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From Habitat magazine - issue 09

The simplest way to transform the look of your house is with a coat of paint. Here’s how you can do it yourself.

Resene products

A coat of paint on the outside walls of your timber home can make all the difference in the world. But you must do it right for lasting benefit. The colour you choose is important; so is the type of paint you use, because your outside walls, windows and doors are exposed to all kinds of weather conditions for years.

Timber surfaces

Timber is a dimensionally unstable material which expands and contracts with changing moisture content. The timber surface is eroded by ultraviolet light, normally changing to a grey colour, leaving cellulose fibres exposed on the surface. Timber also provides a source of nutrient for mould growth and some timbers contain resins and oils which can affect the performance of paint.

Reconstituted timber products are subject, to a greater or lesser degree, to the same degradation as timber. Many of these products contain wax to improve water-resistance and wet-strength, which can upset the gloss and finish of the paint system and seriously retard the drying of oil-based paints.

Naturally occurring antioxidants in Totara and Matai timber inhibit the curing of alkyd enamels, primers, undercoats and oil-based stains. These materials can transfer through any solventborne system to affect subsequent coats. Highly filled undercoats can give an impression of having dried without really curing.

Freshly prepared Cedar has unique grain patterns and colour variations which can change rapidly and drastically under outdoor exterior exposures.

Surface preparation

Remove all moss and mould: Thoroughly clean down to remove all loosely adhered material. Treat areas of moss or mould infestation with Resene Moss & Mould Killer, correctly diluted with clean water. Leave for up to 48 hours to achieve full kill. For heavy infestations further applications may be needed. Wash thoroughly with clean water to remove all residue.

Wash surfaces: Use Resene Timber and Deck Wash to wash the surface and remove dirt and other contaminants.

Sand timber surfaces: Always sand along the grain to remove minor imperfections and any loose surface fibres. Loose fibres can be assumed to be present if the timber is left exposed to the weather for more than one week. Remove dust.

Sharp edges on timber are very difficult to apply paint to, as paint tends to flow away from edges, leaving weak spots. For best results these sharp edges must be sanded to a rounded profile.

All sanding dusts can be harmful and appropriate protection should be worn. In particular dust from old lead or chromate based paint can be harmful if inhaled or ingested. Seek expert advice if the presence of these materials is suspected.

End grains: Always coat end grains (i.e. underneath the doors) as this prevents moisture penetration into the timber surface which will eventually crack the paint film.

Moisture: Generally timber should not be coated when its moisture content is above 17%.

First coat

If the surface you propose to paint is already painted and in good condition, then you can go straight to topcoating.

In most cases Resene Quick Dry is the recommended primer for maximum flexibility and durability. Resene Quick Dry must be used as the first coat on Totara and Matai to seal the naturally occuring antioxidants.

Ensure all nail holes, damaged or split timbers are filled with a suitable filler and applied in accordance with the manufacturer’s instructions. Spot prime filler when dry with Resene Quick Dry.

NB: If staining is evident after the application of Resene Quick Dry, apply a further coat of Resene Enamel Undercoat.


Waterborne paints are the most suitable for exterior applications as they are more durable and flexible than solventborne paints.

Apply either Resene Hi-Glo (gloss), Resene Sonyx 101 (semi-gloss) or Resene Lumbersider (satin) at approximately 12 square metres per litre. Select the finish as outlined above depending on the desired gloss level finish. Follow label instructions at all times.

These products are all available in standard or Resene Cool Colour variants. Resene Cool Colours are designed to reflect more of the sun’s energy than a standard colour, reducing heat buildup in the coating and substrate and reducing heat transference inside.

Stained finishes

Film forming stains will eventually fail by flaking. Resene recommends non film forming, penetrating stains (such as Resene Waterborne Woodsman) and, even so, excess material must be wiped from the surface. Semi-transparent stains are not as durable as fully pigmented systems and Resene Waterborne Woodsman will require maintenance after two summers.

Apply two coats of Resene Waterborne Woodsman, wipe away any excess material sitting on the timber and allow to dry. For dressed timber, a third coat will be required after three months. Follow label instructions at all times.

Once you have finished the painting or staining return any unwanted paint or paint packaging to the Resene PaintWise service.

Weatherboard profiles

Type A is extremely difficult to coat with any paint system. The profile has two sharp edges and the scalloped face becomes almost horizontal at the bottom of the scallop. This means that on northern facing walls, parts of this scalloped face will always be at right angles to the sun and therefore subject to maximum ultraviolet light. The sharp edges, however, are the major concern. This is because paint pulls away from the sharp edge. In paint systems this results in a paint coating on these edges of only 50% of the film build achieved elsewhere.

Weatherboard profiles

Type B weatherboard does not have such a sharp profile as type A but it is still difficult to adequately coat the edges, and the top profile is angled to pick up considerably more ultraviolet light than the vertical surface of the board.

Type C is by far the easiest profile for painting, and on most weatherboard houses the bottom angle is bevelled.

Type D weatherboard can run vertically, diagonally or horizontally. It does not have the sharp profile problems of type A and B boards, but if not properly sealed before fixing in place there is easy access for water to get behind the boards because of the square channel pattern between them. Any timber movement will expose unprimed timber areas that can soak up water.

Where boards are fixed other than horizontal, Resene recommends that the full paint system be applied to all sides.

Extracted from the helpful DIY section of Resene’s website.

Top tip

Resene TimberLock is a multi functional timber treatment that improves the dimensional stability of the substrate, as well as improving its fungal, water and ultraviolet light resistance. Its use improves the durability of subsequently applied topcoats. It is especially recommended on Cedar that is to be painted, as well as on old weathered timber.

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Colours shown on this website are a representation only. Please refer to the actual paint or product sample. Resene colour charts, testpots and samples are available for ordering online.   See measurements/conversions for more details on how electronic colour values are achieved.