Any decking will benefit from regular cleaning although the frequency of this will depend on the sort of usage to which the deck is subject.
Occasional brushing with a stiff broom will normally be adequate for most decks to remove dirt, dead leaves or any slight surface growth in areas where there may have been little wear. The brush should be stiff enough to remove any dirt that may have accumulated in drainage grooves or gaps but not stiff enough to damage any applied surface finish.
Brushing the deck regularly will not only maintain the appearance but will reduce any risk of slipperiness developing from surface growth, engrained dirt, or standing water accumulating due to blocked grooves or gaps between the boards.
Cleaning public decks is frequently carried out by mechanical brushes but rotary brushes are less effective than the cylindrical type in cleaning dirt from grooves and gaps. One advantage of running boards along the deck, rather than across, is that the grooves and gaps can be more easily cleaned by machine. If coarse fibre or wire brushes are used these will tend to remove any surface finish very quickly and can seriously scour the surface even of dense hardwoods. It is important to check that an appropriate brush stiffness is chosen.
On large decks for public use it is especially important to keep the drainage grooves clear because even with clean drainage grooves it takes longer for any surface water to drain away from a large area.
If a non-slip surface finish is applied, or there are non-slip inserts in the grooves, particular care must be taken with any mechanical cleaning to ensure that the surface finish is not removed or the inserts dislodged by the brushing.
It is not advisable to wash down timber decks with large quantities of water or hoses because there is a risk of wetting the boards sufficiently to cause some moisture movement. This could affect the life of any surface finish and lead to increased surface checking when the boards dry in the sun and shrink. However cleaning with a high pressure hose which combines air with a small quantity of water, will dislodge dirt effectively without excessively wetting the wood.
Local soiling and surface growth can usually be removed by mild detergent solutions but if stains are more deep seated on unfinished boards it may be necessary to use specialist deck cleaners which remove dirt, algae and mildew. If using dilute household bleach, the effect should be tested to determine the appropriate strength before it is used in any quantity on the boards. If the stains are from chemicals or metals and still resist this treatment it may be necessary to use special products available for deck restoration which can generally remove quite deep seated stains.
To avoid uneven bleaching, or variation in the colour of a stain finish, it is advisable to occasionally move around any furniture, or other objects, kept permanently on the deck. Any planters or plant pots should be stood on metal trays so that watering does not result in the deck under the pots being permanently wetted, leading to discolouration and mould growth. If the drip trays are supported on battens the top surface of the deck will also be well ventilated.
Tightening fixings and re-surfacing
After the deck has been in use for some time it may be necessary to carry out two forms of maintenance.
The first is to ensure that all the boards are firmly held down. Shrinkage and sometimes wear can result in the loosening or 'popping' of fixings. Nails should be driven home flush to the surface of the boards, and screws tightened as necessary.
Occasionally it may be necessary to replace individual boards that may have been distorted or become more worn in heavily used areas of the deck.
Besides tightening the deck fixings it is advisable to also inspect any bolted or screwed connections in the sub-structure which may have become loose through shrinkage of the wood, and tighten these as necessary. It is advisable to first do this check about six months after the deck has been completed by which time any substantial shrinkage in the wood should have taken place.
The second form of maintenance would normally only be required for unfinished decks where the surface may have become encrusted or worn over time. If the decks are of unfinished hardwood occasional mechanical scouring with wire brushes or sanding will remove mould growth, loose material, engrained dirt or surface staining but it is important to avoid scouring or sanding to the extent that the surface is excessively worn down or, alternatively polished, to a level that would increase slipperiness of the surface.
Alternatively, the use of specific timber deck cleaners will remove growths, clean and may brighten greyed timber.
Re-finishing
Any surface finish will require regular inspection and occasional re-coating. Clear moisture resistant coatings should preferably be re-applied annually but pigmented stains will last several years (depending on the product, the quality of application, the exposure and usage of the deck). It is important that the deck and the grooves and gaps between boards are completely cleaned before the application of a new coat of stain.
If the existing stain has broken down to the extent that the wood has begun to turn grey in places, it is also important to brush away any loose fibres from the surface or treat with a cleaner before re-applying stain.
The deck should be as dry as possible before any stain is applied and the temperature should be within the range prescribed by the manufacturers. It is always advisable to use the same product for refinishing to ensure that the new coating is compatible with the old.
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