If your wood deck is starting to slope toward the yard, or you've noticed a gap between the house and the deck frame, you're not alone. In Cary, IL, where freeze-thaw cycles are brutal and the soil is heavy with clay, sinking decks are one of the most common structural problems we see. The fix isn't just about jacking it back up; it's about understanding why it sank in the first place, and that's where most homeowners get it wrong. This 2026 guide will walk you through the real causes, the warning signs, and the exact repair process, including what it costs in our area.
Why Your Wood Deck Is Sinking: Top Causes in Cary, IL
Most people assume a sinking deck is a sign of rotten wood, and that's sometimes true. But in the Chicago suburbs, the real culprit is almost always the ground beneath the deck. The soil in Cary is predominantly clay, which expands when wet and contracts when dry. Add in the repeated freeze-thaw cycles we get from November through March, and you've got a recipe for footings that shift, heave, and settle unevenly.
The second most common cause is improper footing depth. Many decks built before the mid-2000s in our area were installed with footings that only go 24 to 30 inches deep. The current building code in McHenry County requires footings to extend below the frost line, which is about 42 inches in Cary. If your deck's footings weren't dug deep enough, every winter the ground under them freezes and thaws, slowly pushing and pulling the posts until the whole structure starts to tilt. I've personally seen decks that were perfectly level in 2010 now sitting 4 to 6 inches lower on one corner.
Finally, poor drainage is a silent killer. If your downspouts dump water right next to the deck posts, or if the grade of your yard slopes toward the house, you're constantly saturating the soil around the footings. Over time, that softens the ground and allows the posts to sink. This is why you'll often see one side of a deck sinking more than the other, it's usually the side where water collects.
5 Signs Your Deck Is Sinking (and How to Check)
You don't need to be a structural engineer to spot a sinking deck. Here are the five most reliable indicators, and most of them you can check in under ten minutes with a level and a tape measure.
- Visible slope: Place a 4-foot level on the deck boards in several spots. If you get more than a 1/4 inch drop over 4 feet, you've got settlement.
- Gap between deck and house: The ledger board should sit flush against the house. If you can slide a quarter into the gap, the deck is pulling away, a serious safety issue.
- Cracked or separated posts: Look at the bottom of each support post where it meets the footing. Hairline cracks are normal, but cracks wider than 1/8 inch or posts that have shifted sideways are red flags.
- Sticking doors or windows: If the door leading to your deck suddenly sticks, that's not a coincidence. A sinking deck can twist the house framing enough to affect door alignment.
- Water pooling on the deck surface: After a rain, check for puddles that don't drain. If water sits in the middle of the deck, the structure has already lost its crown.
If you catch any of these signs early, you can often fix the problem for a few hundred dollars. Wait until the deck is noticeably sloped or the railing feels loose, and you're looking at a much bigger project.
DIY vs. Professional Repair: What's Actually Safe in Cary
Let's be honest: some Deck Repairs are totally DIY-friendly. Replacing a few rotten deck boards, tightening loose railing balusters, or re-securing a loose stair stringer are all jobs a competent homeowner can handle with basic tools and a weekend. I'm not going to tell you to call a pro for every squeaky board.
But a sinking deck is different. This is structural, and the stakes are high. Lifting a deck that's settled means either digging out and replacing footings, or using hydraulic jacks to raise the frame and then re-pour concrete. Both require heavy equipment, a solid understanding of load distribution, and knowledge of local codes. In Cary, any repair that involves structural components needs a permit from the Village of Cary's Building Department. A homeowner can pull a permit, but you'll be responsible for meeting the 2021 International Residential Code (IRC) as adopted by Illinois, including specific requirements for post-to-footing connections and ledger flashing.
Here's the thing about DIY structural repairs: if you get it wrong, you're not just risking a wobbly deck. You're risking collapse. A deck that's 8 feet off the ground can hold several thousand pounds of people and furniture. When a footing fails, it fails fast. I've seen decks that were "fine" one week and detached from the house the next. The cost of a professional repair is a fraction of the cost of a medical bill or a lawsuit.
If you're in the Cary area and your deck is sinking more than an inch or two, or if you notice any of the more serious signs like a ledger gap, I strongly recommend getting a professional assessment. Burns Carpentry, for example, offers free estimates and will tell you straight up whether it's a simple fix or a full rebuild.
Step-by-Step Repair Process for Sinking Decks
When a deck repair is done right, it follows a methodical process. Here's what you should expect, whether you hire Burns Carpentry or another qualified contractor in the area.
- Initial assessment and inspection: A professional will examine the entire deck, not just the sinking area. They'll check the ledger board, the footings, the joists, and the beam-to-post connections. They'll also look for signs of rot or insect damage that might complicate the repair.
- Permit application: If the repair involves structural work, the contractor will pull a permit with the Village of Cary. This ensures the work is inspected and meets code.
- Support and lifting: The deck is carefully supported with adjustable steel posts or hydraulic jacks. The goal is to lift slowly and evenly, monitoring for any cracking sounds or movement. A good contractor will lift a few inches at a time, checking for level as they go.
- Footing repair or replacement: Depending on the cause, the old footings may be dug out and replaced, or new concrete may be poured alongside the existing footings. In Cary, the new footings will be dug to 42 inches deep, with a bell-shaped base and a rebar-reinforced concrete pier.
- Post and connection repair: The support posts are reattached to the footings using galvanized post anchors, and the beam-to-post connections are reinforced. This is also the time to replace any rotted wood that was discovered.
- Leveling and final inspection: Once the deck is level, the jacks are removed, and the contractor schedules a final inspection with the village. They'll also check that the deck is still properly attached to the house.
This process typically takes one to three days for a standard deck, depending on how many footings need attention. The most important thing is that the repair addresses the root cause. If you just jack the deck back up and don't fix the drainage or the shallow footings, it will sink again within a few years.
2026 Cost Breakdown: What Cary Homeowners Pay to Fix a Sinking Deck
Costs for deck repair in the Chicago area vary widely based on the severity of the problem and the size of the deck. In 2026, here's what Cary homeowners are typically paying:
- Minor shimming and leveling: If the deck has settled only 1/2 inch or less, a contractor might be able to install shims or adjust the post bases. Expect to pay $300 to $800.
- Replacing a single footing: If only one corner is sinking and the footing needs to be dug out and re-poured, the cost is usually $1,200 to $2,500, including labor and materials.
- Full footing replacement (multiple corners): When two or more footings are compromised, you're looking at $3,000 to $7,000. This is the most common scenario for decks built before 2010 in our area.
- Structural rebuild: If the sinking has caused secondary damage to the frame, joists, or ledger, the cost can climb to $8,000 to $15,000. This is essentially a partial rebuild, and it's often more cost effective to tear it down and start fresh.
These prices include permits, materials, and labor in the Cary and McHenry County market. They assume you're hiring a licensed and insured contractor. If you're tempted to go with the cheapest bid, remember that you get what you pay for. A reputable company like Burns Carpentry will use galvanized hardware, concrete that's properly mixed, and will stand behind their work with a two year workmanship warranty.
The best way to avoid these costs is prevention. Keep your downspouts directed away from the deck, make sure the ground slopes away from the house, and inspect your deck every spring after the ground thaws. If you catch a problem early, you can often fix it for the price of a few bags of concrete and a weekend of labor.
Frequently Asked Questions
How long does it take to fix a sinking deck?
Most repairs take one to three days, but it depends on the extent of the damage. A simple footing replacement might be done in a day, while a full structural repair could take a week if the deck needs to be partially dismantled.
Can I claim deck repair on my homeowners insurance?
Typically, no. Insurance covers sudden, accidental damage like a tree falling on the deck, but not gradual settling or deterioration. If your deck sank due to a burst pipe or other covered event, you might have a claim, but it's best to check with your agent.
Is it safe to use the deck while waiting for repairs?
If the deck is noticeably sloped or you see a gap between the deck and the house, avoid heavy use. A sinking deck is a structural issue, and the risk of collapse increases with every freeze-thaw cycle. It's best to limit access until a professional assesses it.
What's the difference between a sinking deck and a leaning deck?
A sinking deck drops vertically, while a leaning deck tilts to one side. Leaning is often caused by a failed footing or post, and it's more dangerous because it indicates a lateral shift. Both require immediate attention.
If your deck in Cary is starting to sink, don't wait until it becomes a bigger problem. Burns Carpentry has been fixing and building decks across McHenry County for years. We'll come out, take a look, and give you an honest assessment. If it's a simple fix, we'll tell you that too. Give us a call and let's get your deck back to level.
