Check several different areas of the deck to be sure the wood is still sound. This includes the ledger board (where the deck attaches to the house and a common source of deck failure), support posts and joists under the deck (if you can reach them), deck boards, railings and stairs.

Pay special attention to any areas that tend to remain damp, are regularly exposed to water, or are in contact with fasteners. Use a tool like an ice pick or a screwdriver to penetrate the wood surface. If you can easily penetrate ¼ to ½ inch, break off a sliver of wood without splinters, or the wood is soft and spongy, decay may be present. This is also a good time to look for small holes in the wood, which may indicate insects.

üFlashing:

Flashing is a metal or plastic guard that directs water out and away from sensitive areas. It’s often installed where the deck and house come together, keeping moisture and debris from collecting between the house and the deck’s ledger board. Be certain the flashing is sound and firmly in place. Consider adding or replacing flashing if you notice areas that are obviously allowing water to collect.

Fasteners include nails, screws or anchors in the ledger board. Tighten any loose fasteners and pound in any nails that have popped up. (Note: The ledger board should not be fastened with only nails.) If a fastener appears rusted or corroded, consider replacing it. A corroded fastener can cause  deterioration in surrounding wood. The deck or stairs should appear even without sagging and should not sway or move when tested.

üRailings and Banisters:

These should be secure. Push on them to be sure there is no give. Also, check to be sure they are high enough (most codes require a 36″ high railing and usually encourage 42″ high railings) with rails no more than 4″ inches apart (measured from the inside of the rails) to keep small children and pets from squeezing through. This is especially important the higher your deck is off the ground.

üStairs:

Check any railings (guardrails) or handrails to be sure they are firmly held in place; check also the risers (vertical portion) and stringers (horizontal portion) to be certain they are securely attached and not decayed. Look for splits at the edge of the treads. If the area behind the stair treads is open, this opening should be no more than 4″ high to prevent a danger for small children. Also, always keep stair pathways clear of planters, décor, toys and other items that can present a tripping hazard.

üCleaning and Maintenance:

Clean away any leaves and debris, since these can be slippery and promote mildew. If mildew is present or the deck coating has worn away, make time to clean and apply a new waterproofing coating. It can help prevent the split, decayed wood and loosened fasteners mentioned earlier.

üGrills, Fire Pits and Chimneys:

These features can create a warm and cozy deck atmosphere, but make sure any source of fire or heat is safely placed away from flammable surfaces or that the deck surface is protected by a non-flammable pad. Always use caution and follow manufacturers’ directions.

üLighting and Electrical:

Be sure all lighting is working; clean any light covers to allow maximum light to shine through, and trim any plants or tree limbs that may be blocking light.

If you don’t have adequate lighting, there are a lot of great new deck lighting products you could consider to illuminate your steps and pathways.

Be sure all electrical outlets, appliances and features are up to code, in good condition, and childproof if children are present. Watch that any electrical cords do not present a
tripping hazard.

üOutdoor Furniture and Storage:

Test all outdoor furniture to be sure it is sturdy. Avoid placing seating right at the edge of the deck. If you have a swing or hammock installed, test the chains and ropes to be sure they are secure. Consider installing childproof latches on any storage boxes and benches.

Be sure to keep all deck related chemical products stored safely away from children, including BBQ lighter fluids, matches, cleaners, etc.

üSurroundung Trees:

If you have trees overhanging your deck, make certain there is no danger of decaying limbs breaking free and falling from trees surrounding the deck.

Source: http://nadra.org/DSM_checklist2008.pdf