How to Keep Exterior Wood Protected for a Decade

07.07.2015

When it comes to exterior woodcare, protection and a beautiful finish should go hand in hand. Dulux Trade Woodcare products are formulated to both defend exterior wood from the elements and everyday wear and tear, and enhance the material itself.

Now, looking after exterior wood is even less labour intensive, as the Dulux Trade Quick Dry Woodstain and Opaque ranges have been upgraded from six years to 10 years protection. As well as exceptional durability, these products also have an excellent spreading rate of up to 20 m2 per litre, further adding to their cost-efficiency.

Andrew Roser, Woodcare Brand Manager at AkzoNobel explains: 'With improved durability of up to 10 years protection, Quick Dry Woodstain and Quick Dry Opaque products bring outstanding levels of protection and aesthetic appeal to exterior joinery.'

This new longer-lasting protection means Quick Dry, water-based products now match the durability of traditional, solvent-based woodcare products, giving you and your clients even more reason to make the switch from solvent-based to water-based products. The multiple benefits of Quick Dry ranges include low odour, lower environmental impact, easy clean-up of brushes and equipment and (of course) quick drying times.

Best practice for woodcare application revolves around preparing your surfaces properly, so make sure you take the time to cover off the following 10 golden rules to see the longest-lasting results:

1. Clean & degrease

Timber can be resinous or oily, but don't forget that surface dirt and grime needs to be removed before any coatings are applied, too. Thorough cleaning with hot soapy water and a nylon scrubbing brush will ensure these contaminants are removed and ensure a clean surface. Make sure all dirty residues are rinsed off with clean water, and the surfaces are allowed to dry fully before any coatings are applied.

For hardwoods that contain high levels of oils and gums (e.g. Teak, Cedar), and softwoods that contain high levels of resin (e.g. Pine/Redwood), always degrease the bare timber before coating by wiping over with a clean cloth dampened with methylated spirits. Don't use white spirit which will leave a 'greasy' residue and spread any contamination. Do change the face of the cloth frequently to avoid re-contaminating the surface.

2. Moisture content

Don't apply coatings to wet timber as the adhesion will be poor and the coating will peel and flake. Timber should have a moisture content of around 15-18% for exterior use.

3. Treating weathered timber

Silvery-grey timber fibres are a sign of timber that has been 'denatured' by weathering. These fibres are absorbent but loosely attached to the main body of the timber, so if they are not removed before coating, the stresses of external exposure will cause them to become detached from the surface, taking any coating with them - one of the main causes of peeling or flaking coatings. If timber has been exposed to sunlight for more than four weeks it will require mechanical sanding of the surface in preparation for a coating.

4. Glazing materials

We do not recommend the use of linseed oil putty or modified non-setting compounds in conjunction with our wood protection systems as the long-term performance of these compounds is inferior. Instead, use an acrylic sealant that does not have to be over-coated to prevent it from drying out. If using silicone, always apply carefully after all decorating is completed because no coating will adhere to it.

5. Unsound coatings

If the coating is in poor condition, brittle or loose and flaky, with areas back to bare timber, it's advisable to remove all coating back to a firm edge. This can be done using chemical strippers (always ensure residues are removed, and where necessary the treatment is neutralised) or sanding (removing all dust), or a combination of both. Always use a base stain or primer to patch in this area before applying finishing coats. This will improve the adhesion and performance of the coating and, in the case of translucent finishes, prevent unsightly lighter patches in the finish.

6. Decay & blue stain

Decay and blue stain are both the result of a fungal infestation. Blue stain feeds on the sap in the timber, and cannot be removed, only disguised. If it is not treated, it will push through any finish, accelerating breakdown of the product on the surface. A blue stain inhibiting preserver should be used, followed by a dark stain or opaque finish to obscure the discolouration. Meanwhile, decay or rot is caused by a fungus which actually consumes the timber fibres. Any evidence of rotten timber should be cut out and exposed wood preservative treated. Use a resin-based filler in any voids (but be sure to use fillers specifically designed for use with timber), or splice in solid wood where appropriate.

7. Sharp edges

Where two faces meet to form a sharp corner, any applied coating will naturally pull away from the edge, leaving a thinner coating film than a flat surface. As a result, bare timber is often exposed more quickly as the coating gradually weathers away, leading to an accelerated breakdown of the coating. Therefore it's recommended that sharp edges are rounded to the British Standard 3mm minimum radius (often called a 'pencil round'). To areas where this is not possible and an opaque product is being used, an extra 'stripe' coat may be applied to the edges. This will not, however, offer the full protection normally achieved by a coating to a flat surface or rounded-off edge, and should only be used where there is no alternative. For aesthetic reasons, this method is not suitable for use with translucent coatings.

8. Mould & algae

Mould or algal growth to the surface of timber is indicative of a high moisture content, and should this occur to joinery, it is obviously important to check any possible points of moisture ingress such as defective glazing, and take corrective measures. To timbers which are surrounded by vegetation, algal and mould growth is likely to re-occur, but the frequency of this can be reduced by the use of a proprietary fungicide, or a bleach and water solution. Either of these will kill the airborne spores, which a simple wash down with detergent and water will be unable to do.

9. Knots & resin

Resin exudation is natural and highly unpredictable, and varies depending on both timber species and timber grade/quality. The traditional answer was to apply shellac to 'seal' in the resin. However, many years of research and on-site experience has shown that this method is not effective, as once the resin pressure builds up to a certain level, it blows off the knotting and subsequent coatings. This is one of the major causes of paint failure to claddings.

Moisture vapour-permeable (sometimes referred to as microporous) finishes such as woodstains attempt to deal with the problem of the finish in a different manner by allowing resin to filter through the finish without blistering or peeling, hence full protection is maintained. In the short term, resin exudation tends to look unsightly, but within a year or so the excess resin normally becomes exhausted and exudation ceases.

10. Ask for help

If in doubt, ask for help! Contact the AkzoNobel Technical Advice Centre on 0333 222 7070 or email duluxtrade.advice@akzonobel.com.

Find out more about Dulux Trade Quick Dry Woostain and Dulux Quick Dry Opaque, or watch our video guides on the 10 Rules for Successful Woodcare Application.