Why deck maintenance matters
A well-built deck lasts decades, but the boards need some looking after to stay good-looking and safe underfoot. In the Manawatū, the main enemies are moss and mildew in winter, sun in summer, and leaf litter all year. This guide covers deck cleaning and oiling for timber decks, and care for composite decking.
We build new decks rather than maintain them, but these are the steps we would follow on our own decks.
How to clean a deck
- Clear it. Move furniture and pot plants, and sweep off leaves and dirt, including between the boards.
- Wash it. Use a deck cleaner made for your timber, applied with a stiff broom. For moss and mildew, a product designed to kill it works better than scrubbing alone.
- Rinse. Rinse thoroughly with a hose. Be careful with water blasters: up close they tear up the surface of softwood and leave it furry and more absorbent.
- Let it dry. Give it a couple of dry days before oiling or staining.
How to oil a deck
Choosing a deck oil
Deck oils come in penetrating oils that soak in and pigmented oils that add colour and UV protection. Water-based products are easier to clean up and dry faster; solvent-based oils often penetrate deeper. The best deck oil in NZ for your deck is one made for your timber and exposure. Pigmented oils last longer in full sun.
Oiling a deck, step by step
- Clean and dry the deck as above.
- Stir the oil well and test it on an offcut or a hidden corner.
- Apply thin, even coats along the length of two or three boards at a time, so you keep a wet edge.
- Wipe off any excess that has not soaked in, so it does not go sticky.
- Leave it to dry for the time on the tin before walking on it or putting furniture back.
Oiling a kwila deck
New kwila bleeds tannin, so wash it down several times over the first weeks before the first oil. After that, a yearly clean and oil keeps the colour. If you prefer silver-grey, you can leave it unoiled.
Restaining a deck
Treated pine decks are usually stained. To restain a deck, clean it, let it dry and recoat with the same type of product. If you are changing from an oil to a paint-type stain, or the old coating is peeling, it may need sanding back first.
Cleaning composite decking
Composite does not need oiling or staining. Wash it a couple of times a year with warm soapy water and a soft brush, rinse well, and clear leaves from shady corners so mildew does not get started. Avoid harsh solvents, and do not use a water blaster up close. See composite vs timber decking.
A simple yearly deck maintenance routine
- Autumn: sweep and clear leaves; treat moss and mildew before winter
- Spring: wash the deck; check for loose boards, raised screws and wobbly balustrades
- Early summer: oil or stain timber decks once dry
- Any time: keep gaps between boards clear so water drains
If your deck is soft underfoot, the boards are rotting, or the frame is failing, more oil will not fix it. Read when to replace a deck.