Nearly every deck in Georgia stands on pressure treated wood. It is the frame under every composite deck we build and the posts holding up every porch. In fact, it remains the most popular decking surface in the state by a wide margin. Yet most homeowners misunderstand it. They buy the wrong treatment level, stain at the wrong time, or pair it with the wrong screws. Then they watch the connections fail early.
This guide covers what pressure treated lumber actually is and which types and grades matter on a deck. It also explains the timing rules that decide whether your stain lasts five years or one. It comes from a crew that frames with this material every working week across North Georgia.
What Pressure Treated Wood Actually Is
Pressure treated lumber starts as ordinary wood, almost always southern yellow pine here in the Southeast. The mill then seals it inside a pressure vessel and forces preservative deep into the wood fibers. The preservative is what makes the board resist rot, fungal decay, and termites for decades instead of years.
Modern residential lumber relies on copper-based preservatives. Micronized copper azole, usually shortened to MCA, now dominates the residential market, alongside copper azole (CA-C) and alkaline copper quaternary (ACQ). Meanwhile, the old arsenic-based CCA formula left residential lumber back in 2004. As a result, the boards at today’s lumberyard are a different product than the deck your parents had. The faint green or brown tint on fresh boards is the copper reacting with the wood, and it fades as the lumber weathers.
Types of Pressure Treated Wood
The type that matters is not the brand on the tag. Instead, look at the use category. This rating from the American Wood Protection Association tells you where a board can live. Every treated board carries an end tag with its category. Reading it correctly separates a deck that lasts from posts that rot at the soil line.
| Use category | Treatment level | Where it belongs on a deck |
|---|---|---|
| Above ground (UC3B) | Standard | Deck boards, railings, and framing that stays well above grade with good airflow |
| Ground contact (UC4A) | Roughly twice the preservative retention | Posts, anything touching soil or embedded in concrete, framing within about 6 inches of grade, and spots where debris or poor ventilation trap moisture |
| Heavy duty (UC4B) | Highest residential retention | Critical structural pieces in severe, wet, hard-to-replace locations |
The mistake we correct most often on repair calls: above-ground boards used as ground-contact posts. They look identical in the stack. However, the preservative retention is not the same. Georgia clay holds enough moisture to find that out for you.
One more type worth knowing, because demand for it is climbing fast: KDAT, kiln dried after treatment. Standard treated lumber leaves the plant soaked with treatment solution. KDAT, however, goes back into the kiln after treating. As a result, it arrives dry, straighter, lighter, and ready to stain almost immediately. It costs more per board and saves you a season of patience.
Treated Lumber Grades
Treatment level tells you where a board can go; grade tells you how good the wood itself is. For deck work, two structural grades cover almost everything:
- #1 grade: fewer and smaller knots, straighter grain, fewer wane edges. The right call for visible surfaces and long spans.
- #2 grade: the everyday framing standard. Structurally sound and code-accepted for joists and beams, with more knots and character than #1.
Above those sit appearance-driven decking boards often sold as premium or select, milled with rounded edges and culled for looks. Our rule on real builds is simple: the frame can be #2 all day. However, the boards you walk on and the rails your hands touch earn the upgrade. A knot that pops out of a joist is invisible; the same knot in a handrail is a splinter factory.
Is Pressure Treated Wood Good for Decks?
Yes, with honest tradeoffs. It has stayed the most-built decking in America for reasons that hold up. Still, it loses to other materials in specific, predictable ways.
Where treated wood wins: it has the lowest upfront cost of any decking and structural strength that composites do not attempt. In fact, even composite decks ride on treated frames. Repairs stay easy because any lumberyard stocks it. And you get real wood looks, plus the freedom to stain any color you want.
Where it costs you later: it is not maintenance-free. Expect cleaning and re-staining on a cycle, plus boards that can check, cup, or splinter as they dry. Above all, the lifespan of the walking surface depends on how faithfully you maintain it. A treated frame reliably outlives its first set of deck boards.
If the maintenance cycle is the dealbreaker, start with our wood vs composite decking guide for Georgia.
Even Composite Decks Are Pressure Treated Underneath
Here is the part of the lumber aisle most homeowners never think about. Choosing composite decking does not remove treated wood from your project. Nearly every composite surface rides on pressure treated pine posts, beams, and joists. Therefore, the use categories and hardware rules in this guide apply to every deck we build, whatever the surface.
Two framing rules protect that investment. First, spec the right category per location. Use ground contact for posts and anything near grade, and above ground for elevated framing with airflow. Second, match the hardware to the chemistry. Modern copper-based preservatives are more corrosive to plain steel than the old formulas. Consequently, structural connections call for hot-dip galvanized or stainless fasteners and connectors. Bright screws from the junk drawer will corrode at the shank. After all, a deck is only as strong as its connections. Corroded fasteners and soft posts are two of the most common findings on our deck repair calls. Both trace back to this section.
When to Stain Pressure Treated Wood
This is the most-asked treated-wood question we get, and the answer decides whether your finish bonds or peels. Standard treated lumber arrives saturated from the treatment process. Stain applied over that trapped moisture cannot penetrate, and it fails fast.
The rule: let the wood dry first, then stain. Drying time runs from several weeks to a few months depending on the season, board thickness, and Georgia humidity. For example, lumber bought in a wet spring dries slower than boards baking through July. Skip the calendar and use the water test instead: sprinkle water on the board. If it beads up, the wood is still too wet and needs more time. If it soaks in within a minute or so, the surface is ready to accept stain.
There are two exceptions to the waiting game. First, KDAT lumber arrives kiln-dried, so you can usually finish it right away. Second, a deck that has grayed through a season needs cleaning and brightening before stain, not more waiting. Would you rather hand this off? Finish timing and application are exactly what our deck staining and painting service exists for.
Pressure Treated vs Cedar
The classic wood-on-wood matchup. Cedar resists decay naturally, weighs less, and carries a color and aroma treated pine cannot fake. Treated pine costs meaningfully less, takes structural duty cedar should not, and handles rated ground contact. Cedar has no answer for that. In Georgia, the practical split is simple. Use treated pine for every structural member and for budget-conscious surfaces. Cedar, meanwhile, serves as the appearance upgrade on boards and rails for owners who accept its softer surface. Termites and humidity make untreated anything a short story here.
What Pressure Treated Wood Costs
Treated pine is the least expensive way to build a deck, full stop. Moreover, that advantage is largest on big, simple layouts. The honest accounting runs over years, not at the register. Add the recurring cost of cleaners and stain, and the gap against composite narrows with every cycle. Lumber pricing also moves with the commodity market, so quotes age quickly. For a current number on your square footage and height, run the deck cost calculator. Afterward, we will sharpen it on-site.
Pressure Treated Wood Questions We Hear Weekly
Do you have to use ground contact lumber for deck joists?
Not in most cases. Above-ground (UC3B) joists and beams remain code-compliant when they sit well above grade with ventilation. Some exceptions call for ground contact ratings, though. These include framing within 6 inches of soil, debris traps, poor airflow under low decks, and hard-to-replace members. Posts and anything touching soil or concrete are always ground contact.
Why is pressure treated wood green?
That tint is the copper in the preservative reacting with the wood. It is normal and varies board to board. Over time, it fades toward brown and gray as the lumber weathers.
Is pressure treated wood safe for families and pets?
Today’s residential lumber uses copper-based preservatives; the arsenic-era CCA formula left the residential market in 2004. Standard practice still applies: do not burn treated scraps, and wash up after cutting it.
Can you build a deck with untreated wood?
Not one you want to keep. In Georgia’s humidity and termite pressure, untreated pine in exterior service decays in a few short years. Treatment, or a naturally durable species, is not optional here.
What screws do you use with pressure treated wood?
Hot-dip galvanized or stainless steel for anything structural, and hardware rated for treated lumber on every hanger and connector. Modern copper-based treatments corrode plain and lightly coated steel, and fastener failure is a structural failure. Our Georgia deck building codes guide covers the connection requirements inspectors actually check.
How long does pressure treated wood last on a deck?
The frame, correctly specified and kept ventilated, serves for decades and routinely outlives the surface above it. Deck boards are the maintenance-dependent part. Cleaned and re-stained on schedule, they give long service. Neglected, they check, cup, and gray their way to early replacement.
Build It Right the First Time
The material is honest: treated pine will give you exactly as much deck as the specification and the maintenance behind it. Getting the use categories, grades, hardware, and finish timing right on day one is the whole game. Fortunately, that is the part we handle for you. Whether you want a new custom wood deck or a frame-up rescue, reach out for your free on-site consultation. Then we will spec it board by board. Finally, for deeper reference on treatment standards, the industry’s own treated wood FAQ is where we point detail-hungry homeowners.