If you've noticed gaps opening up between the boards on your deck in Cary, IL, you're not alone. It's one of the most common questions we hear from homeowners, and the answer isn't always straightforward. In this guide, we'll walk you through why wood deck boards gap in our climate, how to tell if it's normal or a sign of rot, and exactly how to fix it, whether you tackle it yourself or call in a professional like Burns Carpentry.
Why Wood Deck Boards Gap in Cary, IL's Climate
Wood is a hygroscopic material, meaning it constantly absorbs and releases moisture based on the humidity around it. In Cary, we experience dramatic swings in humidity throughout the year, from humid summers with dew points in the 60s and 70s to dry, cold winters where indoor humidity drops to 20% or less. Each time the wood gains or loses moisture, it swells or shrinks. Over time, these cycles cause the boards to move, and gaps appear.
The type of wood you have matters too. Pressure treated pine, the most common decking material in our area, moves significantly more than cedar or redwood. A board that's 6 inches wide can shrink or expand by as much as 1/8 inch across its width with each season. That doesn't sound like much, but multiply it by 20 or 30 boards across your deck, and you'll see gaps that catch heels and collect debris.
The way your deck was built also plays a role. If the boards were installed with zero spacing between them, they'll swell and push against each other, causing cupping and crowning. If they were spaced too wide, you'll see gaps right from the start. The ideal spacing for most Wood Decks in our climate is 1/8 inch to 1/4 inch, and that gap should be maintained with a consistent spacer during installation.
How to Tell If Gaps Are Normal or a Sign of Rot
Before you start fixing gaps, you need to know whether you're dealing with normal seasonal movement or something more serious. A quick test: run your finger along the edge of the gap. If the wood feels solid and dry, it's probably just normal shrinkage. If it feels soft, crumbly, or you can press your fingernail into it, that's rot, and it needs attention before you do anything else.
Rot in deck boards is usually caused by trapped moisture. Water sits in the gaps, especially in low spots where the deck doesn't drain well, and over time it works its way into the wood fibers. In Cary, where we get an average of 38 inches of rain a year and snow that lingers for weeks, this is a real concern. Check the areas around the gaps for discoloration, a musty smell, or visible fungal growth. Also inspect the joists underneath, since rot can start there and spread upward.
If you find rot, the fix is not a simple gap filler. You need to replace the affected boards and, in some cases, the joists beneath them. This is where a professional deck repair service becomes essential. Burns Carpentry specializes in Deck Repairs and can assess the full extent of the damage before recommending a course of action. In most cases, catching rot early means replacing just a few boards, but ignoring it can lead to a full deck replacement.
4 DIY Fixes for Small Deck Gaps (and When to Call a Pro)
For gaps that are purely cosmetic and less than 1/4 inch wide, you have a few DIY options. These fixes are best for decks that are structurally sound and have no signs of rot.
1. Wood Filler or Epoxy
For very small gaps, less than 1/8 inch, you can use a high quality exterior wood filler or epoxy. Clean the gap thoroughly, let it dry completely, then press the filler in with a putty knife. Sand it smooth once it cures. This is a temporary fix at best, since the wood will still move with the seasons and the filler may crack or pop out. It's best for decks you plan to replace soon.
2. Rope or Backer Rod
For gaps up to 1/4 inch, you can use a foam backer rod, the same material used to fill expansion joints in concrete. Press it into the gap so it sits just below the surface, then cover it with a flexible deck caulk or sealant. This allows for movement while keeping debris out. It's a decent short term solution, but you'll need to reapply the sealant every couple of years.
3. Adjust the Board Spacing
If the gaps are inconsistent, with some boards tight against each other and others wide, you can sometimes pry the boards together and re-screw them with a consistent 1/8 inch gap. You'll need a pry bar, a circular saw for trimming, and a screw gun. This is labor intensive, but it can make your deck look much better. Just be careful not to split the boards when you pry them.
4. Replace Individual Boards
If a few boards have gaps wider than 1/4 inch and they're warped or cupped, replacing them is often the best DIY fix. You can match the wood type and use a circular saw to cut out the old board, then screw in the new one with proper spacing. This is a weekend project for a handy homeowner, but it requires precision to avoid tripping hazards and to keep the surface even.
When should you call a pro? If the gaps are widespread, if you suspect rot, or if your deck is more than 10 years old and you're planning to replace it anyway, skip the DIY route. A professional Deck Building or deck repair service like Burns Carpentry can assess the entire structure, recommend whether to repair or replace, and do the job right. They'll also catch issues you might miss, like loose railings or corroded fasteners.
Replacing Warped Boards: Step-by-Step for Cary Homeowners
If you've decided to replace a few warped boards yourself, here's the step by step process that works for most wood decks in Cary. It's a bit more involved than just pulling up the old board, but doable with the right tools.
- Remove the old board. Use a pry bar to lift the board, being careful not to damage adjacent boards. If the board is screwed down, find the screws first and remove them with a drill. If it's nailed, you may need to use a reciprocating saw to cut the nails.
- Check the joists. Once the board is off, inspect the joists for rot or damage. If the joists are soft or discolored, stop and call a professional. Replacing a joist is a structural job best left to experts.
- Cut the new board to length. Use a circular saw with a fine finish blade to cut the new board to fit. Leave a 1/8 inch gap at the ends to allow for expansion.
- Pre-drill the screw holes. To prevent splitting, pre-drill holes about 1 inch from each end and every 12 to 16 inches along the board. Use a countersink bit so the screw heads sit flush with the surface.
- Attach the board with a spacer. Place a 1/8 inch spacer (a piece of plywood or a deck spacer tool) between the new board and the adjacent one. Drive the screws through the pre-drilled holes, making sure the board is level and even with the surrounding surface.
- Seal the edges. Apply a wood preservative or sealant to the cut ends to prevent moisture from wicking in. This is a step many DIYers skip, but it's critical in our climate to prevent rot.
This process works well for a few boards, but if you're replacing more than 20% of your deck surface, you might be better off with a full deck replacement. New deck construction by Burns Carpentry can give you a fresh start with proper spacing and high quality materials that will last longer and require less maintenance.
Preventing Future Gaps: Sealing, Spacing, and Maintenance
Once you've fixed your gaps, the goal is to keep them from coming back. The three pillars of prevention are sealing, spacing, and regular maintenance.
Sealing: A good quality waterproofing sealant is your deck's first line of defense. It helps the wood repel moisture, reducing the swelling and shrinking that causes gaps. In Cary, where we have cold winters and hot summers, you should plan to seal your deck every 2 to 3 years for pressure treated wood, and every 1 to 2 years for cedar. Use a sealant with UV protection to prevent graying, and apply it on a dry day when the forecast is clear for at least 48 hours.
Spacing: If you're building a new deck or replacing boards, always use a spacer to maintain a consistent gap. The standard is 1/8 inch to 1/4 inch for wood, and you can buy plastic spacers at any hardware store. Consistent spacing allows for movement without creating trip hazards or catching debris.
Maintenance: Sweep your deck regularly to remove leaves and dirt that hold moisture. Once a year, inspect for loose screws, popped nails, and any signs of rot, especially around the posts and stairs. In Cary, it's also a good idea to clear snow promptly in winter and to use a plastic shovel to avoid gouging the wood.
If you're tired of yearly maintenance and want a deck that needs almost none, consider composite decking. Burns Carpentry builds Composite Decks that never need sealing or staining, and they're resistant to rot, warping, and insects. The initial cost is higher, typically $40 to $60 per square foot installed in the Cary area, but you'll save money over time on maintenance and replacement.
Frequently Asked Questions
How much does it cost to fix deck gaps in Cary, IL?
The cost depends on the scope. DIY fixes like filler or caulk cost under $50. Replacing a few boards costs $200 to $500 for materials if you do it yourself. Hiring a professional deck repair service like Burns Carpentry typically runs $500 to $1,500 for a few boards, including labor and materials.
Can I just fill the gaps with caulk?
You can, but it's not a permanent fix. Caulk will eventually crack and peel as the wood moves. For a longer lasting solution, use a flexible sealer or replace the boards if the gaps are large.
Is composite decking worth the extra cost?
For many Cary homeowners, yes. Composite decks cost more upfront but last 25 to 30 years with minimal maintenance, compared to 10 to 15 years for wood. If you plan to stay in your home for more than a few years, the long term savings often justify the higher initial investment.
How do I know if my deck is safe to walk on?
If you have gaps wider than 1/4 inch, loose boards, or any soft spots, have it inspected before heavy use. A professional can check the structural integrity and let you know if repairs are needed. Burns Carpentry offers free estimates and can advise you on the best course of action.
If your deck gaps are beyond a simple DIY fix, or if you're ready for a new deck that won't gap for decades, Burns Carpentry is the local choice in Cary. We build and repair decks that stand up to Illinois weather, and we'll tell you straight up whether a repair or replacement is the smarter investment. Call us for a free estimate.
