How do I inspect my own deck or balcony for rot before it becomes dangerous?

What you need

A flat-blade screwdriver or a scratch awl, a bright flashlight, a small hammer, painter's tape to mark findings, and your phone for photos. If the deck is more than a few feet up, a stepladder for the underside. Dry weather is better for seeing stains, but a day after rain shows you where water is still sitting, which is useful too.

Probe, do not just look

Paint and the weathered surface of wood hide a lot. Press the tool firmly into the wood at an angle. On sound lumber it will dent a sixteenth of an inch or so and stop. On decayed wood it sinks in with little effort, sometimes an inch or more, and pulls out fibers. Tap with the hammer too: solid wood rings, rotted or hollow wood thuds.

Probe at the bottom of each post, where the post meets the base or the concrete. Probe the ledger along its lower edge and at every bolt. Probe each joist end you can reach, especially the ones at the open edge of a balcony. Probe the base of every railing post where it passes the deck boards. Probe the feet of stair stringers where they meet the landing.

What to look for underneath

Water stains in a line below a joint usually mean a leak that has been there a while. Dark streaks down the wall under a ledger mean water is getting behind it. White or orange fungal growth is active decay. Mud tubes climbing a post or the foundation are subterranean termites. Rusted or weeping fasteners and hangers mean the hardware is wet and probably undersized for the exposure.

Also look at geometry. Does the deck slope away from the house, or has it started to sag toward the middle? Are the joist hangers fully nailed, or did someone use a few drywall screws? Is there any daylight between the ledger and the house?

• Staining or streaking on the wall below the ledger
• Fungal growth, mushrooms, or a musty smell
• Mud tubes, pellets, or shed wings
• Rusted hangers, missing nails, or corroded bolts
• Sag, lean, or a railing that moves when pushed

Test the railing and stairs

Lean on the railing at each post with a steady push. It should feel like part of the structure. Any give at the base means the post connection or the rim joist behind it is compromised. Walk the stairs and feel for bounce or treads that rock. Both are common places for rot because the wood meets concrete or is cut and left unsealed.

When to stop and call someone

Soft spots in decking or trim are a repair to schedule. Soft spots in a joist, beam, ledger, post, or stringer are a safety issue, and a second-story balcony with soft joist ends should not be used until it has been looked at. In North County, the balconies we see fail are rarely the newest or the oldest; they are the ones that were painted over a few times instead of being probed.

Levi scopes repairs by opening the structure where the probe says to, documenting what is sound and what is not, and writing it up with photos before any work begins. If your inspection turns up insect evidence, a licensed pest control company should inspect before any wood is rebuilt.

Related questions