Introduction
If your deck feels spongy underfoot or shows dark, crumbling spots, it’s time to learn how to replace rotten deck boards. Wooden decks are constantly exposed to rain, humidity, sun, and foot traffic. Over time, boards can rot—especially if sealant wears off or water pools in certain areas. Replacing damaged boards not only restores your deck’s beauty but also ensures safety and prevents further decay.
Why Replacing Rotten Boards Matters
Rotten boards aren’t just unsightly—they create real hazards. By replacing them, you’ll:
- Improve Safety: Prevent trips, falls, and possible board collapse.
- Extend Deck Life: Stop rot from spreading to surrounding boards and framing.
- Boost Curb Appeal: Restore a fresh, clean look to your outdoor space.
- Save Money: Timely repairs prevent the need for a full deck replacement later.
Ignoring rotten boards allows moisture to penetrate deeper into the frame, leading to costly structural damage.
Step-by-Step Guide to Replacing Rotten Deck Boards
1. Inspect the Deck
Walk across the deck and look for:
- Soft or spongy areas underfoot.
- Dark stains or crumbling wood.
- Boards that flex or sag when stepped on.
Mark each board that needs replacing with chalk or tape.
2. Gather Tools and Materials
You’ll need:
- Circular saw or jigsaw
- Pry bar or hammer
- Tape measure and pencil
- Drill and deck screws
- Replacement boards (pressure-treated or rot-resistant wood)
- Safety gear: gloves, safety glasses, dust mask
3. Remove Damaged Boards
Use a pry bar to lift boards from the joists. If boards are nailed down, pull nails carefully. For stubborn boards, cut them into smaller sections with a saw, then remove piece by piece. Dispose of rotten boards safely—they may crumble as you handle them.
4. Inspect the Joists
Once the boards are removed, inspect the joists underneath. If joists show signs of rot or weakness, they may also need repair or reinforcement. Never replace boards without checking the structural base first.
5. Measure and Cut New Boards
Measure the length of the removed board. Mark and cut new boards using a circular saw. Always cut slightly longer if in doubt, then trim for a snug fit.
6. Pre-Drill Holes
To prevent splitting, pre-drill holes in replacement boards where screws will go. Align holes with the joists underneath.
7. Install Replacement Boards
Lay the new board into position. Use galvanized or stainless-steel deck screws to secure it firmly to the joists. Screws are preferable to nails—they hold stronger and are easier to remove if future repairs are needed.
8. Ensure Proper Spacing
Leave a 1/8-inch gap between deck boards for drainage and expansion. Consistent spacing prevents water buildup and extends deck life.
9. Sand and Blend
If the replacement boards sit slightly higher or rougher than surrounding ones, sand them down for a smooth, level surface. This also helps blend the new wood with the old.
10. Stain or Seal the Deck
Once all boards are replaced, apply a quality sealant or stain. This protects against water penetration, UV damage, and future rot. Apply evenly across the entire deck for a uniform look.
Common Mistakes to Avoid
- Mistake: Replacing Boards Without Checking Joists
Rot often spreads below the surface.
Solution: Inspect and repair joists before installing new boards. - Mistake: Using Untreated Lumber
Regular wood won’t withstand outdoor conditions.
Solution: Use pressure-treated lumber or rot-resistant woods like cedar or redwood. - Mistake: Nailing Instead of Screwing
Nails loosen over time, leading to instability.
Solution: Use deck screws for a stronger, longer-lasting hold. - Mistake: Skipping Gaps Between Boards
Boards without gaps trap moisture and warp.
Solution: Maintain 1/8-inch spacing for drainage. - Mistake: Forgetting to Seal
Unsealed boards rot faster.
Solution: Always apply sealant or stain after replacing boards.
Extra Patio & Deck Tips & Hacks
- Replace boards in groups if multiple are rotten—this creates a more uniform appearance.
- Label removed boards and use them as templates for cutting new ones.
- For composite decking upgrades, check if existing joists can support the new material.
- Schedule annual inspections to catch early signs of rot before they spread.
Want to keep your deck looking fresh? See our guide on how to clean a wooden deck without damaging it.
Conclusion
Learning how to replace rotten deck boards is one of the most important maintenance tasks for any homeowner with a wooden deck. By removing damaged boards, checking the joists, and installing treated replacements, you’ll restore your deck’s safety, strength, and beauty.
Pro tip: Prevention is always better than repair—regular cleaning and sealing can add years to your deck’s life. Bookmark this guide to have step-by-step instructions ready whenever a board needs replacing.