Symptom → likely fix
| What you see | Likely cause | Typical fix |
|---|---|---|
| Soft or spongy boards | Rot in the board, or in the joist under it | Replace boards; probe and sister or replace the joist if it's soft |
| Wobbly railing or post | Loose or corroded fasteners, rot at the post base | Re-anchor with proper hardware or replace the post and guard section |
| Rotted posts | Posts set in soil or on wet concrete | Shore the deck, replace posts on raised post bases and sound footings |
| Failing stairs | Rotted stringers or treads, loose connections | New stringers, treads and handrail; check the landing |
| Water stains on the wall below the deck, or a soft ledger | Missing or failed ledger flashing | Remove boards at the house, repair or replace the ledger, flash it correctly |
| Sagging or bouncy deck | Undersized or rotted beam/joists, settling footings | Add or replace beams, joists or footings; may need a permit |
Where the parts are: most structural repairs happen at the ledger, joist ends, beam and post bases.
When repair stops making sense
Repair is worth it when the problem is local. When rot shows up in the ledger and several joists, footings have shifted, or the guards and stairs would all need rebuilding to meet current rules, a full rebuild usually costs less over time than chasing failures. That's the point to look at deck replacement.
What repairs cost
Angi puts the average deck repair at about $2,246 (Angi). Small board swaps cost much less; structural and ledger work costs more. See the deck cost guide for replacement and new-build numbers.
Who should do it
Structural deck repairs belong with a licensed contractor. Unless a job is under $1,000 in labor and materials, needs no permit and the worker has no employees, California requires a CSLB license (CSLB, AB 2622). Repairs to posts, beams or ledgers may need a permit. How to vet a deck builder.