Deck repair: what to know

What the job involves, what changes the price, and what to ask a pro.

What deck repair is

Deck repair replaces rotted boards, loose railings, damaged stairs and weak framing or fasteners, then reseals the surface so the deck is sound again. Most decks fail first at the boards that stay wet, the ledger where the deck meets the house and the posts that sit in the ground, so a good repair checks those points first.

Signs you need it

  • Decking boards are soft, spongy or splitting, and a screwdriver sinks into the wood
  • The deck feels bouncy or sags in the middle, which can mean the joists or beams are weakened
  • The railing rocks, is loose at the post or has come away from the frame
  • Stair treads flex, creak or have cracked, and the stringers look damaged at the bottom
  • The deck has pulled away from the house or the ledger shows gaps, rot or rust on the bolts
  • Nails are popping up or fasteners are loose, and the boards are cupping or lifting

What the pro does

  • Inspect the deck from below and above, checking the ledger, the posts, the beams and the joists for rot and movement
  • Probe the wood with a screwdriver or an awl to find soft spots, and mark each one for replacement
  • Replace rotted boards with new decking of the same or a compatible material, spacing them for drainage
  • Sister or replace damaged joists and beams, and set new post bases or hardware where the old ones have failed
  • Reattach or rebuild the railings and stairs, using structural fasteners and the proper hardware for the load
  • Clean, sand and seal or stain the deck, and check the flashing and the fasteners before the finish goes on

What changes the price

Every job is different, so we do not publish prices. These are the things that move the quote up or down.

  • Number of boards to replace and how much of the deck framing is affected by rot
  • Whether the ledger and the house attachment must be rebuilt, which is more involved than a board swap
  • Post replacement, including whether the posts sit in concrete or are set on bases
  • Railing and stair repairs, such as new balusters, stringers or a full stair rebuild
  • Access to the underside of the deck, which can be tight on low decks or where the ground is steep
  • Finish type and the amount of cleaning and sanding needed before resealing

What a written quote should spell out

  • Boards, joists, beams and posts to be replaced, with the sizes and materials named
  • Ledger and flashing repairs, listed as a separate line if they are needed
  • Railing and stair repairs, with the fasteners and hardware used
  • Cleaning, sanding and the finish product named, with the number of coats
  • Permit needs, if the repair changes the structure or the stairs
  • Warranty on the workmanship and the boards, and what it does not cover

Questions to ask before you hire

  • Where is the rot coming from, and will you fix the cause as well as the boards?
  • Are the ledger and the posts sound, or do they need rebuilding?
  • Will you replace the rotted joists or only the boards on top?
  • What material are you using for the boards, and how will it match the old deck?
  • How will you attach the railings and stairs so they hold when someone leans on them?
  • Do you check the flashing at the house wall during the repair?

Red flags

  • Replaces the top boards over rotted joists and says the deck is fixed
  • Ignores a soft ledger or a loose attachment to the house
  • Reattaches a loose railing with the same short screws that failed
  • Says the deck can be sealed over rot without removing the damaged wood
  • Quotes a stair repair without looking at the stringers and the attachment at the top

What you can do yourself

A homeowner can replace a few surface boards on a low, sound deck, and can clean and reseal the surface. Call a pro for soft joists, a loose or rotted ledger, sagging beams, failed posts, loose railings or any stair that flexes, since those failures can drop people through the deck. Pressure-washing and sanding throw dust and debris, so wear eye protection, a dust mask and gloves, and keep children and pets away from the work.

Licenses and permits

Whether deck repair needs a contractor license varies by place, and structural repairs, ledger work and stair changes are commonly done under a contractor license in many areas. Check with your state or local licensing agency and your local building department before work starts, especially if the repair changes the attachment or the stairs.

Deck repair questions

Can a rotted deck be fixed, or does it need to be replaced?

Many decks can be repaired if the rot is limited to boards and a few joists, but widespread rot in the ledger, the beams or the posts usually means a rebuild. Ask the pro to probe the structure and tell you which parts are sound.

How do I know if the ledger is safe?

A ledger should be firmly attached with proper fasteners and flashing, with no gaps, rot or movement at the house wall. A pro should check it from below and the house side, since it is one of the most common failure points.

Will the new boards match the old ones?

New boards will look different until they weather, especially if the old deck was a different species or was stained. Ask the pro to match the color and the grain as closely as possible, and plan on refinishing the whole deck.

About this guide

This national guide is written and checked by infinibell. Rules and conditions differ by place, so local pros are credited on guides for the cities they serve, not on national ones.

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