When building a deck or any outdoor structure, choosing the right product for the understructure can make or break your project. Traditional pressure-treated wood is the top choice, but it comes with challenges like warping, shrinking, and excessive moisture.
These issues can lead to shrinking, longer finishing times, and added labor. If you're looking for a more stable, durable alternative, you may have come across KDAT (Kiln-Dried After Treatment) lumber, but what is this product, and is it worth the investment?
At Custom Built, we’ve worked with all types of lumber and understand how each performs in real-world conditions. KDAT lumber has unique advantages that can improve both the quality of your build and the ease of installation.
In this article, we’ll dive into what makes KDAT lumber different, its pros and cons, and where it works best. Whether you’re a homeowner planning a deck or a contractor looking for better material options, you’ll walk away with the knowledge you need to decide if KDAT is right for your next project:
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What is KDAT Lumber?
Kiln-Dried After Treatment (KDAT) lumber is pressure-treated wood that has undergone an additional drying process in a controlled kiln environment.
Unlike standard pressure-treated lumber, which is often saturated with moisture after treatment, KDAT lumber is dried to a more stable moisture level, reducing common issues like warping and shrinking.
This added step enhances the wood’s stability and usability, making it a preferred choice for decking, framing, and other structural applications.
Pros of KDAT Lumber
1. Greater Stability
KDAT lumber undergoes a controlled drying process after being pressure-treated, reducing the chances of warping, twisting, and shrinking. This stability helps maintain an even surface, especially in decking applications.
- Prevents uneven decking surfaces: Regular pressure-treated wood can dry unevenly, leading to an inconsistent top surface. KDAT lumber minimizes this issue.
- Less movement over time: Compared to standard pressure-treated lumber, KDAT remains more dimensionally stable.
2. Faster Finishing
Since KDAT lumber has a lower moisture content, it’s ready for staining, sealing, or painting much sooner than traditional pressure-treated wood. Standard pressure-treated lumber may take weeks or even months to dry out completely before it can properly accept a finish.
- Reduces project timelines: Stain or paint can be applied almost immediately.
- Ensures a more even application: Less moisture means the stain penetrates more consistently.
3. Durability
KDAT lumber retains all the durability benefits of standard pressure-treated wood while offering additional resistance to environmental stresses.
- Still pressure-treated for decay and insect resistance: KDAT is just as resilient as traditional pressure-treated wood against rot and pests.
- Reduced risk of splitting and checking: The controlled drying process minimizes surface cracking over time.
4. Smoother Appearance & Natural Aesthetic
Unlike traditional pressure-treated lumber, which often has a greenish hue due to chemical treatment, KDAT lumber has a more natural, brownish appearance that resembles unstained wood.
This means that it is:
- Easier to integrate into natural outdoor settings
- A smoother surface with fewer imperfections
5. Lighter Weight
One of the biggest advantages of KDAT lumber is that it is significantly lighter than standard pressure-treated wood.
- Up to 30% lighter: Easier to handle and install.
- Less strain on deck builders and outdoor living space contractors: Helps reduce fatigue and physical stress, especially when working with large deck components.
Cons of KDAT Lumber
1. Higher Cost Than Standard Pressure-Treated Wood
KDAT lumber is more expensive than standard pressure-treated wood due to the additional kiln-drying process.
- Additional production step: The drying process adds time and energy costs.
- Typically costs more per board foot: Though this is offset by its advantages, the upfront expense is higher.
2. Requires Proper Storage
Due to its lower moisture content, KDAT lumber must be stored correctly to maintain its benefits.
- Should be kept in a dry, covered environment: Exposure to excess moisture before installation can counteract the drying process.
- Proper stacking is essential: Avoiding direct ground contact prevents unnecessary moisture absorption.
3. Limited Availability
KDAT lumber is not as widely available as standard pressure-treated wood, making sourcing more challenging.
- Fewer suppliers carry it: Not all lumber yards stock KDAT options.
- Michigan-specific supply constraints: Pressure-treating plants in Michigan may have limited KDAT production.
Best Uses for KDAT Lumber
KDAT lumber is ideal for projects requiring stability, durability, and a smooth finish. Some of its best applications include:
1. Decking & Outdoor Structures
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- Ideal for deck boards, railings, and framing: Provides a smooth, even surface that resists warping.
- Great for pergolas and gazebos: Aesthetic benefits complement outdoor structures.
2. Structural Framing
- Most commonly used in floor joists and beams: Offers greater stability, reducing post-installation movement.
- Used in high-end residential and commercial applications: Ensures long-term durability in exposed structures.
3. Specialty Woodworking Projects
- Furniture and outdoor benches: Less moisture content means a more refined end product.
- Fencing and gates: Maintains shape and appearance over time.
Wood Grading: Choosing the Right Quality
Lumber grading affects the structural integrity and aesthetic appeal of your project. Higher-grade lumber has fewer imperfections, making it a better choice for visible areas like decking surfaces, while lower grades may be more suitable for structural framing.
- Number 1 and Better (Comparable Option: KDAT Lumber): The highest quality, with minimal defects and a mostly clear appearance. Ideal for premium decking, handrails, and exposed structures where aesthetics matter.
- Number 2 and Better (Comparable Option: Cedar): Common for deck framing and joists, offering a balance of strength and appearance. This grade is comparable to cedar in quality and is frequently used in residential decking.
- Number 3 and Better (Comparable Option: Pine): A lower grade with more knots, wane, and imperfections. While it may be more budget-friendly, it is often used for structural elements that won’t be visible rather than finished surfaces.
Profile Options: Ensuring Proper Fit and Performance
Choosing the correct lumber profile is just as important as selecting the right grade. The wrong profile can compromise your project’s stability, aesthetics, and long-term performance.
- Rail Components & Structural Posts: KDAT lumber is commonly available in 2x4s, 2x6s, 4x4s, 6x6s, and 2x2s, making it ideal for handrails, rail posts, and other vertical elements that require straight, stable pieces.
- Decking Boards: For the walking surface of your deck, KDAT wood typically comes in 5/4x6 and 2x6 sizes. These boards offer a smoother, more refined look and help reduce cupping or warping over time.
- Joists, Stringers & Beams: When it comes to supporting your deck’s structure, KDAT is often available in 2x8, 2x10, and 2x12 profiles. These sizes are ideal for joists, stair stringers, and load-bearing beams where strength and dimensional stability are critical.
Why It Matters
Selecting the right grade and profile ensures that your deck or structure is visually appealing, structurally sound, and long-lasting.
A well-informed choice can prevent issues like warping, uneven surfaces, and early wear, ultimately saving you time and money on future repairs. Before purchasing, check with your supplier to confirm availability and compatibility with your project’s needs.
Next Steps to Building or Remodeling Your Outdoor Living Space
KDAT lumber offers superior stability, a smoother finish, and easier installation compared to standard pressure-treated wood. However, its higher cost and storage needs may not suit every project.
If you value durability, aesthetics, and ease of installation, KDAT is a smart investment. If budget and availability are top concerns, traditional pressure-treated wood may be a better fit.
At Custom Built, we help homeowners choose the best materials for their decks and outdoor spaces, ensuring a balance of quality, style, and budget.
Thinking about using KDAT lumber? Reach out to a Custom Built team member to explore your options, design possibilities, and expert installation guidance for a long-lasting outdoor space.
Now that you know more about KDAT lumber, let’s explore how much lighting and composite decks cost and Trex’s high-quality composite lines:
- How Much Does Deck Lighting Cost in Michigan? - Discover how much Trex and other deck lighting options cost and what affects the estimate.
- How Much Do Composite Decks Cost in Lansing, Michigan? - An overview of how much your Lansing composite deck will cost and the factors that will influence your price.
- Comparing Trex Lineage, Transcend, Select, and Enhance Composite Decking Lines - Explore our thorough comparison of Trex’s most common composite decking options, including cost, colors, and benefits.
