Can You Shim Deck Boards: A Comprehensive Guide

Ever found yourself with a deck that's seen better days, with boards that have shifted or warped over time? You might be wondering, "Can you shim deck boards?" The answer is yes, and it's a great way to restore your deck's stability and safety. Let's dive into the world of deck shimming, exploring what it is, when you need it, and how to do it.

Deck shimming is the process of inserting thin pieces of material, known as shims, between the deck boards and the joists below to correct unevenness and ensure a level surface. It's a simple yet effective technique that can save you from expensive deck replacement or repair.

When to Shim Deck Boards

Before you reach for your shims, it's crucial to understand when deck shimming is necessary. Here are two key scenarios:

Uneven Deck Surface: If your deck has a noticeable slope or is uneven, it's a sign that the boards have shifted or the joists have settled. Shimming can help level the surface and improve safety.

Identifying the Problem

Walk across your deck, paying close attention to any areas that feel soft, bouncy, or uneven. Mark these spots for further inspection. You can also use a level to identify low spots.

Once you've identified the problematic areas, measure the gap between the deck board and the joist. If it's more than 1/8 inch, shimming is likely necessary.

Preventing Further Damage

Shimming isn't just about aesthetics; it's also about preventing further damage. An uneven deck can lead to water pooling, which can cause rot and weaken the structure. By shimming, you're promoting proper water drainage and prolonging your deck's lifespan.

Choosing the Right Shim Material

Now that you've identified the areas that need shimming, it's time to choose the right material. The best shims are made from durable, weather-resistant materials that won't rot or warp over time. Here are a few options:

Pressure-Treated Lumber: This is a popular choice for deck shimming due to its durability and resistance to rot and insects. It's also widely available and affordable.

Composite Materials: If your deck is made from composite materials, using composite shims can help maintain a consistent look and feel. However, they can be more expensive than lumber.

Hardwood: Hardwood shims are another option, but they're typically more expensive and may not be as durable as pressure-treated lumber or composite materials in outdoor applications.

Size Matters

When choosing shims, ensure they're thin enough to fit into the gap between the deck board and the joist. Standard shims are typically 1/8 inch or 1/16 inch thick, but you can also cut them down to size if needed.

Remember, the goal is to create a level surface, so you may need to use shims of different thicknesses in different areas. It's better to use multiple thin shims than one thick one, as this will provide a more stable and level surface.

Preventing Future Movement

To prevent the shims from moving over time, consider using construction adhesive or screws to secure them in place. This will help ensure that your shimming efforts last for years to come.

Shimming Your Deck: A Step-by-Step Guide

Now that you've identified the areas that need shimming and chosen the right materials, it's time to get to work. Here's a step-by-step guide to shimming your deck:

Step 1: Gather Your Tools: You'll need a pry bar, a tape measure, a saw (hand saw or circular saw), a drill (if using screws), a level, and your chosen shim material.

Step 2: Remove the Deck Board: Use the pry bar to carefully lift the deck board off the joist. You may need to remove screws or nails first. Set the board aside for now.

Measuring and Cutting the Shim

Measure the gap between the joist and the underside of the deck board. Cut the shim to this length using your saw. If the gap is less than the width of the shim, you can cut the shim to width as well.

Step 3: Insert the Shim: Place the shim between the joist and the underside of the deck board. Use the level to ensure the board is level with the surrounding boards. If the shim is too thick, you can cut it down to size.

Step 4: Secure the Shim: If you're using construction adhesive, apply a bead along the top of the shim before placing the deck board back on top. If you're using screws, drill pilot holes through the deck board and into the shim, then secure the board with screws.

Step 5: Replace the Deck Board: Carefully replace the deck board, ensuring it's level with the surrounding boards. If you're using screws, you may need to countersink the heads to prevent them from sticking up.

Step 6: Repeat the Process: Repeat these steps for each area that needs shimming. Remember to use shims of different thicknesses as needed to create a level surface.

Finishing Up

Once you've shimmed all the necessary areas, take a step back and admire your handiwork. Your deck should now be level and stable, ready for years of enjoyment.

Regular maintenance is key to keeping your deck in tip-top shape. Make a habit of inspecting your deck annually, looking for any signs of wear or damage. With proper care, your deck shimming efforts will serve you well for years to come.

So, can you shim deck boards? Absolutely, and it's a skill worth having in your home maintenance toolkit. Not only will it improve the safety and longevity of your deck, but it's also a rewarding DIY project that can save you money. Happy shimming!