You probably think your deck is fine. It looks good from the back door, the railings are still tight, and you walked on it yesterday without anything feeling wrong. But here is the uncomfortable truth about deck rot in Cary, IL: by the time you see it, it has already been working silently for 12 to 18 months, and the repair bill has likely tripled. That small soft spot near the ledger board or the slightly peeling stain on the corner post is not a cosmetic issue. It is a structural one. The average homeowner in McHenry County who catches rot early spends $300 to $800 on localized repairs. The homeowner who waits until a board breaks or the deck feels spongy is looking at $3,500 to $7,000 for a partial rebuild. This guide for 2026 shows you exactly what to look for, how to check it yourself, and when to call a professional like Burns Carpentry before the damage gets worse.
Why Early Rot Detection Saves You Money on Deck Repairs
Wood rot is not like a leaky faucet where you can see the drip. It starts where you cannot see it. The most common entry points in Cary decks are the spots where the deck frame meets the house, the tops of posts where water pools, and the ends of boards that touch the ground. By the time the wood feels soft or looks discolored on the surface, the fungus has already eaten through the outer layer and is working into the core of the board.
The cost math is simple. A single rotted joist end that gets caught early costs about $150 to $250 to replace, including the carpenter’s time and materials. Let that same rot spread to the ledger board, and you are now replacing a structural connection that holds the entire deck to your house. That repair runs $800 to $1,500 and requires temporary bracing. Let it go further and rot the rim joist, the band board, and the adjacent floor joists, and you are looking at a $4,000 to $6,000 repair that involves tearing off decking boards and rebuilding the frame.
In Cary’s climate, where we get freeze-thaw cycles from November through March and humid summers that keep wood damp, rot accelerates faster than in drier regions. A small pocket of rot that starts in late spring 2026 can compromise a full section of decking by the following winter. The key is catching it before the freeze-thaw cycle widens cracks and lets in more moisture.
4 Key Signs of Deck Rot Most Cary Homeowners Miss
Most people look for the obvious stuff: a board that crumbles when you poke it, visible mushrooms growing on the wood, or a railing that wobbles. Those are late-stage signs. The early indicators are subtler and often ignored because they look like normal wear. Here are the four that matter most in our area.
1. Peeling or bubbling paint or stain in isolated spots. If your deck has a single patch of peeling finish near a fastener, a post base, or a joint, that is not a paint failure. That is moisture pushing the finish off from behind. The wood underneath is almost certainly wet and beginning to decay. In Cary, this shows up most often on south-facing decks where afternoon sun heats the surface but the bottom stays shaded and damp.
2. Discoloration that follows a specific pattern. Normal weathering turns wood gray evenly across the surface. Rot discoloration looks different. It appears as dark, almost black streaks that follow the grain or spread in a blotchy pattern around a nail or screw head. If you see a dark ring around a fastener, that fastener is holding moisture against the wood and rot has already started in that spot.
3. A slight springiness or bounce in one section of the decking. If you walk across your deck and one board feels softer than the rest, or if the entire section near the house has a slight give, that is not a design flaw. The joist or support beam below that board has lost structural integrity. The wood fibers are breaking down. This is the most common early sign that homeowners in Cary miss because they attribute it to the deck getting older, but older decks do not get bouncy. Rotten decks do.
4. A musty, damp smell in the crawlspace or under the deck. This is the one you cannot see at all. If you have a deck with a low clearance and you smell wet earth or mildew when you walk near it, moisture is trapped underneath. That trapped moisture is rotting the underside of the decking and the frame. In Cary, decks built less than 18 inches off the ground are especially prone to this because airflow is restricted.
How to Inspect Your Deck for Rot: A Step-by-Step DIY Check
You do not need special tools for a basic rot inspection. A flathead screwdriver, a flashlight, and a pair of gloves are enough. Set aside 30 to 45 minutes on a dry day. Here is the process Burns Carpentry uses when we evaluate a deck for potential repairs.
- Start at the house connection. Walk the entire length where the deck ledger board attaches to your home. Look for gaps between the ledger and the siding, rusted flashing, or any place where water can run behind the board. Push the screwdriver tip into the ledger board at 12-inch intervals. If it sinks in more than an eighth of an inch, you have rot in the structural connection.
- Check every post base. Kneel down and look at the bottom of every support post where it meets the concrete footing or ground. Water splashes up from rain and snow melt, and this is where rot starts on posts. Prod the bottom 2 inches of each post with the screwdriver. If the wood feels soft or crumbles, that post needs replacement.
- Inspect all fastener heads. Walk the deck and look at every screw, nail, and bolt head. If you see a dark ring or rust bleeding onto the wood around the fastener, pull the fastener out if possible. If the hole is wet or the wood around it is dark, rot is present at that fastener location.
- Check the ends of every deck board. The ends of boards absorb more moisture than the middle because the end grain acts like a straw. Look at the cut ends where boards meet the house, where they meet the rim joist, and at any butt joints. If the end is darker than the rest of the board, splintering, or feels soft, that board is rotting from the end inward.
- Test the railing posts. Grab each railing post near the base and try to wiggle it. If the post moves even a quarter inch, the wood at the connection point has rotted or the fasteners have corroded. Railing posts that are solid at the top but loose at the bottom are a classic sign of rot at the base.
If you find any soft spots or loose posts during this inspection, mark the area with chalk or tape. Do not assume it is minor. In Cary, where we get an average of 36 inches of rain per year and snow that sits on decks for days, even a small soft spot will grow. The question is not if it will spread, but how fast.
When to Call Burns Carpentry for Professional Deck Rot Repair
If your DIY inspection found one or two isolated soft spots on decking boards, you can handle that yourself. Replace those boards, make sure the fasteners are stainless steel or coated, and keep an eye on the area. You do not need a professional for that.
You should call Burns Carpentry when the rot is in the structural frame, meaning the joists, the ledger board, the beams, or the posts. These are load bearing components. Replacing a joist requires supporting the deck from below, cutting the rotted section out, sistering a new joist in place, and making sure the load path is continuous. That is not a weekend DIY project. A mistake there can make the deck unsafe.
Another reason to call is if you find rot in multiple areas. If you have soft spots near the house and at two different post bases, the problem is systemic. Something is causing moisture to accumulate. A professional can trace the source, whether it is a flashing failure, poor grading that lets water pool under the deck, or a gutter downspout that directs water directly at the structure. Burns Carpentry handles Deck Repairs in Cary and across McHenry County. We have seen every version of rot you can imagine, from decks that looked fine on top but had a completely rotten frame underneath, to decks where the only visible sign was a slight dip in the middle of the span.
We also handle Deck Building and Pergola Building if your existing deck is beyond repair and you want a new structure built to modern standards with proper flashing, drainage, and rot resistant materials. If you are considering replacing a rotted deck with a Composite Deck, that is a smart move in Cary because composite never rots. It does not need staining or sealing, and it handles our freeze-thaw cycles without cracking or absorbing moisture.
Preventing Future Rot: Best Practices for Cary's Climate
Prevention is cheaper than repair. Here is what works in our specific climate.
Keep water moving away from the deck. Check your gutter downspouts. If a downspout empties near a deck post or alongside the ledger board, extend it so the water discharges at least 4 feet away. Also check the slope of the ground under the deck. If water pools there after a rain, regrade the soil so it slopes away from the house and the deck footings.
Improve airflow under the deck. If your deck is less than 18 inches off the ground, consider installing a gravel bed or removing vegetation that blocks airflow. Vines growing up posts are especially bad because they hold moisture against the wood. Also, if you have a solid skirting around the deck base, make sure it has ventilation gaps. Trapped moisture under a deck is the single biggest cause of frame rot in Cary.
Use proper fasteners. If you replace boards or make repairs, use stainless steel or hot dipped galvanized screws. Standard electroplated screws corrode in 2 to 3 years in our humid summers and freeze-thaw winters. The corrosion holds moisture against the wood and creates a rot starter.
Apply a water repellent finish annually. A clear water repellent or a semi transparent stain that contains UV blockers and a water repellent additive will extend the life of a wood deck significantly. In Cary, apply it in late spring, after the last frost and before the summer humidity sets in. One coat per year is enough for most decks.
Inspect twice a year, not once. Do a quick walkthrough in early spring after the snow melts and again in late fall before the snow arrives. Spring catches the damage from winter freeze-thaw. Fall catches the wear from summer heat and humidity. A 10 minute walk with a screwdriver twice a year will save you thousands over the life of your deck.
Frequently Asked Questions
How much does it cost to repair rotted deck joists in Cary?
Replacing a single rotted joist typically costs $200 to $400 in the Cary area, including materials and labor. If the rot has spread to multiple joists or the ledger board, the cost rises to $800 to $2,500. Burns Carpentry provides free estimates and can tell you exactly what needs to be replaced before any work begins.
Can I just paint over rotted wood on my deck?
No. Painting over rot traps moisture inside the wood and makes the rot spread faster. The only correct approach is to cut out the rotted section and replace it with sound wood. Painting is a temporary cosmetic fix that will fail within one season in Cary’s climate.
Is composite decking worth the extra cost in Cary?
Yes, especially if you want to eliminate rot concerns entirely. Composite decking costs 30 to 50 percent more than pressure treated wood upfront, but it never rots, never needs staining, and lasts 25 to 30 years in our climate. Over that timeframe, it is actually cheaper than wood when you factor in maintenance costs.
Do I need a permit to replace rotted deck boards in Cary?
Replacing a few individual deck boards does not require a permit in Cary. However, replacing structural components like joists, beams, or posts does require a permit. Burns Carpentry handles all permits for structural repairs and new deck construction, so you do not have to worry about the paperwork.
If your deck failed the screwdriver test and you found soft spots in the frame or posts, do not wait for spring to fix it. Burns Carpentry offers free estimates for all Deck Repairs in Cary and the surrounding area. We will come out, inspect the damage, give you a straight answer about what needs to be done, and handle the permits if needed. Give us a call. We will tell you whether it is something you can handle yourself or whether you need us to step in before the rot gets worse.