Key Takeaways
- Pressure treated wood contains chemical preservatives that make it resistant to rot, fungus, insects and, depending on the level of preservatives, contact with the soil.
- Pressure treated lumber has some moisture resistance but requires a sealer for the best moisture protection.
- Pressure treated wood is the best, longest lasting choice for outdoor structures like fences and decks.
- Untreated wood offers a lower purchase price, more natural beauty and is easy to stain or paint.
- Untreated wood has no chemical preservatives and is best for indoor projects like installing molding or for wall studs, where the wood isn’t exposed to weather.
- Untreated woods like cedar and redwood are exceptions since natural rot and insect resistance make them good choices for many outdoor projects.
What’s Pressure Treated Wood?
Pressure-treated wood is lumber that has a chemical preservative added for resistance to decay, insects and fungus. High pressure forces the chemical deep into the wood to create lumber products for long-lasting outdoor projects. Pressure treated wood is available in two types:
- Above Ground: Above-ground treated wood is for use more than six inches above the soil. For example, railing and decking boards on a wood deck can typically be above-ground pressure treated wood.
- Ground Contact: Ground-contact treated wood has more preservatives and is for use at or near ground level or in parts of a structure that are critical and difficult to replace. Fence posts and deck frame components typically need to be rated for ground contact.
Local building codes specify suitable lumber for different uses. Always follow the building codes for your area.
Benefits of Pressure Treated Wood
- Durability: The chemical treatments give treated wood a longer lifespan in outdoor projects than untreated wood.
- Moisture Resistance: While treated wood isn’t waterproof, it’s more resistant to moisture and rot than untreated wood.
- Insect Resistance: Treated wood is less appealing to termites and other insects than untreated wood.
- Ground Contact: Ground-contact treated wood lasts longer in or on the soil than untreated lumber.
In addition, pressure treated wood is necessary for building code compliance for many outdoor structures, such as deck frames and post footings.
Uses for Pressure Treated Wood
Treated lumber is the right wood for outdoor projects and some indoor projects where there’s risk of moisture or decay. Uses for pressure treated lumber include:
- Building deck frames
- Installing wood deck boards
- Constructing a wood fence
- Building a sandbox
- Building outdoor furniture
- Subflooring on a concrete slab
Although pressure treated wood is designed for outdoor use, it requires staining and sealing or a couple of coats of outdoor paint to protect it from ultraviolet rays and to improve moisture resistance.
What’s Untreated Wood?
As the name suggests, untreated wood doesn’t have the chemical preservative of pressure treated wood, so most types are best for indoor use.
Benefits of Untreated Wood
- Ease of Painting and Staining: Untreated wood accepts paint and wood stain better and faster than treated wood, which can take weeks or months to dry enough for painting and staining.
- Natural Appeal: Untreated wood has natural warmth and beauty since it doesn’t have the greenish tint pressure treated wood often has.
- Fastener Compatibility: Untreated wood doesn’t require fasteners with specialized corrosion resistance like treated wood.
- Lower Cost: Untreated wood is a less expensive purchase than comparable treated wood.
Uses for Untreated Wood
Untreated wood is usually the best choice for indoor projects where there’s low risk of moisture. Uses for untreated wood include:
- Installing moulding and trim
- Building tables, desks and other indoor furniture
- Building shelves and bookcases
- Building a DIY workbench
- Crafting
- Wall studs, where the wood isn’t exposed to the elements
Some untreated wood, such as redwood or cedar, has natural resistance to insects and rot that makes it suitable for outdoor use. While you can use standard untreated wood outdoors, it requires much more maintenance than treated wood and isn’t suitable for structural components like deck posts and framing.
Treated Wood vs. Untreated Wood: Which Is Best for You?
The right wood for any project depends on several factors, including building codes, humidity levels and climate. However, in most cases, choosing between treated and untreated wood depends on where you plan to use the wood. Pressure treated wood is best for most outdoor projects, while untreated wood is best for most indoor projects.
However, when you do have a choice, use these factors to decide:
- Lifespan: Treated lumber can last for decades outdoors with proper care. Untreated lumber, even with regular maintenance, often only lasts up to five years outdoors. However, untreated wood can last for several decades indoors.
- Expense: Untreated wood is a less expensive purchase than treated wood. However, if you plan to use it outside, the higher maintenance expenses for untreated wood and eventual replacement costs can make it less economical over the years.
- Appearance: Untreated wood has a more appealing, natural appearance. While you can stain or paint both treated and untreated wood, untreated wood takes the stain more easily.
Get the Right Lumber for Your Project
Whether you need treated lumber for a deck or untreated crown molding to add elegance to a room, you can shop Lowes.com by type, size, species and more to give your work professional results. If you’re not sure which type of wood is best for you, visit your local Lowe’s and talk with one of our Red Vest associates. They’ll help you find the right lumber, as well as the tools, fasteners and paint, stain and sealer you need to do the work right.