Special Finishing and maintaining wooden exterior walls

PROTECTING AND EMBELLISHING WOODEN WALL CLADDING

HOW DO WE PRESERVE THE NATURAL LOOK OF WOODEN WALL CLADDING?

Photo – Blanchon

It is clear that the demands made of a wooden wall cladding finish are not entirely the same as those for wooden terraces. We won’t be walking on our wall, so the demands in terms of wear resistance are completely different. Obviously, wall cladding is exposed less to all sorts of potential mechanical dangers such as falling items or chemical products. Nor do you spill wine or coffee on a wall. Wooden wall cladding has some natural enemies, so the wood has to be protected and maintained, but those enemies are found elsewhere and mainly in the form of the weather conditions.

Light, air, water, and bugs Ultraviolet light, oxygen, and water together form the main cause of ageing and possible wood rot. In a photochemical process, sunlight breaks up the dark-coloured lignin, one of the main components of wood. The light-coloured cellulose, the other component, is left behind on its own. The fact that the wood turns grey shows that the colour of the cellulose will prevail. What we perceive visually as ‘greying’ or ‘ageing’ is actually a microscopically thin layer of wood decomposing. The greying can be darker or lighter, depending on the surrounds and the extent of pollution in the air. Apart from those atmospheric conditions, there is also the threat of living organisms. The major threats to outdoor wood are wood worm and wood rot. The wood worm is a larva of the furniture beetle. The designation ‘worm’ also refers to the larvae, since the wood worm is basically a beetle. The wood worm lives in the wild, especially in trees with hard wood, such as oak and fruit trees. Wood rot is a fungus which mainly affects wood exposed to (excessive) damp. In some cases the fungus is visible. Sometimes, wood rot betrays itself by the fact that the wood surface turns brown and crumbly or looks dirty white and spongy. The fungus often pene trates to the inside of the wood via the ends, such as the underside of a pole, the place where two beams touch each other, the connecting points of window frames, and such like. Wood which is often exposed to wind is particularly vulnerable.

Protecting and embellishing ‘Protecting’ is merely one aspect of a treatment for outdoor wood. We also want our wooden wall cladding to look nice and stay nice. The choice of wood sort is a first step to that end. Some wood sorts are simply nicer than others, even if that is clearly just a matter of taste. The most coveted wood sorts are usually also the most expensive ones. They do have the advantage of being ‘more durable’ than cheaper sorts. One of the aesthetic reasons for treating outdoor wood is to counteract the aforementioned ageing. Some people like the look of ageing wood, yet we do know that it is an ‘expression’ of gradual decay. Embellishment is possible by applying a product to counteract the ageing. This achieves a dual objective. The more you use colours, the more effective the protection from UV light. The addition of pigments hinders the penetration of sunrays.

Protective products The products used for outdoor applications have to be weatherproof, water vapour permeable, and preferably pigmented. The water vapour permeability is important so that the damp inside the wood can migrate. The pigmentation of transparent products protects the underlying wood in turn from the UV rays of the sunlight. The usual advice is to use light shades (e.g. light oak) and to respect the prescribed coat thickness. Excessive pigmentation (e.g. rosewood, ebony, or dark paints) is also harmful because the wood surface might get too hot and the woodwork may crack or warp (e.g. opening parts with large dimensions or sliding windows). Below we give a description of the main products which are available on the market for the finish of wall elements (source consulted: BBRI): - Stains contain a low content of resins and therefore form a thin film with a certain transparency so that the structure of the wood is still visible. These are the so called non-film or semi-film forming finishes. They offer a longer lifespan in proportion to the amount of dark pigments with better UV resistance that they contain. In

Belgium these products are identified using the homologation code

C2 (general) or C3 (wood with sufficient natural durability; cf. STS 04.3). - Top coats contain more resins. These products are generally opaque i.e. the relief of the wood structure is still visible, but not the veins.

They are identified using the CTOP code (cf. STS 04.3). - Paints can contain a very high content of resin which covers the structure of the wood fully; the so called film-forming finishes. The use of darker paints is not recommended since the film absorbs the heat of the sun. This results in the surface temperature rising sharply (from 60 to 70 °C) in the summer and, in some cases, the resin from certain wood sorts separates, the coat of paint cracks, or the wood splits. - Natural or modified oils (urethane or acrylic) are transparent and more or less coloured products, but with no pigments. A finish using natural, non-modified oil for outdoor applications is not recommended since it creates a breeding ground for fungi and algae.

Moreover, oils are used a lot in the production of alkyd resins for stains and paints.

Film-forming varnishes are not considered suitable by the BBRI for outdoor use. Since they do not contain any pigments, they are extremely susceptible to photochemical dissolution of wood under the influence of sunrays and therefore they flake very quickly.

What’s on the market ?

Blanchon Blanchon believes that some wood sorts such as red cedar, douglas, and meleze can remain untreated. Other wood sorts can be left untreated after they have had a preservative treatment. The application of a protective coat is usually designed to preserve the original colour of the wood. Before the new generation products existed, ‘saturation’ was the only possible means of protection. Blanchon has a double assortment here. The Blanchon Wood Saturator is a saturator based on the traditional formula with oil which was coloured or clear (Saturator and Single-coat Saturator). For some years, Blanchon has also offered the Ecological Saturator which is in the Environment Quality Line and scores well on all points. This can also be applied to exotic wood sorts immediately after the fitting. Also in this range Blanchon offers the Blanchon Ecological Opaque Saturator. Nowadays, with the new anti-UV systems, you can apply a finish/protective coat to preserve the original colour of the wood perfectly. These products counteract UV on the basis of new ‘agents’ so that the lignin is not affected by sunrays.

The Colourless Anti-UV System is a colourless protective system from the effects of sunlight on the wood. Whilst protection from UV light is related traditionally to pigment additives, this system is therefore colourless. A new type of protection is Weatherproof Oil which provides a shade of colour, but leaves the wood grain visible. Finally, there are the new glazers Tech Wood and All Wood Ecological Stain, which is based on new generation resins and is meant for all sorts of wood.

Briançon

Briançon believes that wall claddings in horse chestnut, oak, douglas, and meleze can be left untreated perfectly well. A treatment can be applied to counteract the natural ageing. The best products for that are azures, paints, or saturation products. It might be necessary to repeat such treatments, depending on the level of exposure to the weather. Briançon presents Special Outdoor Oil for Terrace Wood (‘Huile Extérieur Spéciale Terrasse Bois’). This is an impregnation and protective product for all sorts of wood (native, exotic, coniferous, and deciduous trees). It is excellent for new wood. Azure Impregnator (‘Lasure Imprégnante’) is also a wood protection product for outdoors with UV protection. It is waterproof, odourless, and fast-drying and provides protection deep down.

Chimiver

LIOS Sundeck Wood Oil is an outdoor wood impregnator particularly recommended for the treatment of outdoor wooden floors (swimming pool edges, verandas, walkways), window and door frames, fences and canopies made of wood. It contains natural and synthetic oils, with the addition of UV ray absorbers and special anti-ageing ingredients against the wood decay. It doesn't crack. Also available in LIGHT version,

which doesn't alterate the natural colour of wood, particularly indicated for the treatment of south-american species (i.e. IPÈ Lapacho, Tobaco etc.) and other similar types of outdoor woods painted in autoclave (usually green colour). Doesn't degrade rubbers and expansion joints. LIOS Sundeck Soap is a nourishing cleaner used to clean outdoor wooden floors. Used regularly, keeps a natural wood appearance, avoiding wood decay caused by adverse weather conditions. It efficiently removes dirt, traces of chlorine, salt etc.

Osmo

For the treatment of exterior wood, Osmo offers numerous products for different purposes: Osmo Country Colour is ideally suited for an opaque, biocide-free and particularly durable finish. Osmo One Coat Only HSPlus is also free of biocides and, like Osmo Country Colour, is suitable for children's toys. After just one coat, the wood is optimally protected. Osmo Natural Oil Woodstain protects wood against mould, algae and fungal attack and contains biocides. All products are available in various colours.

RIGO Verffabriek

The master oil makers of RIGO Verffabriek have been making ROYL floor oils from 100% vegetable oils for almost 40 years. ROYL OUTDOOR was developed and added to the ROYL range for the protection of exterior wood. Just like ROYL OIL, Outdoor protects the wood from the inside out. Finishing your wood with ROYL OUTDOOR will enhance its durability and longevity by impregnating and nourishing the wood, seeping deep into its pores and polymerising into a tough, dense protective layer inside the wood. ROYL OUTDOOR gives wood a beautiful, highly water and dirt-resistant surface. ROYL OUTDOOR can be tinted with separate colour pigments. Besides, adding a colour pigment will also protect the wood against aging caused by sunlight. ROYL OUTDOOR comes in 23 authentic wood colours. Treat your wood regularly with ROYL OUTDOOR for long-lasting protection and to prevent weathering. ROYL OUTDOOR can be used for both vertical and horizontal surfaces.

Safe for humans, animals and plants (when dry) A c c o r d i n g t o D I N E N 7 1 . 3 ; f a s t t o p e r s p i r a t i o n a n d s a l i v a

OSMO: THE SOLUTION FOR YOUR INTERIOR WOOD THE SOLUTION FOR YOUR INTERIOR WOOD

Oil Stain Wood Wax Finish