The surface sits on the same structure
Most of the composite vs wood deck debate is about the boards you walk on. The posts, beams and joists under them are pressure-treated lumber in nearly every residential deck, whatever the surface. So the parts that actually fail (a rotted ledger, a footing that heaved, a joist that was overspanned) are the same risks on a composite deck as on a wood one.
Choose the decking for how you want to live with it. Judge the builder on the framing.
A deck that bounces when someone walks across it has a framing problem. It usually means joists that are undersized for their span, spaced too far apart, or missing blocking, or a beam carried on too few posts. Stiffer boards will not fix it. Neither will more screws.
A sound frame feels solid underfoot from the first day, and the decking on top of it can be replaced more than once over the life of the structure without touching the posts, beams or footings.
All of these sit on the same pressure-treated frame.
| Decking | Upkeep | In full sun | Wear | Worth knowing |
|---|---|---|---|---|
| Pressure-treated pine | Clean and stain or seal every couple of years | Cooler than composite or PVC | Checks and splits as it dries; grays and splinters if not sealed | Fasteners must be hot-dip galvanized or stainless |
| Cedar | Weathers to silver gray if left unfinished | Cooler than composite or PVC | Soft; dents under furniture and dog claws | Naturally decay-resistant heartwood |
| Tropical hardwood (ipe) | Turns silver unless oiled regularly | Cooler than composite or PVC | Very hard and very durable | Heavy, slow to cut, pre-drilled at every fastener |
| Capped composite | Washing once or twice a year | Noticeably hotter than wood, darker colors more so | Can scratch; a deep scratch does not sand out | Some boards need joists closer than 16 inches |
| PVC | Washing once or twice a year | Noticeably hotter than wood, darker colors more so | Scratches more easily than composite | No wood at all; lighter; shrugs off moisture |
Wood decking: pine, cedar and tropical hardwood
Pressure-treated pine is the most common deck board in the country. It is strong and stable enough when kept sealed, but it checks and splits as it dries and weathers, and as a rule a horizontal surface in full sun needs cleaning and a fresh coat of stain or sealer every couple of years. Skip that and it grays, cracks and starts to splinter.
Fasteners must be rated for treated lumber, hot-dip galvanized or stainless, because the preservative corrodes plain steel.
Cedar is lighter, smells good and has naturally decay-resistant heartwood, but it is soft and dents under furniture and dog claws. Left unfinished it weathers to silver gray. Dense tropical hardwoods such as ipe are the opposite: very hard, very durable and heavy, slow to cut and pre-drilled at every fastener. They hold up for a long time but turn silver unless oiled regularly, which many owners choose not to bother with.
How a deck is built
Plan, permit and lay out
Draw the deck with joist sizes, spans and footing locations, get the permit, and mark utilities before digging.
Dig and pour footings
Dig each footing below frost depth, have it inspected where required, and pour concrete with post bases set in line.
Set the ledger or a freestanding beam
Bolt and flash a ledger to the house framing, or build a freestanding beam where the house cannot safely carry one.
Raise posts and beams
Set treated posts on the bases, cut them to height and carry the beams on them with proper connectors.
Hang joists and block them
Hang joists at the spacing the decking requires, crown up, with blocking and hangers fastened with rated hardware.
Lay decking and fasteners
Install boards with hidden fasteners or face screws, holding the end and side gaps the material calls for.
Stairs, railings and final inspection
Build stairs with even risers, fasten guards to resist the required loads, and call for the final inspection.
Composite, capped composite and PVC
Composite boards are a blend of wood fiber and plastic. Early uncapped versions faded, stained and grew mold because the wood fiber at the surface took on water. Most composite sold now is capped: a plastic shell wraps the core, which makes it far more resistant to fading, staining and moisture. PVC boards contain no wood at all, are lighter, and shrug off moisture entirely.
Composite and PVC get noticeably hotter than wood in direct sun, and darker colors more so; on a south or west exposure that matters for bare feet. Both can scratch, PVC more easily, and a deep scratch through the cap does not sand out the way wood does. Both expand and contract with temperature, so gaps at board ends follow the manufacturer’s figures rather than habit. The maintenance becomes washing, usually once or twice a year, instead of staining.
Shade, canopy and the north side of the house
Under the mature oak and maple canopy common on the Main Line, many decks sit in shade most of the day and dry slowly after rain. That is where mold and mildew grow, on wood and on composite alike. Capped boards resist it better than uncapped ones, but pollen, leaf litter and tannins still sit on the surface and feed growth if they are not washed off.
A shaded deck on the north side of a house needs gaps kept clear between boards so water drains and air moves, and it needs a spring and fall cleaning whatever it is built from. Leaves left on a deck through the winter stain wood and composite both.
What the framing has to get right
Footings go below frost depth so freezing soil cannot lift them. In this part of southeastern Pennsylvania the requirement is typically 30 to 36 inches depending on the municipality, so check with the township, which sets the requirement and inspects the holes before concrete is poured.
Posts sit on the footings in metal bases, not buried in soil to rot. Clay soil that holds water and freezes hard is exactly what lifts a shallow footing, a little each winter, until a corner of the deck is out of level and the stair no longer lines up.
Where a deck attaches to the house, the ledger board is fastened with through-bolts or structural screws into the house framing, never nails, and flashed so water cannot get behind it. A poorly fastened or rotting ledger is the most common cause of serious deck failures. On older stone houses a ledger often cannot be attached safely to the masonry, and a freestanding deck carried on its own beam and footings beside the house is the better design.
Joists are typically 16 inches on center for wood and most composite decking; some composite and PVC boards, and nearly any board run on a diagonal, need closer spacing, often 12 inches. The board maker’s span rating decides it.
Hidden fasteners clip into the board edges, leave the surface clean, and set the gap between boards consistently. Every connector in the frame, from joist hangers to post bases, should be a rated metal connector fastened with the nails or screws its maker specifies, not deck screws driven wherever they reach.
Permits and when to do it yourself
Most townships require a building permit for a new deck, especially one attached to the house or raised above grade, with inspections at the footings, the framing and the finish. Check with the township or borough before anything is ordered.
Replacing worn deck boards on a sound frame is a reasonable project for a careful homeowner. Building a new frame, setting footings or attaching a ledger to a house is structural work, and it is the part that has to be right.
Before resurfacing an old deck, probe the ledger, the joist ends and the posts near grade with a screwdriver. Soft wood there means the frame needs work first, and new boards on a failing frame are money spent twice.