Treating Timber Decking - The Best Ways to Treat Timber Decking and Exterior Woodwork Explained

Summary: The best ways to treat timber decking, furniture and exterior woodwork. Learn how to treat decking for a long life and a great finish. We review some of the products that you can use and in which circumstances they should be used in order to keep your timber decking, exterior timber and garden furniture in tip top condition all year round.

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Timber decking and garden furniture can be oiled, stained or sealed. There are no hard and fast rules about which you should use, so it is really down to personal preference. We prefer to oil as it brings out the natural texture of the timber, but in certain circumstances this might not be appropriate or the most attractive thing to do.

Treated and cared for decking

Treat Decking to make it last and look great

Whichever approach you take, first it will be necessary to clean the timber and the easiest way to do this is with a power washer for decks (and some larger items of furniture) or a bucket of soapy water, a stiff brush and some elbow grease! A mop, bucket and good scrubbing brush is a great way to clean timber decking. See our power washing project for more information.

There are dedicated products that can be used to clean decking (and keep it clean). These can help to reduce the amount of elbow grease that is needed to get the decking cleaned. It is a great idea for ongoing cleaning as these solutions have chemicals that kill and suppress mould growth. Most of the leading brand names will produce a version of their own decking cleaner, and so far we have found them to all be pretty effective, and much the same in terms of performance.

Dedicated decking cleaner

A dedicated Decking Cleaner is great for rejuvenating decking – available from our online DIY Store

Staining Decking

It is often necessary to stain your decking, having cleaned it and before you treat it. This is not always required and not the subject of this project. For more information on staining decking have a look at our project here.

Treating Decking With Oil

First treat the timber with some kind of universal wood preserver as shown below. This will make sure the timber is unaffected by rot and wood boring insects etc. Please be careful if using preserver near ponds as it is not good for fish!

Decking and wood treatment

Decking and wood treatment against rot and insect attacks – available from our online DIY Store

Most DIY stores these days have proprietary treatment products for decking and furniture and they are almost all derivatives of the following products. All can be used to treat and preserve the timber. The linseed oil is particularly good for hardwoods. Oil should be applied regularly, about 3 times per year, to get the very best out of your decking.

Treating Decking and Furniture with Linseed Oil

Linseed Oil in a very versatile and useful product. It is the extract of the flax seed and can also be known as Flaxseed. Not only is linseed critical to the proper seasoning of a cricket bat, it can also be used as a food additive or nutritional supplement (due to the high omega 3 fatty acid content). It has some be used as a paint binder, the oil in putty, the ‘glue’ for gilding and even the primary ingredient in traditional Lino flooring.

It is very safe to use and has an odour that most people enjoy. The linseed penetrates the wood and does not provide a surface barrier as a varnish would do. It also will allow water to penetrate and therefore can be prone to mildew, which is why we suggest treating the decking or wood with a universal preserver before applying the linseed. Linseed will not provide protection from scratches but it does show the grain of the wood and will weather over time to a very natural look which you cannot achieve with any other finish.

Weathered Decking finished with Linseed Oil

Weathered Decking finished with Linseed Oil

A very common question is, what is the difference between raw and boiled linseed oil and which should I use on my decking? One of the major issues with linseed oil is that take a very long time to dry and before a second coat can be applied. To address this issue additives (mineral spirits, Japan drier, and turpentine) have been mixed into the linseed oil.

Boiled linseed oil has not actually been boiled but has had additives mixed into the raw linseed oil to promote the drying properties of the oil. It is described as ‘boiled’ as traditionally oils had been boiled to alter their properties and this generally refers to the changed properties as if they had been boiled, although the effect has resulted from the solvent additives. Raw linseed oil is simple the unaltered linseed.

You can use whichever type of linseed oil on your decking; the deciding factor is generally drying time. In practice it is recommended to use a boiled linseed as we want to get the job done and admire our handy work!

Linseed oil decking treatment

Linseed oil decking treatment – available from our online DIY Store

Applying Linseed Oil to Decking:

You can apply linseed oil with a rag or a brush. Apply liberally covering all exposed surfaces. Don’t allow the linseed to pool or form puddles but try to get an even layer across all the wood. Some areas of the wood will absorb the oil more quickly; there is no need to be concerned about this and apply a little extra here as the oil is absorbed.

An hour or so after application give the surface a rub down with another dry cloth. This will spread an pooled oil out evenly and give you a better finish in the long run. After a further 24 hours it will be time to apply a further coat if this is necessary. Subsequent coats can be applied in thinner layers, but you should wipe them down as before with a dry cloth after about an hour.

Always follow the application guidelines provided by the manufacturer, as drying times will vary depending on the composition of the oil and the type of the wood. Humidity and temperatures will also have an influence.

Application rates will vary greatly depending on the wood and how ‘thirsty’ it is, but typical coverage would be between 6 to 12 Sq meters per litre. Again, follow the manufactures guidance, but it is not a major issue if you get this wrong, as excess can be wiped away relatively easily and more coats can be applied as required.

Using Danish Oil to Treat Decking and Exterior Timber

Danish Oil is a wood finish made from either Tung Oil or Linseed Oil. Other plant extract oils can be used too (mineral oil, Tung oil, linseed oil, poppy oil, cotton oil, sunflower oil, among others!). It usually consists of two thirds to a half oil, with the balance being varnish. The idea is that you get the benefits of both the varnish and the oil without the disadvantages. It is hard wearing and long lasting without being high gloss and slippery, it allows the wood to ‘breath’ but is also water resistant. It is easy to apply and will dry relatively quickly without a strong odour.

Water on wood treated with Danish Oil

Water on wood treated with Danish Oil

For decking it is recommended that the Danish Oil that you use has a look varnish content as this is what can cause a glossy and slippery finish to your decking. This finish is often desired in furniture or other exterior wood surfaces where in might be a more appropriate choice.

Water on wood treated with Danish Oil

A Danish Oil suitable for outdoor use – available from our online DIY Store

Application of Danish Oil to Decking

You can use either a rag or a brush; we find a rag can be easier, although we do recommend the use of some disposable gloves, and please dispose of the rag safely. Amounts and coverage vary between product and the type of wood that is being applied to so follow the instruction on your chosen product. As a rule of thumb, you should expect that 1 litre will cover between 12 and 15 Sq meters. Drying time between coats will also be affected by humidity and temperature, but leave between 3 and 24 hours.

Danish Oil get its name from the finish that was created for Scandinavian furniture which became popular in the middle of the 20th century. The low sheen finish became popular and the term Danish Oil came into use to describe the effect. It then began to be applied beyond furniture.

All in One Decking Treatments and Varnishing Decking

While we are not keen on varnishing decking, this is an appropriate treatment for some furniture and exterior woods. Varnish will protect the wood, but it will create a glossy and more dangerously, a very slippery surface. Clearly this is not what you want on your decking.

There are, however All in One decking treatments which combine all the elements of a decking stain to colour the wood, the protective qualities a wood preserver and the sealing effect of linseed or Danish oils. In a single application you can achieve a similar finish and protection as you would from the range of products we described about. You are limited in choice, particularly in colour, although the ranges available are getting much better now.

Typical all in one decking treatment

A typically All in One Decking Treatment – available from our online DIY Store

These all on one products are excellent for treating new decking as they will provide a quick and durable finish. They can be harder to match to existing decking when touching up and/or making repairs.

While there is a huge range of products there are no hard and fast rules about which should be used when. Ultimately it comes down to personal preference. This is why we recommend testing a few solutions on some off-cuts of decking to work out what you like and which will suit the environment best.

There is also information regarding the treatment of timber in our treatment of wooden worktops project.

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