The Ledger Board: Where Most Failures Begin
The ledger board is the horizontal piece of lumber bolted to the house that supports one side of the deck. It carries half the deck's weight plus whatever's on it. People, furniture, that grill, the hot tub someone added without checking if the structure could handle it.
According to a study by the North American Deck and Railing Association, ledger connection failure is the leading cause of deck collapses. Not rotten boards. Not failed railings. The connection to the house.
What I Check
First, I want to see lag bolts or through-bolts every 16 inches, staggered top and bottom. Not nails. Not screws. Bolts. The bolt heads should be visible, and there should be a lot of them.
Second, I look at the flashing above the ledger. Water running down the house needs to be directed over the ledger, not behind it. Missing or improper flashing means water gets trapped between the ledger and the house, rotting both from the inside out.
Third, I probe the ledger with an awl. If the tool sinks into soft wood, the rot has started regardless of what the surface looks like.
The Nailed Ledger Problem
Decks built before the late 1990s were often attached with nails alone. Building codes didn't require bolts until relatively recently. Those nails pull out over time as the deck moves with temperature changes and loading cycles.
If I find a nailed ledger, it goes in the report as a safety concern requiring immediate attention. The fix isn't complicated: add lag bolts through the existing ledger into the rim joist or house framing. Cost for a typical 16-foot ledger: $200-400 in materials and a few hours of work.
Posts and Footings
The posts hold everything up. Fail here and the whole structure comes down.
Ground Contact Rot
Even pressure-treated lumber rots when it sits in perpetual moisture. Posts that contact the ground directly, without standing on concrete piers, absorb water from below. The rot starts inside, where you can't see it, and works outward.
I carry an awl specifically for probing post bases. Push it into the wood about 6 inches up from the ground. Healthy wood resists. Rotten wood lets the tool sink in. I find hidden rot in about 30% of decks over 15 years old.
My colleague Sandra found a deck last summer where the posts looked fine visually but were hollowed out from rot. She pushed on one and her hand went through it. The entire deck was being held up by the decking and rim joist, not the posts. How it hadn't collapsed already was a mystery.
Inadequate Footings
Posts need to rest on concrete footings that extend below the frost line. In much of the northern US, that's 36-48 inches deep. Footings that don't go deep enough heave with frost cycles, pushing the deck up and creating structural stress.
I can't see underground footings during a normal inspection. But I can look for symptoms: posts that aren't plumb, deck surfaces that aren't level, gaps opening between the deck and house. These suggest footing movement.
Notched Posts
Older construction methods often notched the top of the post to accept the beam. Modern codes prohibit this because the notch removes wood from the strongest part of the post and creates a failure point.
When I find notched posts, I recommend adding post-to-beam connectors that transfer load properly. The retrofit costs $20-40 per post in hardware and an hour or two of work.
Railings and Balusters
Railings prevent people from falling off the deck. You'd think this would make them high priority during construction. In practice, railings are one of the sloppiest parts of most decks.
Height Requirements
Current code requires 36-inch minimum railing height for residential decks, measured from the deck surface to the top of the rail. Many jurisdictions now require 42 inches. Decks built decades ago might have 30-inch railings or even lower.
I measure every railing. Below 36 inches gets noted as a safety concern. I also check that railings are present everywhere the deck is more than 30 inches above grade.
Baluster Spacing
A 4-inch sphere shouldn't be able to pass through any opening in the railing. This prevents small children from getting their heads stuck or slipping through. Older decks commonly have 6-inch or wider baluster spacing.
The 4-inch rule also applies between the bottom rail and the deck surface, and between balusters and posts. Every gap, every opening, everywhere.
Structural Integrity
I push on railings. Not politely, not gently. I grab the top rail and try to make it move. A proper railing feels solid. A failing railing flexes, wobbles, or feels like it might pull away from the posts.
Loose railings are common. Screws loosen. Wood shrinks. Connections that felt solid 10 years ago now have play. Sometimes tightening fasteners fixes it. Sometimes the connections need to be redone entirely.
Stairs
Deck stairs are where injuries happen. Falls, trips, missteps. When stair construction is wrong, it's not just a code issue. It's a safety hazard people encounter every time they use the deck.
Rise and Run Consistency
Every step should be the same height (rise) and depth (run). Humans learn the stair rhythm after the first step and expect consistency. A stair that's half an inch off throws off your stride and causes stumbles.
I measure rise and run on every flight of deck stairs. Variation of more than 3/8 inch between steps is a defect. I find inconsistent stairs on about 25% of the decks I inspect.
Stair Stringers
The stringers are the angled boards that support the stairs. They take significant load, especially when multiple people use the stairs at once. Stringers should be at least 2x12 lumber, properly cut so that at least 5 inches of solid wood remains at the thinnest point.
I probe stair stringers where they contact the ground, same as posts. Same rot problems, same hidden damage.
Handrails
Stairs with more than two risers need a graspable handrail. Not just a top rail, but something you can actually wrap your hand around. The standard 2x4 or 2x6 cap rail that matches the deck railing doesn't count unless there's an additional graspable rail below it.
Most deck stairs I see either have no handrail or have a cap rail that's too wide to grip properly. This is one of the most commonly missed code requirements.
Decking and Fasteners
The decking surface itself is actually the least critical structural component. Board failures are obvious and usually don't cause catastrophic collapse. But bad decking makes the deck unpleasant to use and can indicate deeper problems.
Board Condition
I look for split, cracked, or rotting boards. Cupped or warped boards that create trip hazards. Loose boards that move when you step on them. Surface checking (small cracks) is normal weathering on wood decks and doesn't usually indicate structural problems.
Fastener Issues
Popped nail heads, missing screws, and rusted fasteners all indicate age and potential problems. On wood decks, I want to see two fasteners per board at each joist. Missing or loose fasteners mean boards can shift and potentially become tripping hazards.
On older decks, I sometimes find completely wrong fasteners. Regular steel nails instead of galvanized or stainless. Drywall screws instead of deck screws. These fasteners corrode and fail faster than they should.
Joist Condition Below
From underneath the deck, I check joist spacing, hanger installation, and wood condition. Joists should be 16 inches on center maximum for most decking. Hangers should connect joists to the ledger and beams. Wood should be solid, not punky or showing decay.
The underside tells the real story. Whatever the deck surface looks like, the framing underneath determines whether it's safe.
What Repairs Actually Cost
Deck repair costs range widely depending on what's wrong and how accessible the problem is.
Simple Fixes
Adding lag bolts to a nailed ledger: $200-400. Replacing a few rotted decking boards: $50-200. Tightening loose railings and adding hardware: $100-300. These are DIY-friendly for handy homeowners.
Moderate Repairs
Replacing rotted posts: $300-800 per post including new footings. Rebuilding stairs to code: $500-1,500. Bringing railings up to current height and spacing requirements: $1,000-3,000 depending on deck size.
Major Work
Replacing the ledger board properly, including flashing: $1,500-3,500. Rebuilding the substructure while keeping existing decking: $3,000-8,000. Complete deck replacement: $15,000-30,000+ for typical suburban deck sizes.
The Decision Point
When a deck has multiple issues, homeowners face a decision: repair or replace? Here's how I think about it.
If the framing is sound and the issues are surface-level (decking, railings, cosmetics), repair makes sense. You're working with a solid foundation.
If the framing has rot, the ledger connection is questionable, and the footings are inadequate, replacement is often more practical. Fixing multiple structural issues on an old deck can cost nearly as much as building new, and you end up with a patched-together result instead of a properly designed structure.
I tell buyers: get the structural stuff right, even if it means living with worn decking for a few years. A structurally sound deck that looks tired is fine. A pretty deck that's going to pull away from the house is not.