---

Can You Use Pressure Treated Wood Indoors? Why It’s Not Recommended

Why Pressure Treated Wood Exists

Pressure treated wood was developed to solve a big problem: moisture and insects that destroy outdoor wood. The treatment process forces preservatives deep into the wood fibers under pressure, creating lumber that can withstand decades of rain, soil contact, and termites.

Outdoors, it is commonly used for decks, fences, raised garden beds (with liners), play structures, and retaining walls. Indoors, however, those threats don’t exist, and the chemical treatment becomes more of a liability than a benefit.

The Chemicals in Pressure Treated Wood

Older treated lumber once contained arsenic (CCA), but today most uses alkaline copper quaternary (ACQ) or copper azole (CA). These are safer outdoors, but not indoors. Risks include off-gassing into indoor air, dust exposure during cutting or sanding, and slow leaching onto stored items if used for shelving or furniture.

These risks are low outdoors but concentrated indoors, which is why building codes prohibit pressure treated wood inside homes except in very specific cases.

The One Exception: Sill Plates

Pressure treated lumber may be used indoors at the sill plate or bottom plate where wood touches concrete. Because concrete holds moisture, untreated wood would rot. The rule of thumb is simple: use treated lumber only where wood meets masonry, and untreated lumber everywhere else indoors.

Why Untreated Wood Is Better Indoors

Untreated wood is free of chemical preservatives, making it safe for indoor air quality and human contact. It can be painted, stained, or sealed for appearance and durability. It is also easier on tools, less expensive, and has a clean natural look without the greenish tint of treated lumber.

Common Types of Wood for Indoor Projects

Softwood Lumber (Pine, Fir, Spruce)

Affordable and easy to work with. Ideal for framing, shelving, or basic furniture projects. Needs paint or sealant for long-term durability.

Hardwoods (Oak, Maple, Cherry, Walnut)

Denser, more durable, and commonly used in furniture, cabinetry, and trim. Attractive grain patterns and long-lasting, though higher in cost.

Plywood

Engineered wood sheets made from layers of veneer. Useful for subfloors, wall sheathing, and cabinets. Cabinet-grade plywood is smooth and attractive enough for visible furniture parts.

MDF (Medium Density Fiberboard)

Made from wood fibers and resin. Smooth, stable, and excellent for trim or painted projects. Not water-resistant, so it must stay dry.

OSB (Oriented Strand Board)

Compressed wood chips and resin. Strong and economical for subflooring and sheathing, but less attractive than plywood and usually hidden behind finishes.

Choosing the Right Wood for Each Project

For framing walls, use kiln-dried spruce, pine, or fir studs, with treated lumber only at the base plate. For shelving and furniture, use hardwoods or pine. Trim and molding often work best with MDF if painting, or hardwood if staining. Cabinets typically use cabinet-grade plywood, and subfloors are built with plywood or OSB. All of these should be untreated indoors.

What Happens If You Use Pressure Treated Wood Indoors?

If you already used treated wood indoors, don’t panic. A few studs won’t instantly make a home unsafe. Still, avoid using it for shelving, furniture, or anywhere people or food have direct contact. For hidden framing, consider replacing it in sensitive areas like a child’s room. Always wear protective gear when cutting or sanding treated lumber.

Safer Alternatives for Durability Indoors

Homeowners sometimes want treated lumber indoors for durability, but there are safer ways to achieve the same goal. You can seal untreated wood with polyurethane, varnish, or paint. Use naturally rot-resistant species such as cedar for accents. Improve ventilation in damp basements and install vapor barriers between concrete and wood to reduce moisture transfer.

Frequently Asked Questions

Can you use pressure treated wood for basement framing?

Only for the bottom plate against concrete. All vertical studs and upper framing should be untreated lumber.

Is the green color in pressure treated wood harmful?

The green tint comes from copper compounds. Outdoors it is safe, but indoors it can leach and discolor stored items.

Can I use treated wood for indoor furniture if I seal it?

Not recommended. Even with sealants, wear and cutting expose treated surfaces. Safer choices are hardwoods or softwoods.

What’s the safest wood for indoor shelving?

Pine, poplar, or plywood are good budget options. Hardwoods like oak or maple are stronger for heavy loads.

How do I dispose of treated wood scraps safely?

Never burn pressure treated wood. It releases toxic fumes. Instead, take scraps to your local waste disposal site.