I get called out to decks that look fine all the time. The boards are solid underfoot. The railing doesn’t wobble. The stain is holding. Everything visible from above says the deck is in good shape.
Then I get under it with a screwdriver. The ledger board (the board that connects the deck to the house) has been slowly rotting for years where it meets the house frame. The joist ends out at the beam are soft enough to push a finger into. Two joist hangers, the metal brackets that hold the joists to the ledger, have pulled away from a ledger that can’t hold them anymore.
The deck that looked fine from the top isn’t safe. It was still standing because decks are built with extra strength to spare, and the rot hadn’t gone far enough yet to make it visibly sag. It won’t hold forever.
Deck joist rot like this is the most common structural problem I find on Colorado Springs decks over 15 years old (and I’ve crawled under a lot of them). It’s also the easiest to avoid. Check the parts you can’t see from the surface once a year.
Why Colorado Springs Accelerates Deck Rot
Rot needs two things: moisture and wood, and I hear all the time from homeowners who assume our dry air keeps them safe from it. Colorado’s dry air makes you think rot is less of a problem here than in wet parts of the country. In some ways it is. Deck surfaces and the framing above the ground do stay drier here than in the Pacific Northwest or the Southeast. But the exact spots where deck rot starts are the spots where water collects and stays, no matter how dry the air is.
The ledger connection traps water. The ledger board is bolted or screwed tight against the house band joist (the board that runs around the edge of the house floor frame), pressing two pieces of wood together. Water gets between them from rain running down the siding, from snowmelt sitting against the ledger, and from condensation. Then it stays there. The two tight wood faces keep it from drying out. In Colorado Springs, that trapped water goes through more than 100 freeze-thaw cycles a year. Each time it freezes it expands and stresses the wood fibers, breaking down the wood and opening the door for rot fungus. Every rotten ledger I’ve pulled off a house started exactly this way (and most of them had little or no flashing behind the siding).
Cut ends soak up water fast. Wood is made of tiny tubes that run along the grain, like a bundle of straws. A cut end, called end grain, leaves those tubes open to the air. Wood pulls in water through end grain about 15 to 20 times faster than through its flat faces. Every joist end at the beam, every ledger end, and every post bottom sitting on a footing is one of these thirsty, high-risk spots. When that water freezes and expands, it slowly breaks the wood fibers apart.
Joist hangers hold water against the wood. A joist hanger is the metal bracket that ties each joist to the ledger. Metal pressed into wood keeps a thin film of water trapped where the two meet. Over the years, that makes a constantly damp spot at every hanger, which is exactly where the joist connects to the ledger and carries its load.
Missing flashing is the main cause of ledger rot. Flashing is a metal or membrane strip that channels water away from the seam where the ledger meets the house. Good ledger flashing keeps water out of the most vulnerable spot on the whole deck. Many older Colorado Springs decks have poor flashing or none at all. The building code (the IRC, which Pikes Peak Regional Building uses) added strong ledger connection rules in its 2009 edition and a clear deck ledger flashing requirement in 2015. But older decks were built and approved under earlier codes, and an inspection of an existing deck does not usually force it to be brought up to today’s code.
The Inspection: Where to Look and What to Look For
Get under the deck. I can’t judge structural rot from the top of a deck, and neither can you, no matter how good it looks. You have to look at the underside: the face of the ledger, the tops and bottoms of the joists, the joist ends at the beam, the spots where the beam sits on the posts, and the bottoms of the posts.
The screwdriver test. I carry a flathead screwdriver on every deck inspection, no exceptions, and press it firmly into the wood at every important connection. Sound pressure-treated lumber pushes back. It takes real force just to dent it. Rotted wood is soft and stringy. The screwdriver sinks in with almost no effort, and the wood feels spongy and mushy.
Inspect in this sequence:
Ledger board: Look at the face of the ledger, the board fastened to the house. Check the flashing at the top of the ledger where it meets the siding. Look for water stains, dark discoloration, or any gap opening up between the ledger and the house. Probe the face and, especially, the ends of the ledger with the screwdriver. Probe the top edge too, where water sits.
If you can, check the house band joist behind the ledger from inside the basement or crawlspace. The rot often starts where the ledger meets that band joist and works into it before you can see anything from outside.
Joist ends at the beam: Move to the far end of the deck, away from the house, where the joists rest on the beam. These joist ends are the second most common place to find rot. Probe each one. Probe the face of the beam too, and the spots where the beam sits on the posts.
Joist hangers: Check that every hanger is firmly nailed with the right fasteners. Hangers need joist hanger nails, not drywall screws, which are not rated to hold structural loads and can snap. Worry about any hanger that has pulled away from the ledger, or any spot where the ledger wood behind a hanger feels soft.
Joist tops: From below, look at the top edge of each joist, where water sits after rain. Dark staining along the top means water has been collecting there for a long time. Probe any stained sections.
Post bases: Check where each post meets its footing. Posts should sit on standoff bases, metal brackets that hold the post up off the concrete footing instead of buried in it. Posts set into concrete rot right where they meet the concrete. A post on a standoff base can be probed above the ground. A post buried in concrete has to be probed down at the soil line.
What the Findings Mean
Sound wood everywhere: Good news, that’s the call I like to make. Keep inspecting once a year, add flashing if it is missing, and carry on.
Soft joist ends (rot within 12 inches of the end): A sister repair may work, and it’s the fix I end up doing most often on these calls. That means bolting a sound, full-length joist alongside the damaged one and tying it into the ledger the right way. The rotted end gets cut back to solid wood, and the new sister joist carries the load at that spot. This is a repair, not a full replacement.
Soft joist ends (rot more than 12 inches into the joist): The whole joist has to be replaced. It comes out and a new one goes in. The deck boards above have to be held up with temporary supports while that joist is swapped out.
Soft ledger: This is the most serious finding, and it needs attention right away. You cannot just sister a bad ledger. The bolts or structural screws that run through the ledger into the house have to bite into solid wood, and rotted wood will not hold them. Replacing the ledger means pulling the deck boards near the house, removing the old ledger, checking and repairing the house band joist behind it, installing a new pressure-treated ledger with the right structural fasteners, and putting in correct flashing before the deck boards go back down.
Soft posts or beams: This is a major structural repair. Posts and beams carry the main weight of the deck. Rotted posts or beams have to be held up with temporary supports while new ones go in.
The Failure Mode: Why It Matters
Most deck failures aren’t slow, visible events, which is exactly why I don’t trust a deck just because it looks fine. The deck acts normal and shows no sag, and then it gives way all at once under load. That often happens during a party, when the deck is holding far more weight than usual.
The numbers are sobering. About 6,500 Americans a year are hurt when a deck or porch structure fails, according to Consumer Product Safety Commission data. Injuries peak in summer, when decks get the most use and gatherings pile on the most weight. Ledger failures, the most common kind of deck collapse, drop the deck away from the house suddenly, with almost no warning.
This is not meant to scare you. Most decks are sound and will stay that way with basic upkeep. The point is simple. Checking a deck for real is not the same as looking at it from above and deciding it looks fine. A real check means getting underneath, probing the key connections with a tool, and being honest about what you find.
What Proper Repair Costs in Colorado Springs
Sister joists (isolated joist end rot): $150–$400 per joist for materials and labor, depending on how easy the spot is to reach and the joist size.
Full joist replacement: $200–$500 per joist, including temporary deck support and reinstallation.
Ledger replacement (including proper flashing): $1,500–$3,500 depending on deck size, ledger length, and whether the house band joist behind it needs repair.
Post replacement: $300–$800 per post, including temporary supports.
Full structural assessment: Included in the estimate walkthrough. You should not pay for the assessment separately.
Fixing joist rot before it reaches the ledger costs far less than fixing a rotted ledger. Fixing a rotted ledger costs far less than rebuilding a deck after it collapses. A yearly inspection costs nothing, and it’s the cheapest insurance I know of.
Inspect this spring. That screwdriver test tells you everything you need to know, and it only takes about ten minutes.
For a free structural assessment of your Colorado Springs deck, call (719) 243-9718.
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