Having proper drainage between deck boards is critical for the longevity and maintenance of your deck. When water gets trapped between the boards, it can lead to rot, mold, mildew, and faster deterioration of the wood. There are a few methods to increase drainage and expand the gaps between deck boards.
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Why Proper Drainage is Important
Wood needs to be able to dry out after getting wet. If water remains for extended periods against the wood, it will absorb deeper into the material. This moisture encourages fungal growth and attracts carpenter ants and termites. It also causes the expansion and contraction of the boards through water absorption. Over time, this leads to warping, splintering, and cracking.
With proper drainage, any water that gets between the boards can quickly flow out. This prevents saturation and deterioration. It allows the boards to easily dry between rainfalls or uses of the deck. Proper drainage extends the lifespan of the deck by slowing weathering and biological decay.
How Wide Should Drainage Gaps Be?
Most experts recommend a 1/8 inch gap between each deck board to allow for drainage and slight wood expansion. This is wide enough for water to drain through but narrow enough to not allow debris buildup.
Some alternative recommendations are:
- 1/4 inch gaps for decking made from Cedar or Redwood which expands more than other woods.
- 1/16 inch gaps if using a hidden fastener system like plugs instead of exposed screws.
- At least 1/8 inch for any exotic hardwood decking which has greater expansion such as Ipe.
The most important factor is having a consistent gap width across all boards. Varied spacing can lead to an uneven look.
Methods to Increase Drainage Gap
There are a few approaches to widen the gaps between deck boards after construction.
Add Spacers Between Boards
This involves prying up individual boards enough to slide in wood or plastic spacer material. The spacers then hold the board at the proper height as you re-secure it.
Plastic spacers are inexpensive and readily available at hardware stores. They simply slide in between boards. Cut small sections about 1-2 inches long. Tap them evenly spaced along the board with a mallet.
Thin wood strips or shims can also work as spacers. These are more prone to breaking down over time though. They should be an exterior rated wood or treated lumber. Cut into 1-2 inch pieces and install similar to the plastic spacers.
Re-Secure Boards with Wider Gaps
If your deck is secured with screws or nails, you can remove and re-attach boards with increased spacing. Here are the steps:
- Remove screws/nails from an entire board.
- Lift the board enough to slide in spacers.
- Re-secure board at new height, leaving target drainage gap.
- Insert additional screws staggered from original holes.
- Repeat for each deck board.
Use the same plastic or wood spacers held in place while screwing. For alignment, use a small spacer at each board end.
This takes more effort than adding spacers but allows full control over the gap width. Re-securing also tightens any boards that became loose over time.
Router the Sides of Boards
You can cut away material from the board sides with a router to widen gaps. Use a straight bit and guide to trim off just enough to achieve the desired spacing.
Cutting both sides makes the changes less visible. Take care not to remove too much material which would weaken boards. Doing this thoroughly also creates consistent gaps.
Replace With Wider Spaced Boards
For full control over spacing, you can remove deck boards and install new ones with intended gaps. Here are the steps:
- Remove all deck screws/nails and detach boards.
- Cut new boards to match old length.
- Install new boards with spacers for drainage gaps.
- Stagger boards to hide any differences in widths.
This achieves consistent drainage gaps without altering existing boards. It also lets you upgrade from old warped or damaged boards.
Tips for Adding Drainage
Here are some useful tips when widening deck board gaps:
- Check local building codes for any gap width requirements.
- Match the angle of existing boards to maintain the deck slope.
- Aim for 1/8 inch but make adjustments for specific wood types.
- Use spacers to keep new gaps consistent while re-securing boards.
- Stagger and blend new board spacing for the best appearance.
- Only router half the thickness from each board side.
- Re-use or sell removed boards that are still in good condition.
Conclusion
Adding drainage gaps between deck boards is an important maintenance task. Water trapped between boards will accelerate rot and decay issues. Aim for 1/8 inch spacers between all boards, adjusted slightly for certain wood varieties.
There are several methods to increase spacing from adding blocks to completely replacing boards. Any upgrade is worthwhile to extend your deck’s lifespan and reduce long-term repairs. With proper drainage and ventilation, your deck will last for decades. Maintaining these gaps and the deck surface will allow for safe, dry use for years to come.
Frequently Asked Questions
What are the benefits of wider drainage gaps?
Wider gaps allow for better drainage and air circulation between boards. This prevents water from being trapped and speeds drying after rain or use. Proper drainage helps minimize rot, mold, and premature wood decay.
Will adding spacers mess up my deck layout?
If spacers are installed carefully at a consistent thickness, they should not alter the overall deck layout. The deck will remain the same length and width. Use equal spacer intervals under each board to maintain even spacing.
How much do I need to widen gaps to improve drainage?
Most experts recommend widening to at least a 1/8 inch gap between boards. For some woods like cedar and redwood, 1/4 inch gaps may be preferred to account for greater expansion. The key is keeping the gap width even across all boards.
What type of wood makes the best spacers?
Cedar, redwood, or pressure treated lumber are ideal for wood spacers between deck boards. These are naturally rot resistant or treated for outdoor use. Avoid regular lumber like pine which will quickly decay when exposed to weather.
Will I need to re-stain my deck after widening gaps?
It’s a good idea to re-apply stain or sealer any time you disturb boards. This will ensure all wood surfaces remain protected, especially cut edges or screw holes. Match your previous finish.
References
Articles
- How to Space Deck Boards – Better Homes & Gardens
- How to Increase the Gap Between Deck Boards | Family Handyman
- Deck Board Spacing: Gapping Your Deck Boards | Bob Vila