For some materials – timber weatherboards, for example – there are many methods that can be used to remove existing paint, from a hot air gun, chemical strippers, machine sanding, hand scraping and sanding, to more expensive systems that involve carbide blades set in a spinning drum or even infra-red heat.

There are some materials that paint cannot be easily removed from, including plasterboard and fibrous plaster, softboard, particleboard, thin timber veneers and fibre-cement or textured exterior coatings.

Apart from knowing the material that you are removing the paint from, it also helps to know in advance what type of paint you are removing – water-based or solvent-based – because not all techniques work well with each paint type.

To determine whether a paint finish is water-based or solvent-based:

  • Soak a cotton ball in rubbing alcohol (isopropyl or ethyl alcohol), an acetone-based nail polish remover or lacquer thinner
  • Rub it over a small, inconspicuous section of wall
  • If paint comes off, it is water-based; if unaffected, it is a solvent-based paint.

The use of white lead was banned in 1979, but red lead can still be found in a few special-purpose paints that often have a distinctive red colour. Care needs to be taken when removing old lead paint as part of preparations for new painting. When lead is taken into the body (swallowed or breathed in as dust) it can cause potentially serious illness.

Hot air guns

Hot air guns direct a stream of air that has passed over an electric element onto the paint surface, softening it so it can be scraped off. They are most often used to remove paint from timber surfaces, such as weatherboard claddings. The flow of hot air is moved along the surface, taking care not to burn the timber by spending too much time on one spot.

Polyurethane, varnish and shellac finishes will soften and become sticky with hot air gun application, but they may become even more difficult to remove than by cold scraping. Waxes, oils and stains soak into timber when applied and cannot be removed with a hot air gun.

Chemical stripping fluid is liberally brushed onto a surface, left while the paint softens, and then the paint is scraped off. The surface must then be washed down thoroughly to remove stripper residue. Protective clothing must be worn to prevent skin contact and to protect hands and eyes, and strippers should only be used in well-ventilated spaces. Chemical strippers can be messy to use, but are useful on intricate or profiled woodwork such as fretwork or timber mouldings. They should not be used beside aluminium or glass.

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Hand scraping

Hand scraping is a slow method not suitable for large areas. Scrapers are best used in conjunction with others tools such as hot air guns, or for paint that is already loose or flaking. Scrapers are available with different profiles suitable for mouldings and profiled timbers.

When using a scraper, take care not to gouge or chip the substrate, not to work against the direction of the timber grain, and where a scraper blade is replaceable, fit a new blade when the old one becomes blunted.

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Machine sanding and other mechanical methods

These methods include belt and orbital sanders, shavers that use carbide blades set in a spinning drum, and abrading fittings such as wire brushes used with an electric drill.

Some of the sanders and shavers include dust-catching bags or vacuum systems that reduce the amount of dust produced. Operators should wear earmuffs and dust masks.

Belt sanders are suited to heavier work, remove material faster and keep the sander flat on the surface to give an even finish and prevent gouging.

Orbital sanders are often more compact and lighter than belt sanders. They are best used for removing thin coatings or for final preparation after most of the paint has been removed by another method.

Attachments used in power drills should be used with care because of their tendency to score substrates such as timber.

Newer paint removal devices on the market include one that shaves old paintwork off with carbide blades. While these can give faster results, they are also considerably more expensive than the hot air guns or sanders aimed at the DIY market.

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Waterblasting

Waterblasting is best used for removing loose or flaking paint from hard external surfaces such as metal, concrete or brick. It does not normally remove paint that is still well adhered to the substrate. Waterblasting should not be used on timber weatherboards as the pressure can drive water through gaps between weatherboards and around widow sashes. It should not be used on plaster-based  textured finishes because it can damage the texture.

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Burning off with a naked flame

The use of naked flames to burn off old paintwork with LPG torches and the like has reduced as other tools have become available. While this is still an effective way of removing paint, it comes with the risk of setting fire to the building, injury to the operator, scorching of timber or cracking of window glass. Burning off with a naked flame is best left to someone with experience.

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Hand sanding

It can be a tedious and dirty job, but hand sanding is still an important part of the final preparation after other methods of paint removal have been used. Oil-based paints, because of their harder surface, respond well to sanding. Softer water-based paints tend to clog sandpaper.

Sandpaper has the grit size printed on the back – the large the number, the finer the grit. Use of coarser papers (with a number such as 60 or 80) is typically followed by use of finer papers (such as 180 or 220). Don’t use an extremely fine paper before painting – paint doesn’t adhere as well to surfaces that are absolutely smooth. Some papers have a letter to identify paper strength, with A being the lightest weight.

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Removing lead-based paint

Although lead has not been an ingredient in regular house paints in the last 30 years, with houses that are older than that, it is possible that the old layers of paint being removed may contain lead, so care should be taken.

Lead can be a health hazard if fumes, dust or paint fragments are swallowed or breathed in during paint removal. Precautions should be taken:

  • Wear an effective dust mask.
  • Use drop sheets, and remove dust and paint fragments. Put them in the rubbish in sealed bags.
  • Keep doors and windows closed to prevent dust entering the house.
  • If the equipment you are using has a dust catcher or vacuum device, use it.
  • Keep children and pets away when paint is being removed.
  • Remove pets’ food and drinking bowls and toys.
  • Wash hair and skin thoroughly after paint stripping, particularly before eating.

For more information see Health and safety: lead-based paint, and Guidelines for the Management of Lead-Based Paint

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Just before starting to paint

  • Lay drop sheets to protect surfaces under the work area
  • make sure you have enough paint for the job before starting
  • read the instructions thoroughly before opening the paint container
  • make sure the paint is stirred thoroughly with a broad flat stirrer
  • check that the surface to be painted is dry
  • Remove dust with a clean brush or clean lint-free cloth
  • check the weather forecast – do not start painting if rain or strong winds are forecast or if the temperature is below 10° or above 25°.

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