Repair vs Replace Deck Cost
With decks the visible boards are almost never the real question. What matters is whether the bearers, joists and posts underneath are sound, because that is what you are actually paying to keep or replace.
Repair or resurface
- Typical cost
- Sand and re-oil $30 to $55 per m². Replace individual boards $90 to $160 each fitted. Full reboard over an existing frame $110 to $190 per m². Balustrade upgrade $180 to $350 per lineal metre. Add blocking to stop bounce $600 to $1,600.
- Expected remaining life
- Re-oiling buys one to two years of appearance. New boards on a sound frame buy 15 to 25 years in hardwood. The deck's real life is capped by the frame you kept.
- Disruption and downtime
- One to two days for sanding and oiling, with the deck out of use for another two to three days while the oil cures. Three to five days for a full reboard.
- Ongoing maintenance cost
- Hardwood needs re-oiling every 12 to 24 months at roughly $15 to $30 per m². Annual cleaning keeps the fixings and board ends dry and slows rot.
- Warranty
- Workmanship warranty usually 12 months to 6 years depending on state and contract value. Board and oil products carry their own manufacturer terms.
- When it is false economy
- Laying beautiful new boards over joists that are already soft, or oiling a deck where the post bases have rotted at ground level. You will pull it all up within a few years.
Rebuild the deck
- Typical cost
- Treated pine deck $180 to $280 per m². Hardwood deck $250 to $420 per m². Composite deck $280 to $480 per m². Add $2,000 to $6,000 for elevated decks needing engineered footings, stairs and compliant balustrades.
- Expected remaining life
- Hardwood on a well detailed frame 20 to 30 years. Treated pine 15 to 25. Composite boards 25 plus on a hardwood or steel frame. Footings and posts if detailed correctly can outlast all of them.
- Disruption and downtime
- One to three weeks including demolition, footings, curing time and finishing. The outdoor area is a construction site throughout and access to the back of the house is restricted.
- Ongoing maintenance cost
- Composite needs washing only. Hardwood still needs oiling. A rebuild is the moment to choose the maintenance regime you actually want for the next two decades.
- Warranty
- Structural work carries statutory warranty in most states for work above a threshold value, commonly six years. Composite boards often carry 15 to 25 year manufacturer warranties against splitting and rot.
- When it is false economy
- Demolishing a deck whose frame is fine because the boards look grey. A sand and oil for $1,200 would have solved the actual complaint.
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Pricing reviewed June 2026. Indicative Australian costs, not a quote.
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Understanding repair vs replace deck costs in Australia
The frame decides everything
A deck is two assets stacked on each other. The visible boards take the UV, the foot traffic and the spilled drinks, and they are the cheap half. Underneath sit the joists, bearers, posts and footings, which carry the load and which take three quarters of the labour to build. That is why the repair or rebuild question is really a question about the frame. If the frame is sound, replacing boards is a straightforward job at roughly $110 to $190 per square metre. If the frame is not sound, everything above it has to come off anyway, and you are into a rebuild at $250 to $420 per square metre in hardwood. Test the frame before you form an opinion about the deck.
The age threshold for Australian decks
Expected life depends heavily on detailing and exposure. A hardwood deck built with proper flashings where it meets the house, decent ventilation underneath, and posts on stirrups rather than buried in concrete should give 20 to 30 years. Treated pine typically gives 15 to 25. A deck that is fully exposed to weather with no eave protection ages faster, and one built low to damp ground with poor airflow can be finished in twelve. Rather than a fixed age threshold, use this rule. Under ten years, damage is almost always a detailing fault worth repairing. Ten to eighteen, inspect the frame carefully. Over eighteen with any substructure rot, rebuild.
Where decks actually rot
Rot is predictable and it shows up in four places. The base of posts, where timber meets soil or a slab and stays damp. The joist ends where they meet the house, especially where no flashing was installed and water tracks down the wall. The board ends, particularly cut ends that were never sealed. And anywhere two pieces of timber sit face to face and trap moisture without airflow. Notice that none of these are the middle of a board in open sun. If your damage is confined to surface greying and a few splintered boards, the deck is weathered, not failing. If it is concentrated at posts and joist ends, the deck is failing regardless of how good the boards look.
The repair cost rule of thumb
The 50 percent test works well here. Price the full rebuild for your deck size first, then see where the repair lands. On a thirty square metre hardwood deck a rebuild is roughly $7,500 to $12,600, so the halfway line is around $5,000. A reboard at $110 to $190 per square metre lands at $3,300 to $5,700, right on the line, which is why the frame condition is the tiebreaker. Sanding and oiling at $900 to $1,650 is comfortably worth doing at almost any age if the timber is sound. Post replacement, at $800 to $1,800 per post once you count the temporary propping, is what usually pushes the total past the line.
Compliance is part of the decision
Two requirements catch older decks. Where the deck surface is more than one metre above the ground, the National Construction Code requires a balustrade at least one metre high, with openings that will not pass a 125 millimetre sphere, and no horizontal climbable elements in the critical zone on decks above four metres. Many decks built before the 2010s fail one or both. Second, decks above certain heights and areas generally require council approval and, in some states, an engineered footing design. If you are rebuilding, this is handled as part of the build. If you are repairing an old non compliant deck, bringing the balustrade up to standard is money well spent, because it affects insurance and gets raised at sale.
Timber, composite and what each really costs to own
Hardwood decking in spotted gum, blackbutt, merbau or ironbark costs roughly $250 to $420 per square metre installed and looks superb, but it needs oiling every twelve to twenty four months at about $15 to $30 per square metre, or it silvers and eventually splinters. Treated pine is cheaper at $180 to $280 but is softer and dents. Composite runs $280 to $480 installed, does not need oiling, does not splinter, and carries manufacturer warranties commonly in the 15 to 25 year range, but it gets hot underfoot in dark colours and cannot be sanded back if it scratches. Over a fifteen year horizon, once maintenance is counted, hardwood and composite land closer than the sticker prices suggest.
When a repair only defers the rebuild
The pattern to avoid is spending real money on the surface of a deck whose frame is at the end of its life. New boards over soft joists look wonderful for two years, then the fixings start pulling and sections feel spongy, and the new boards get demolished along with the old frame. If a builder quotes a reboard without going underneath with a torch, get another quote. Equally, replacing three rotten boards every summer for four years costs more than a reboard and never solves the moisture problem causing it. Find the water source, fix the detailing, then decide on the timber.
Frequently asked questions
Is it worth repairing a 15 year old deck?
It depends entirely on the frame. If the posts, bearers and joists resist a screwdriver probe, then a reboard at roughly $110 to $190 per square metre or a sand and oil at $30 to $55 per square metre is excellent value on a fifteen year old deck. If the post bases or joist ends are soft, no surface work is worth doing, because the structure below has a few years left at best.
What warranty applies to deck work in Australia?
Structural building work above a state threshold value carries statutory warranty, commonly six years for structural defects and two years for non structural, and licensed builders must hold home warranty insurance above that threshold. Smaller repairs typically carry a contractor's own workmanship warranty of 12 months. Composite decking boards often carry separate manufacturer warranties of 15 to 25 years against rot and splitting.
How much does it cost to replace deck boards only?
Relaying new boards over a sound existing frame runs roughly $110 to $190 per square metre in hardwood, so a thirty square metre deck lands around $3,300 to $5,700. That assumes the joists are straight, correctly spaced for the board thickness, and do not need repair once the old boards come off, which is worth allowing a contingency for.
Can I sand and re-oil rather than replace the boards?
Usually yes, and it is the most under used option. Australian hardwoods weather to silver grey within two years without oil, which reads as failure but is only UV surface damage. A drum sand plus two coats of decking oil at $30 to $55 per square metre restores the colour and grain. It will not fix boards that are cupped enough to pond water, split through the fixings, or soft to a screwdriver.
Does my deck need council approval to rebuild?
In most Australian states a deck attached to a dwelling above a certain height, commonly around one metre, or above a certain floor area, requires either a complying development certificate or full development approval, and engineered footing details. Rules vary by state and council, so check before demolition. Replacing boards on an existing compliant frame is generally maintenance and does not need approval.
Is composite decking worth the extra cost?
It costs roughly $280 to $480 per square metre installed against $250 to $420 for hardwood, but it removes the oiling cycle entirely, which is $450 to $900 every year or two on a thirty square metre deck. Over fifteen years that maintenance saving typically outweighs the higher purchase price. The trade offs are heat underfoot in dark colours and the fact that scratches cannot be sanded out.
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