How to Repair a Leaning Wooden Deck

Locate the problem. Inspect the structure of the deck to see what is causing it to lean. It could be broken post or beam or it could be a sinking foundation. Make sure that the rest of the deck structure is sound before attempting a repair. If the deck is badly damaged, consider replacing it, or having it replaced, instead.

Level the deck. Use a jack to raise the low parts of the deck so that it is level. Add temporary supports to hold the deck in place while you work. These can be made by attaching 2x4s between the deck beams and posts driven in the ground. Be sure the posts will not sink under the weight of the deck, and that the supports will not interfere with your repair work.

Repair the foundation, if necessary. If the leaning deck is caused by a sinking foundation, be sure the soil underneath is well-compacted to prevent future settling. Add fill dirt or pour concrete piers if necessary to build a strong foundation.

Remove any damaged lumber. A reciprocating saw is useful for cutting away the old boards.

Replace the wood you removed with similar but new lumber. Check to see that the deck is "even" by using your level, and securely attach the new boards using weather-resistant screws or nails.

Remove the temporary supports. As the supports are removed, be sure that the repairs are able to hold the weight of the deck.