol Cladding?

Over the last 35 years or so industrial buildings have been constructed with Plastisol Cladding sheets.

Painting Plastisol CladdingPlastisol Cladding is produced from a hot dipped zinc coated high tensile steel sheet. This is then shaped into the required profile then oven cured to ensure optimum adhesion. Application of a 25 micron thick high grade Polyester enamel paint gives the surface it’s colour range. Cladding sheet manufacturers include leading companies such as Corus, Arcelor and Dobel.

Metal cladding sheets offer excellent corrosion resistance and climatic protection together with abrasion resistance and high strength.

Before Plastisol Metal Cladding was introduced buildings were clad with a variety of materials. Older materials include copper, brass, bronze, stone, cedar, and other woods.

More recently asbestos became popular. Unfortunately, this was discovered to cause serious health issues. Diseases such as Asbestosis or Mesothelioma, a cancer of the inner lining of the chest wall or abdominal cavity are now rife. Blue and brown asbestos (the two most dangerous forms) have not been imported into the UK for nearly 20 years and their use was banned in 1985.

Painting plastisol cladding is regarded as the most cost effective option of protecting the metal sheeting as well as the best method of rejuvenating or changing the colour.

Painted Plastisol Cladding will last approximately 10-15 years longer than untreated or un-coated cladding. Warranties are available for up to 20 years for larger projects.

You can easily repaint Plastisol metal cladding cost effectively by spray. This makes the cladding easy to ‘re-brand’.

Signs Of Aged Plastisol Cladding Include:

  • Discolouration – caused by harsh weather, exposure to UV light, moisture in the air especially in costal areas where the air often contains salt.
  • Chalking – where paint naturally and literally wears away, different types of paint degrade at different rates.
  • Separation of layers, delamination – unsightly damage caused by moisture seeping in and creating rust, which can split the top polyester layer from the metal of the cladding.
  • Rust holes appearing close to the edges of the plastisol sheets.

Rusting Plastisol Cladding Paint

How to Prepare Plastisol Cladding For Painting

The most important consideration as with all painting projects is preparation.

Centrecoat GS36Firstly, when coating a roof remove any debris and moss by sweeping the entire roof with a broom. Next, apply a fungicidal wash such as Centrecoat GS36 or Rustoleum AMW Wash. This will kill and spores and green growth on the cladding. This is essential as if they are not removed following painting the spores will start to grow and push through the new coating.

The third step is to degrease the Plastisol cladding with a water-soluble degreaser such as Rustoleum ND14.  The ND14 cleaner is added to a jet wash as a 5% solution, clean the entire area to be painted should be thoroughly washed and degreased using high pressure washing at a pressure of 3000-3500 psi. (approximately 200-250 bar).

Do not allow this cleaning solution to dry on the surface. Ensure to remove the cleaning solution and all resulting loosened contamination via rinsing with copious amounts of clean fresh water.

Repairing Plastisol Cladding

Carry out any repairs to holes or cracks. Remove any areas showing signs of rust to standard ST3. This means no brown rust should be visible.

Monti MBX Metal BlasterWe would recommend a Monti MBX Metal Blaster to carry out this work. Feather back where a “leading edge” of the existing coating is present. This is more important on vertical cladding as when the sun shines on the cladding at an angle poor preparation becomes more evident.

Any gaps between the sheets should be filled with an elastomeric sealer such as Rustoleum Elastofill.

You can find Plastisol Cladding on vertical surfaces as well as low pitched roofs. Plastisol has to withstand all weather conditions. In coastal environments the cladding can be subject to salt in the air. This will reduce the life of the metal cladding significantly.  Painting is the most cost effective option of protecting the metal sheeting. It is also the best method of rejuvenating or changing the colour.

What Is The Best Method Of Painting Metal Cladding?

The best method of applying the paint is by spray application. There are different types of sprayers such as airless, air assisted spray or HVLP. As cladding is normally a large area we do not recommend to hand or roller paint. It often looks blotchy and has different sheen levels. It can also take a lot longer than you think to paint such a large area!

Slow drying paints are also susceptible to dust sticking to the wet surface leaving an unsightly finish. Many solvent based paints are not flexible enough to cope with the movement of the plastisol sheets and will soon peel or flake.

Which Paint Should I Use on Plastisol Cladding?

Zinc primer or a zinc rich primer is advised to be applied to correctly prepared steel, this is normally achieved by the use of an angle grinder or a Monti electric wire brush.

You should prime any areas of bare steel, galvanised steel, zinc and aluminium on the same day. This stops the surface from oxidising or gingering. Following preparation in warmer conditions prime with 1-2 coats as required of Rust-Oleum Mathys Metal Cladding Primer at an approximate theoretical coverage rate of 12.5m² per litre/per coat. Allow to dry for a minimum period of 1 hour at 20°C between coats before applying a further coat.

Painting Plastisol Cladding

If you do not have rust, Rustoleum Metal Cladding Primer can be applied, this is advised when you intend to change the colour. Rust-Oleum Mathys Metal Cladding Primer can be applied to the whole surface of vertical cladding and this will not only help opacity but will increase adhesion. It will also help prevent future corrosion and extend the life of the paint.

When Can I Paint Plastisol Cladding?

The choice of paint can depend upon a range of factors. The ambient temperature is the most important consideration. If it is cold we recommend the use of cladding paint that uses xylene as it’s solvent. For Spring and Autumn, we recommend a paint that is based on white spirit. For Summer, we recommend a water based cladding paint.

A paint that we would recommend for use in winter months is the Pronto ProTect Vinyl Sheen Primer / Finish. This is a single pack flexible coating with high levels of impact resistance. It provides outstanding adhesion to both clean steel, galvanised surfaces and existing prepared finishes such as metal cladding. This paint also benefits from being available in over 3,000 colours as well as metallic shades.

Flexible cladding paintFor warmer conditions such as Spring and Autumn our recommendation would be the Centrecoat HB Anti-Corrosive Cladding Paint. This coating is low VOC below 500g/l – Department of Environment PG6/23(04) table 6 – Emissions Compliant Coating.

A high build, low odour, flexible one coat primer / finish cladding paint formulated to protect profiled metal cladding and plastisol from the elements. Tintable to a wide range of RAL and BS shades, this semi matt high build coating is an ideal solution to protect metal and Plastisol cladding as well as old painted surfaces.

For warmer conditions, ie late spring through normally to mid September, we would normally suggest Rustoleum Noxyde. However it is only available in a small range of colours. If you require a much larger range of colours consider Rustoleum Metal Cladding Topcoat.

Painting Plastisol Cladding In Harsh Environments

Cladding paints offer good adhesion to aged Plastisol. They are also flexible (some up to 400%) and relatively colour stable. This makes then ideal for re-coating of metal clad industrial, warehouse and out-of-town retail units subject to normal C3-C4 UV/atmospheric conditions.

For coastal areas we would recommend a C5M product such as Rustoleum Noxyde. Noxyde is a water based paint that offers unrivalled protection of metal cladding and for larger projects. Promain can offer up to 15 years warrant on the paint system.

For a more decorative finish we recommend Rustoleum’s Metal Cladding Topcoat. This product is available in over 30,000 different colours.You can also apply it in just one coat.

Can I Paint New Plastisol Cladding?

During production Plastisol contains oils. These oils will stop the absorbtion of the paint into the surface. This will stop the paint from correctly adhering to the surface. Paint may delaminate in the form of flakes or blisters. This may not happen for a year or maybe longer.

New plastisol cladding

Many people who experience this often blame the paint rather than the surface. We advise that new Plastisol is left to weather or oxidise. We would normally recommend that this takes about a year to happen.

During this time rain and UV rays from the sun will wash out and dry the oils. Afterwards the surface will be suitable for the application of paint.

Are There Different Types Of Metal Cladding Sheets?

The most common type of metal cladding is the box cladding that has a leather finish. There are other metal cladding types such as PVDF, PVF2, Polyester, Polyurethane, Power Coating, etc. These Box Cladding finishes require special consideration and in most instances will require a special primer such as Rust-Oleum PVDF Primer or abrading to create a profile. Treat new galvanised corrugated metal sheeting with Mordant Solution prior to painting.

What Should I Consider When Choosing Cladding Paint?

As above, the time of year you intend to paint can effect matters. Also, the method of application should be considered – Is the product formulated for spray or brush application?

Rustoleum offer a family of products called Noxyde. Noxyde is suitable for application by airless sprayer where as the Peganox has been developed for brush application. For winter application Rustoleum offer Pegarust a solvent based coating rather than water based.

Also consider if you intend to apply the paint by spray. Over spray can cause damage to the surroundings as the paint may not be dry when it lands. Noxyde benefits from “Dry Fall Certification”. This means that the paint will be dry after about 1-2 metres of travel from the spray gun. This reduces the likelihood that the paint will be wet if it hits other assets.

Can I Get A Warranty On Cladding Paint?

For larger projects over 500m2 Rustoleum are able to offer a free manufacturers 10 or 15 year warranty when Noxyde is applied at the correct film thickness. If you are considering a warranty then please contact Promain. This must be done at least 4 weeks before the job commences. This is so that we can organise a site visit to assess the condition of the roof. The site visit also enables us to produce the neccessary paperwork for the warranty.

Do I Need To Paint All Of The Cladding Sheets?

If the cladding is only corroded along the edges, (know as Cut Edge Corrosion), there is a system recommended for repairing this (see Noxyde Cut Edge Guide). Prepare any affected areas by mechanical abrasion. For best results  we recommend sand blasting.

Preparing To Paint Plastisol Cladding

Then stripe coating with an anti-corrosive primer and allowed to dry. Followed by a jointing compound such as Rustoleum Elastofill, this used to seal the Plastisol sheets preventing further water ingress.

Alternatively, for larger gaps a roofing reinforcing bandage similar to the Rustoleum Noxyde Tape For Edge Laps can be applied. Finally, you can apply the topcoat. Always refer to the manufacturers data sheets for correct consumption.

How Long Does Cladding Last?

The Metal Cladding And Roofing Manufacturers Association Limited estimate that Plastisol sheeting has a design life of between 10 and 23 years to first maintenance. Lighter colours tend to last longer than dark colours hence the variation life expectancy.

There are many factors that can affect the paints life:

  • Location – coastal locations with have more salt attack, exposed areas will suffer from rain or sunlight, shaded areas often do not dry out in the winter and moss can grow on the surface causing further damage.
  • The pitch of the roof  – This determines how fast water runs off the surface. It seems obvious but steeper roofs dry much quicker that flat roofs.

The guidance in this article is in good faith but without warranty. We have only covered a small range of scenarios and have not focused on any one manufacturers system.

If you would like further information on painting metal cladding please contact our Technical Department. It is best to contact us for details  before commencing any works. This ensures you follow the correct specification. Remember specifications will alter for a wide range of reasons such as varying circumstances, environments, substrates, etc.

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