Exterior wood or interior wood
This is the first and most important distinction. Wood outdoors, that is terraces, structures and garden furniture, is exposed to water, sunlight and changing weather. It needs protection that stands up to these conditions. Wood indoors, for example panels or furniture, is protected mainly against moisture, dirt and stains.
So choosing the product starts with the question of where the item is and what it is exposed to. A product for indoor use will not cope with rain, and an exterior product is needlessly strong where gentle protection is enough.
Wood types and what follows from them
Wood is not all the same. The species and the state of the surface affect how strongly an item absorbs the product and how quickly it needs refreshing.
- Softwood, for example pine or spruce, is usually more absorbent and common on terraces and in structures.
- Hardwood and tropical wood are often denser and less absorbent and take the product differently. A test matters especially here.
- Old, grey exterior wood usually needs washing first, and sometimes sanding, to expose healthy fibre.
- Previously painted or varnished wood often will not let a penetrating impregnation through until the old, sealed layer is removed.
Tip
Always start with a test on an inconspicuous spot of the specific item. Two boards from the same terrace can absorb differently, and a test immediately shows the colour, absorbency and rough consumption.
Preparing the surface
The wood must be clean, dry and free of grease. Old, grey or dirty surfaces you wash first and sand if needed to expose healthy fibre. A clean and absorbent surface takes the impregnation better, and the protection goes deeper. General rules for preparing the surface we describe in the guide on preparing the surface.
Tip
If the wood was previously painted or varnished, check whether the new product is suitable for such a surface. A penetrating impregnation needs an absorbent base, and a sealed layer may simply not let it in.
Applying the impregnation step by step
- 1Do a test. Apply the product to an inconspicuous spot. You will see how it changes the colour and how the given wood absorbs, before you tackle the whole item.
- 2Apply along the grain. Guide the brush along the fibres. The product then spreads evenly and goes where it should.
- 3Work in thin coats. A thin coat penetrates better than a thick one. Excess gathers on the surface, dries longer and the result is uneven.
- 4Keep the interval between coats. Wood is usually treated in several coats. The number of coats and the drying time between them is on the product label.
Note
Plan outdoor work for dry days above freezing, with no rain in the forecast. A freshly applied product washed off by rain will not bond properly with the wood.
How much product you need
The absorbency of wood can vary a lot, even within one item. That is why it is best to estimate consumption after a test and then confirm it with the consumption calculator available with every product. The coverage of the pack we state on the product data sheet.
The most common mistakes when impregnating wood
- Applying to damp or dirty wood, so the product does not reach where it should.
- One thick coat instead of several thin ones, which leads to streaks and longer drying.
- Skipping the test and being surprised by the colour after coating the whole item.
- Working outdoors just before rain or on cool, damp days.
- Applying a penetrating impregnation over an old, sealed layer that will not let it in.
How to care for wood after impregnation
Protected wood keeps working and is exposed to the conditions, so it is worth checking it from time to time. On a terrace and garden furniture, watch the most exposed spots, that is edges, board ends and horizontal surfaces where water collects.
The signal to refresh is that water no longer beads on the surface and soaks in, and the wood starts to grey. Refreshing usually means washing, drying and applying another coat. How often it is needed depends on the exposure and the product, so you will find the durability on its data sheet.
Frequently asked questions
Does the impregnation change the colour of the wood?
Colourless impregnations keep the natural look. Some coatings can slightly deepen the colour, giving a slightly wetted wood effect. It is best to check this with a test.
How often should I refresh exterior wood protection?
The signal is that water no longer beads and soaks in. How quickly this happens depends on the exposure and the specific product, so you will find the durability on its data sheet.
Can I impregnate an old terrace?
Yes, after thorough cleaning, sanding if needed and drying the wood. On a neglected terrace start with washing and only then apply the impregnation. See also the guide on cleaning and protecting a terrace.
What do I apply the wood impregnation with?
Most often with a brush, which works the product well into the structure, especially for the first coat. On large areas some people also use a roller or sprayer.
Does wood need sanding before impregnation?
New, smooth and clean wood usually does not. Old, grey or previously painted wood often does, because sanding exposes healthy, absorbent fibre and improves penetration.
Can I impregnate wood in autumn?
Yes, as long as it is dry and above freezing and the forecast shows no rain during the drying time. Cool, damp days extend drying, so choose stable, dry weather.
