Check the joist spacing first
Composite boards need closer support than many wood boards. Trex's joist spacing guide says joists for composite decking should generally be no more than 16 inches on center, 12 inches if the boards run diagonally, and usually 12 inches or less under stair treads. Some thicker wood boards can span 24 inches in specific applications.
That gap matters on older decks. If your joists are 24 inches apart and you switch to composite, Trex's fix is to add a new joist between each existing one. That is real framing work, and it belongs in the quote before you compare totals. Ask the contractor to measure the spacing at several spots and write it down.
Philadelphia's EZ permit standard for decks shows what the City expects on new decks: boards installed perpendicular to the joists, each board bearing on at least three joists (or blocking between them), and composite decking that meets the ASTM standard the sheet lists (ASTM 7032) and is installed per the manufacturer's instructions.
What upkeep each one really needs
For Trex's current lines (Transcend, Enhance and Select), its care and cleaning guide calls for soap and water or gentle pressure washing, with a fan tip and no more than 3,100 psi. Trex does not recommend sanding composite; it changes the surface and voids the warranty for any condition the sanding causes. Older composite generations have different instructions, so get the care sheet for the exact product you're quoting.
Wood needs its finish maintained. NADRA's Check Your Deck checklist says that when mildew shows up or the coating has worn away, clean the deck and apply a new waterproofing coating. There's no single schedule for every species and finish, so ask what coating is proposed and how you'll know it's time to redo it.
If you see a manufacturer's maintenance cost comparison, read the fine print. Trex's decking comparison bases its upkeep figures on a 12-by-16-foot deck and leaves out labor, so it isn't your break-even math if you'd pay someone to stain.
Heat on a sunny deck
Both materials get hot in direct sun. Trex's FAQ says darker colors feel hotter and that even its heat-mitigating boards get hot on sunny days, so extended skin contact should be avoided, especially for young children. If your deck gets afternoon sun, set samples of the actual colors out there and feel them before you choose.
Permits in Philadelphia and the suburbs
The City's building permit page says that if your property isn't on the Philadelphia Historic Register, you often don't need a permit for repairs that are regular maintenance, while major repairs that aren't regular maintenance do need one. Historic properties need Historical Commission approval. Once a job moves into the frame (new joists, posts, footings, the ledger or stairs), confirm the permit question with L&I before work starts. In Bucks and Montgomery County, ask your township or borough code office. Our guide on whether a deck repair needs a permit covers both.
What the quote should spell out
Trex's resurfacing steps start with checking joist spacing and framing condition, then getting any needed permits, then removing the old boards and inspecting again. Its cost factors page lists deck size, design, product line and the substructure. Ask for wood and composite priced on the same scope:
Removal and disposal of the old boards.
The exact board product, color and fastening method.
Any added joists or blocking, plus stair treads, fascia and trim.
A written price or process for rot or damage found once the boards come off.
For more on keeping a sound frame and replacing only the surface, see replacing deck boards without rebuilding the frame.
Look before you buy boards
New boards on a failing frame are wasted money. From a safe spot, look for sagging, loose rails, rusted fasteners and damp areas near the ledger, where the deck meets the house. NADRA notes that if a screwdriver sinks a quarter to a half inch into the wood easily, or the wood feels soft and spongy, decay may be present. Don't load-test a deck that looks unstable; keep people off it and have a deck builder or home inspector evaluate it. Our guide on when joists or posts need a professional inspection lists the warning signs, and you can browse more deck guides.