What to Know About Buying Wood for Building and Repair Projects

Wood is not all the same, and the type you choose changes what your project costs and how long it lasts

When you walk into a building supply store for wood, you are choosing between softwoods and hardwoods, between pressure-treated lumber and untreated boards, between rough-cut and finished surfaces, and between different grades of the same species. Each choice affects price, durability, appearance, and whether the wood will work for your specific job. A beam that holds up a deck needs different properties than wood for interior trim or a garden bed. Understanding these differences before you buy saves money and prevents having to replace work that fails.

The wood you choose also depends on where you live and how you will use it. South Carolina's heat and humidity mean that some woods rot faster here than in drier climates, and some finishes hold up better than others. Knowing what to look for at the store—and what questions to ask the staff—helps you pick the right material the first time.

Key Takeaways

• Softwoods like pine and fir are cheaper and lighter, while hardwoods like oak and maple cost more but are denser and more durable for visible surfaces.
• Pressure-treated lumber resists rot and insects but contains chemicals, so it should not be used indoors or where food is prepared.
• Wood grading systems (like #1, #2, or Select) describe the number of knots, splits, and defects, which affects both appearance and structural strength.
• Moisture content matters: wood shrinks and warps as it dries, so lumber sold as "green" or freshly cut will change shape over time.
• Dimensional lumber sold as "2x4" or "1x6" is actually smaller than those measurements because of how mills cut and dry the wood.

Softwoods versus hardwoods: what the names mean

Softwoods come from coniferous trees like pine, fir, spruce, and cedar. They are easier to cut and nail, weigh less, and cost significantly less than hardwoods. Most framing lumber, deck boards, and outdoor structures use softwoods because they are affordable and work well for structural jobs where appearance does not matter as much. Pine is the most common softwood at building supply stores in South Carolina.

Hardwoods come from deciduous trees like oak, maple, ash, and walnut. They are denser, harder to cut, more expensive, and more resistant to denting and wear. Hardwoods are used for flooring, fine furniture, cabinetry, and trim where appearance and durability matter. If you are staining or finishing wood to show, hardwood usually looks better and lasts longer than softwood, but you will pay two to four times as much.

The names are misleading: some softwoods (like southern pine) are actually quite hard, and some hardwoods are softer than you might expect. The real difference is that softwoods are faster-growing and cheaper to harvest, while hardwoods take longer to mature and cost more to mill.

Pressure-treated lumber and when to use it

Pressure-treated lumber has been forced full of chemical preservatives under high pressure. These chemicals prevent rot, decay, and insect damage, which is why pressure-treated wood lasts decades outdoors while untreated wood rots within a few years. Most deck framing, fence posts, and outdoor structures use pressure-treated lumber because the cost difference is small compared to having to rebuild in five years.

Pressure-treated lumber should never be used indoors, in kitchens, or anywhere food is prepared or stored. The chemicals can leach into soil and water, so it should not be used in raised garden beds where you grow vegetables. It is safe for decks, pergolas, fence posts, and other outdoor structures where people will not have direct contact with the treated surface. Wear gloves when cutting pressure-treated wood, and do not burn the scraps in a fireplace or wood stove.

Cedar and redwood are naturally rot-resistant softwoods that cost more than pressure-treated lumber but contain no chemicals. They work well for outdoor projects where you want a natural appearance and do not want to use treated wood. In South Carolina's humid climate, even cedar will eventually rot if left unsealed, so plan to recoat it every few years if you want it to last.

Grading systems and what the numbers mean

Lumber is graded based on the number and size of knots, splits, warping, and other defects. The grading system varies slightly by region and wood species, but common grades for softwood include Select (best appearance, fewest defects), #1 (good structural strength, some visible defects), #2 (acceptable for most framing, more knots and defects), and #3 (lowest grade, used for temporary structures or rough work).

For framing a deck or building a shed, #2 grade softwood is standard and costs less than higher grades. For trim, shelving, or anything visible, Select or #1 grade looks better and has fewer knots. Hardwoods use a different grading system (FAS, Select, #1 Common, #2 Common) based on how much usable wood you can cut from each board after removing defects. Do not assume a lower grade is weak: a #2 pine board is structurally sound for most jobs; the grade mainly describes appearance. If appearance does not matter, buying lower grade saves money.

Moisture content and why wood moves

Wood absorbs and releases water based on humidity and temperature. Green lumber is freshly cut and still wet; it is cheaper but will shrink and warp significantly as it dries. Kiln-dried lumber has been dried in a large oven to a moisture content around 12 percent, which is stable for most indoor uses. Lumber sold as "dry" or "KD" has been kiln-dried.

If you buy green lumber for framing, it will shrink as it dries, which can cause gaps, squeaks, and warping in finished surfaces. For interior trim, flooring, or cabinetry, always use kiln-dried lumber. For outdoor structures like decks and fences, green lumber is acceptable because the wood will move regardless of starting moisture content, and the cost savings are significant. Store lumber in a dry place before installation: wood left in the rain or in a damp garage will absorb moisture and swell, then shrink again when it dries, causing the same problems as green lumber.

Actual sizes versus nominal sizes

A board labeled "2x4" is not actually 2 inches by 4 inches. It is roughly 1.5 inches by 3.5 inches. A "1x6" is actually about 0.75 inches by 5.5 inches. This happened because mills cut lumber slightly larger than the nominal size, then plane it smooth, which removes material. The nominal size is what the board was called when it left the mill; the actual size is what you receive.

This matters when you are planning spacing, calculating how many boards you need, or building something that has to fit a specific opening. Measure the actual board before you cut or install it. For most framing jobs, the small difference does not matter, but for trim or cabinetry, it can throw off your measurements. Ask the staff at your building supply store for the actual dimensions of the boards you are buying if you need precision.

Choosing wood for specific jobs

For outdoor decks and structures, use pressure-treated #2 softwood for framing and green or untreated softwood for visible boards, or use cedar or redwood for a natural look. For interior framing and rough work, #2 softwood is standard and affordable. For trim, shelving, and anything you will stain or paint to show, use Select or #1 grade softwood, or choose hardwood if budget allows and durability matters.

For garden beds and raised planters, use untreated cedar, redwood, or composite materials. Do not use pressure-treated lumber. For concrete forms and temporary structures, rough #3 grade or even salvaged lumber works fine. For fine furniture or cabinetry, hardwood is the standard choice. Ask the staff at your building supply store what wood they recommend for your specific project. They can tell you what holds up in South Carolina's humidity and heat, what is in stock, and what will cost the least for the job you are doing.

Frequently Asked Questions

Why does wood cost more at one store than another?

Price varies based on species, grade, moisture content, and how far the wood traveled to reach the store. A board labeled the same way at two stores may have different actual dimensions or moisture levels. Buying in bulk or during sales can lower the per-board cost. Call ahead to compare prices on the specific grade and species you need.

Can I use indoor wood outside, or outdoor wood inside?

Untreated indoor wood will rot quickly outside. Pressure-treated outdoor wood should not be used indoors because of the chemicals. Cedar and redwood can be used either way. For outdoor use, always choose wood rated for outdoor exposure. For indoor use, choose kiln-dried lumber that will not warp from humidity.

What is the difference between a stud and a board?

A stud is a vertical framing member, usually 2x4 softwood, used in wall framing. A board is a general term for any piece of lumber. Studs are graded for straightness and strength for framing; boards can be any grade and any size. Studs cost slightly more because they are selected for straightness.

How do I know if wood is warped or damaged before I buy it?

Look down the length of the board from one end to see if it bows or twists. Check for large knots, splits, or gouges. Feel for soft spots that might indicate rot or insect damage. Reject boards that are visibly warped or damaged. For pressure-treated lumber, check that the green color is even; discolored spots may indicate uneven treatment.

Do I need to treat or seal untreated wood before using it outside?

Untreated softwood will rot within a few years if left exposed to weather. If you want untreated wood outdoors, apply a water-resistant sealant or stain every one to two years. Cedar and redwood last longer without treatment but still benefit from sealing. Pressure-treated wood does not need sealing for rot protection, though you can stain it for appearance.