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I was prompted to write an article on deck maintenance and deck sealing this week as we had a small quiet patch and as a “filler in” we sanded and sealed a picnic table, repaired a broken ball and claw foot and a leather couch and this reminded me to write this article.

Deck maintenance and deck sealing is always a question asked when quoting on new decks. Clients want to know that if they invest this kind of money in their property, will it be expensive to maintain in subsequent years. The simple answer is no, but if not correctly sealed in the beginning, then it can become an expensive and time-consuming task each time it needs to be maintained. The question is also sometimes asked when choosing between timber or composites.

There are many ways to seal a deck. “Finishing” is the correct term for it and this term also applies to all other timber products. Varnish, polyurethane, oil, sealer, paint etc. are all products used to “finish” a project. When it comes to decks there are certain products to stay well clear of. Because a deck lives outside in the hot African sun, any finish that dries on the surface of the timber will result in problems once it starts to degrade. All finishes will degrade and it is therefore very important to stay away from those that dry on the surface. It is common sense that anything that has dried on the surface will have the tendency to lift, either by cracking, flaking or peeling. When it comes time to maintain the deck, one will either have to sand it all off, or lightly sand it and re coat it with the same or similar product that was used in the beginning and live with a patchy finish. Therefore varnish is a big no-no. Polyurethane, although very durable and hard will also crack and flake and is better left for the purpose it was intended, indoor finishing on cupboard tops etc.

So that leaves us with those finishes that soak into the wood, nourishing them and when they degrade will not peel or flake because they have not dried on the surface. Simple hey? Not so. There are products which contain higher wax contents than others and although still classed a timber sealer, tend to soak in and leave a waxy film on the surface. This waxy film (or coating for want of a better word) will also tend to go blotchy once the sun does it work on it and will therefore also require some degree of sanding. Before we carry on, it is virtually impossible to sand the entire coating off. The electric sanders do not reach all corners, especially on a balustrade. The belt sander, rotex sander and any other sander will be too wide for the deckboard. Because there is a gap between boards, to allow water to drain away from the deck, the surface of the deck is not perfectly flat. So one will need to tilt the sander left and right as they sand down the length of the deckboard in order to remove the whole coating. Try it, it will cure you of varnish for outdoor products. The corners where the machines cannot reach will need to be sanded by hand and your labour bill will be more than erecting a new deck. I tried in my early days and learnt the hard way.

Oils can be used with some success. Raw linseed oil will take weeks to dry as it is raw and completely natural and therefore needs to soak in completely before you can walk on it. Also when the sun bakes down on the deck it will start to get soft and can become very hot to walk on. Boiled Linseed Oil will dry quicker as it contains additives that help the drying process but will still take a few days to dry. In the meantime the dog will run on the deck and leave muddy footprints that will dry into the surface. Again a lesson I learnt when experimenting with my own deck. Boiled Linseed Oil is not really boiled, it just means it has additives to help it dry faster than raw Linseed Oil. So for all intents and purposes it is a sealer. Danish oil will work well. I have not finished a deck in Danish Oil, but have used it quite successfully on outdoor furniture.

So now that we’ve eliminated the definite no no’s, we are left with timber preservatives or penetrating finishes. These are very viscous, almost as viscous as water. They are easy and quick to apply, no runs, no streaks and they go on quickly as they soak right into the wood. Seeing as they soak right in, they cannot flake or peel as there is no coating that has dried on the surface. We use a product manufactured by Timberlife called Satinwood 28 Base. This is a product designed for woods of low porosity. They also manufacture one for woods of high porosity. Don’t get them mixed up or the sealer will disappear right through your pine deck in a day or two or sit like a coating on your balau deck.

At least 2 coats are necessary on the first application and because the deck is new, one will need to reseal it about 3 to 4 months later. After the first year this maintenance interval will increase to every 6 months and the older the deck gets the longer the maintenance interval will become. The deck will slowly become saturated (well almost) with the sealer and it will last longer. It comes in clear and one can add a tint of your choice. They recommend that you use at least the lightest tint as the tint contains stabilisers which slow down the degradation process due to UV in the sun’s rays.

Even though it will need to be done every 3 to 4 months in the first year, the process is simple. Wash the deck and reseal. No need to call in the professionals and pay their rates. No need to sand and no paint stripper required. DIY it on a Saturday or Sunday or get your domestic helper to do it.

Timberlife also supply a product called Ultra Care Gold. This has a higher wax content as mentioned above and is not suitable for horizontal deck surfaces but works very well on the vertical posts of balustrades. They also sell Deckwash which is used to wash the deck on a monthly basis and again nourishes it and leaves it looking new for longer. It is inexpensive and well worth using. Simply mop it on and mop it off.

So in short stay away from finishes that dry on the surface. Stick with those that penetrate the timber and nourish it.  In the case of a deck that has been coated with a coating that has dried on the surface one can either lightly sand and re-seal with the same coating or if budget allows one can remove the coating, by using paint stripper and a high pressure cleaner. Stick to a maximum of 150 bar pressure otherwise the timber can be damaged. I’ve successfully removed coatings on decks with this technique. It is messy, uses a fair amount of water and a considerable amount of paint stripper. Depending on the thickness of the coating, one might need to apply the paint stripper more than once and blast it off with the high pressure cleaner.

High pressure cleaning can also be used to clean the deck before resealing it with Satin Wood 28 Base, but is often not necessary. I say not often necessary if you catch it before the balau starts to “grey”. Balau will tend to turn a grey colour if left unsealed or if the sealer that is there reaches a point where it is almost completely degraded due to the sun’s UV. If this occurs and the deck is then resealed, it will go very dark, regardless of what tint you use. The grey colour is in fact a thin layer of black algae. You will find that it is quite slippery when wet. This black algae needs to be removed first before resealing. Again Timberlife, and Woodoc, and some other manufacturers supply a product that will remove a lot of this by bleaching it. Timbrite is the one I use and it can be scrubbed on with a brush and then hosed off. It won’t take all of it away, so high pressure cleaning is a quicker way of getting rid of it. I would suggest scrubbing Timbrite on with a brush, then high pressure cleaning it off with 150 bars of pressure. This will renew the wood back to almost its original colour.

Leaving a balau deck unsealed will not necessarily speed up the rotting process. Balau is extremely durable as it contains natural resins and oils which repel water and the toxins in it discourage insects. So sealed or unsealed it will still last for years. Some prefer it unsealed to give it the natural grey look, but take note that if you then decide to seal it, clean it first as described above.

All the above also applies to outdoor furniture or any other timber that is in direct contact with the sun’s rays, especially those that are in the horizontal plane as they are getting more direct sunlight than the vertical pieces.

Timberlife are of course not the only ones who sell these products. They can be commonly found in hardware stores (Dulux, Woodoc and Plascon), but buying from the manufacturer is of course cheaper, but a bit more effort is required than popping in to your local hardware store.  All of them do pretty much the same job.

Good luck and remember that a deck is a living thing, nourish it, feed it and it will reward you.  If you’re feeling lazy, not interested in DIY or simply don’t have the time complete this form and I will submit a quote to maintain your timber deck.  Or you can reach us 082 496 5444.