Deck maintenance: schedule, lifespan and costs
Updated
Overview
A deck is a wood or composite floor on a frame of joists, held to the house by a ledger board and up off the ground by posts. The boards you walk on get the attention, but the frame underneath is what decides whether the deck is safe, and it's the part nobody looks at. The maintenance is a cleaning every year, which is also the inspection, and a coat of stain or sealer on wood every year or few, so water stays out of the boards and the frame stays dry.
Lifespan
A deck lasts 15 to 30 years. Treated wood is at the short end, 15 to 25 years, and composite at the long end, 25 to 30. What shortens a wood deck's life is water: it soaks into unsealed boards, opens the grain, feeds mildew and rot, and works into the joints and the ends of the joists where it can't dry. A ledger board that isn't flashed properly rots behind the siding and takes the whole deck's support with it. Composite doesn't rot, but its frame is usually wood, and that frame can.
What extends the life is a sealer that keeps water on the surface, a yearly cleaning that strips the mildew, hardware tightened as it loosens, and a frame that's looked at. The signs a deck is near the end: boards that are soft or splintered across whole areas, joists that give when pressed with a screwdriver, a ledger board pulling away from the house, posts rotting at the ground, and railings that wobble no matter how they're tightened.
Maintenance schedule
The one scheduled job, which includes the cleaning that doubles as the inspection.
| Task | How often |
|---|---|
| Clean and reseal the deck | clean once a year, reseal every 1 to 3 years |
Alongside it, look under the deck once a year with a flashlight: press a screwdriver into the joists and the ledger board, and check that the post bases and the hardware are sound.
Replacement cost
Replacing a deck costs $4,000 to $15,000. The range depends on the size, the height off the ground, the material, and whether the frame can be reused. A simple ground-level treated wood deck is at the low end, and a large, raised composite deck with railings and stairs is at the high end. Composite costs more to build and less to keep.
The repair-or-replace rule: a few soft boards, a loose railing, a popped nail or a rotten post are repairs, and boards can be replaced one at a time. A frame that's rotten in several places, a ledger board that's failed, or a deck past the middle of its lifespan with soft wood through the structure is a rebuild, and often the posts and the footings can stay.
Common problems
- Boards that have gone gray and let water soak in: the sealer has worn off. Clean and reseal the deck.
- Green or black growth on the boards, slippery when wet: mildew. The yearly cleaning strips it, and sealing slows its return.
- Splinters and raised grain: sun and water have opened the wood. Sand the worst spots and seal.
- Loose boards and popped nails: the wood has shrunk around the fasteners. Drive screws beside the old nails.
- A railing that wobbles: loose bolts at the posts, or posts rotting where they meet the deck. Tighten first, and replace any post that's soft.
- The deck pulling away from the house, or a gap at the ledger: the ledger board's fasteners or flashing have failed. Keep people off the deck and have a contractor look at it.
FAQ
How long does a deck last?
Treated wood lasts 15 to 25 years and composite 25 to 30. Sealing wood on schedule and keeping the frame dry are what get it there.
How much does it cost to replace a deck?
$4,000 to $15,000, depending on the size, the height, the material and whether the frame can be reused.
How often should a deck be sealed?
Every 1 to 3 years for wood, with a cleaning every year. Sprinkle water on the boards: if it soaks in instead of beading, it's time.
Does a composite deck need maintenance?
A cleaning once a year, and a look at the wood frame underneath. It doesn't need sealing.
How do I know if my deck is safe?
Press a screwdriver into the joists, the ledger board and the posts. Sound wood resists. Soft wood, a ledger pulling from the house, or a railing that won't tighten means a contractor should look before anyone gathers on it.