What is the best way to clean my teak deck?
The simple answer is carefully! Never use a pressure washer or a stiff brush. When pressure washing or scrubbing teak the brown staining to the water that is running off is not dirt, it is the wood itself that is being washed away.
Teak is one of nature’s best natural materials for decking. It has good non-slip properties and is particularly rot resistant due to the natural oils and minerals in its tissues. This has led to the timber being grossly over harvested for both house and boat building materials. For example, the area of natural teak forest in Thailand decreased from 2,324,300 hectares in 1954 to about 150,000 hectares in 2000 (Source: UN Food and Agriculture Organisation).
The felling of naturally grown teak has been banned in all countries and only Forestry Stewardship Council (FSC) forestry grown teak is now legally available. This is fast growth timber developed by advanced tissue culture which allows teak trees to mature in less than 15 years, compared with over 40 years for traditional natural growth teak.
A tree’s growth rings are made up of alternate bands of fast growing springwood and slower growing summerwood. There is no growth in the other seasons. The springwood is a wide band and is light in colour; it is relatively soft and has a thin walled cellular structure. Summerwood is a narrower, darker band and the cell structure is much stronger. It is these alternating coloured bands that create the attractive grain pattern in the face of the timber. In currently available fast growth teak the springwood bands are wider and softer due to the advanced growth rate making it particularly vulnerable.
The use of pressure washers or deck scrubbing has the effect of scouring out the soft springwood leaving the harder summerwood and the caulking as raised ridges. This raised grain will then be rapidly eroded by foot traffic. For this reason a modern manufacture of teak product or decking should never by cleaned using a pressure washer or by aggressive scrubbing along the grain. Modern ‘kit’ decks consist of thin veneers of teak laid over a plywood or an epoxy scrim base. The teak veneers and shallow caulking seams can soon be lost if badly treated.
If sanding off is necessary, it should be very light orbital sanding or across the grain. It can also be cleaned a chemical oxalic acid cleaner. A teak oil should then be applied which will retard the drying out and dying off of the cellular structure. The pale yellow/tan colour seen when the vessel was new is the sign of freshly cut wood. It is natural for the wood to age to a silver/tan colour. To try to maintain the ‘new’ wood look to the teak is to slowly destroy it and the cost to replace a teak deck to a 36ft yacht can be well into five figures.
