Wood brings a trendy and ecological look to the outside of a house. For this reason, many wooden surfaces such as terraces, garden furniture and wooden cladding are flourishing around the house. However, when it comes to outdoor wood, it is exposed to everyday wear and tear (chlorine from swimming pools, stains or rubbing) and to climatic factors such as UV rays from the sun, rain, hail or snow. It is therefore essential to effectively protect the wood to improve its resistance to these damaging factors.
There are many products available for the protection of wood outdoors. We can talk about 3 types of products, each with very particular characteristics: stains, saturators and oils.
But how do you find your way around this multitude of products, each claiming extraordinary properties?
In this guide, we will explain in detail the characteristics of each one, see the advantages and disadvantages, and then we will give you our professional opinion as a wood care professional on the product to be preferred depending on the surface.
Stains are transparent film-forming finishes, i.e. they form a hard film on the surface of the wood but retain the natural grain of the wood. Tinted or colourless, they provide effective protection against rain and UV rays. They must be applied in several coats to obtain lasting protection. The duration of the protection varies between 3 and 6 years for an application of 2 or 3 coats on vertical exterior surfaces. Beware of overly tempting marketing arguments announcing a guaranteed life for 10 years or more. If you read between the lines, you'll soon realise that the guarantee conditions exclude almost all cases of situations usually encountered at home. For example, many types of wood and exposed surfaces are excluded from the guarantee. In some cases the guarantee can also only be valid if 4 coats of primer + 4 coats of finish are applied, which is very restrictive.
The stain is more suitable for vertical surfaces such as shutters, cladding or gates. The application of woodstain is not recommended on horizontal woods such as wooden terraces or stairs, as the protective layer may be prematurely damaged by moisture.
Most of the stains currently available in DIY shops are formulated in aqueous phase (with water). They contain resins called "acrylic", or sometimes "polyurethane", which form the binder, then pigments and additives to obtain the texture suitable for spreading and protection against the development of micro-organisms. There are still so-called "solvent-based" stains, which are highly odorous and flammable but are recognised for their effectiveness.
Stains will give a matt, satin or even shiny finish. The advantage of woodstain is that it preserves the wood grain, even for stained products. Unfortunately, the "feel" of the wood will have disappeared since a smooth film will have been deposited on the surface.
Single coat stains are rarely sold. Some manufacturers venture to do so, but the protective durability is not there. In general, stain is applied in several coats. It is important to follow the recommendations indicated on the canister. Drying times are usually fast, in the order of 2 to 6 hours
Maintenance is fairly infrequent (every 3 to 6 years on average) but, depending on the thickness of the film, it may require lot of work. Indeed, as stain is film-forming, sanding or chemical stripping will be unavoidable to renovate the cladding, shutters or a gate protected in this way.
If you are prepared to go to this effort, stains are a good solution to avoid having to maintain your wood too frequently.
Unlike stains, saturators are non-film-forming protective products, i.e. they do not create a film on the surface. They deeply impregnate and nourish the wood until it reaches saturation point. Whether coloured or colourless, saturators retain the wood look and feel perfectly. Their rapid drying and ease of application and maintenance make them highly sought-after products for outdoor wood maintenance. The saturators can be applied to all outdoor surfaces: decking, cladding, garden furniture, shutters, pergolas, ....
Unlike stains, saturators are non-film-forming and are therefore suitable for all exterior surfaces, whether vertical or horizontal.
Saturators are products formulated in an aqueous phase, i.e. water-based. They contain a synthetic (acrylic, alkyd) or semi-synthetic (alkyd may be partly plant-based) resin that penetrates easily into the wood and dries quickly. In addition, pigments are added for UV protection and additives to facilitate application.
While stains will give a satin or gloss finish to the wood, saturators will preserve the matt appearance of the wood. Depending on the colour of the product, the original colour of the wood will be preserved or revived and very beautiful results will be obtained on resinous wood cladding or exotic wood terraces, for example.
The application of the saturator is very simple. A coat of saturator is applied by brush or roller to clean, dry and dust-free wood. A second coat may be applied in the case of very absorbent wood. Be careful, if you feel the need to apply 3 coats, it is because the saturator you have purchased is of low quality. For advice on how to apply a saturator, you can consult our guide How to maintain a wooden deck ?
The saturator is the easiest protection product to maintain because it is not film-forming. Indeed, there is no need to sand or strip before applying a maintenance coat. A simple cleaning of the surface, or even the application of a wood grey remover for greyed wood, will suffice before applying a new protective coat.
Maintenance is still more frequent than for stain. About 1 to 2 years for horizontal surfaces and 2 to 5 years for vertical surfaces for a good quality saturator.
Like saturators, oils also work by penetration. This is known as a saturating oil. These two types of product are similar in terms of their appearance and application method. Their difference lies in their composition, where the plant-derived part is superior for a protective product called "oil". Indeed, it is interesting to opt for an oil when you are looking for the most ecological product possible. However, we would like to warn you on this point because the "ecological" or "natural" argument sometimes hides surprises. It is important to read the composition carefully.
Like saturators, oils impregnate the wood and do not form a film on the surface. They are non-film-forming. They can therefore be applied to all types of exterior surfaces, both vertical and horizontal.
So-called "oil" protection products are therefore mainly composed of an oil or a mixture of vegetable oils (linseed, soya, Chinese wood oil, etc.). The pigments will reinforce the UV protection outdoors. A siccative is often used to accelerate drying. Finally, to protect the oil from microbiological attacks, biocide additives are added. This allows them to resist longer outdoors but unfortunately make them lose their ecological characteristics.
The traditional linseed oil, or linseed oil/terebenthine mixture, is very quickly degraded outdoors. Between 3 and 6 months, the treated surface darkens. It is not recommended for outdoor use.
Oils have the particularity of giving a "wet effect", or "oiled" look, which darkens the wood slightly to enhance the grain. This effect is sought to "warm up" the tone of the wood and the result is often very satisfactory. The matt appearance of the wood is retained after the application of the protective oil.
The application method is identical to that of the saturator, except for certain oils which must be wiped off after each coat. Wiping makes the work more involved than applying a saturator. Also be careful with oil-soaked cloths, which can self-combust. They must be soaked in water before throwing them away.
Mainly based on vegetable oils (linseed, soya), protective oils tend to be washed out more quickly by the weather than saturators, which is why they do not last as long and require frequent maintenance. The development of "biofilm", characterised by the proliferation of black spots and patches on the surface, is also faster. This again requires more frequent maintenance than a saturator. Generally every 6 to 12 months for horizontal surfaces and 1 to 2 years for vertical surfaces.
Of the 3 types of products mentioned in this article, 1 product is film-forming, the stain, and 2 are non-film-forming, the oil and the saturator. To make your choice, we advise you to take into account the elements listed in the table below, rememebeing the usage, the finish, the frequency of maintenance, and the composition of the product.
|Water or solvent-based||Matt, satin or glossy
Colourless or coloured
2 to 4 coats
|Vertical exterior surfaces: cladding, shutters, gates, pergolas||
Every 3 to 6 years
Difficult maintenance: sanding
|Saturator||With water||Matt to satin
Colourless or coloured
1 to 2 coats without wiping (easy)
|All vertical and horizontal supports outdoors||
Every 1 to 2 years for horizontal surfaces (terrace)
Easy application and maintenance (without wiping and sanding)
|Oil||In water emulsion, 100% oil or solvent-based emulsion.||Matt
Oiled effect ("wet")
1 to 2 coat
|All vertical and horizontal supports outdoors||
Every 6 - 12 months for horizontal surfaces (terrace)
Natural look with oiled effect
Difficult wiping required for application on terraces and claddings
To preserve the natural appearance of the wood and to have easy and less expensive maintenance, non-film-forming products are preferable.
Both the oil and the saturator work by penetration, allow for a very high quality finish, and are good solutions if you want to use an environmentally friendly product. However, it turns out that the saturator will require less frequent and easier maintenance if necessary.
Therefore, for many aspects (ecological, ease of application and maintenance, a finish close to the original wood), we recommend applying a saturator rather than an oil or stain. Depending on the type of wood, there are suitable saturators available. For example, if you have autoclaved wood, we advise you to apply Autoclave Wood Saturator SBA600 . On exotic wood, the application of Exotic Wood Saturator SBE600 is recommended. For other types of wood, the Siding Saturator SB600, the Terrace Wood Saturator ST600 or the Garden Furniture Saturator SJ600 will be perfectly suitable..