Wood species set the color and character of a timber frame, and they also decide how easily the timbers are cut, how much they move, how well they hold finish, and what the project costs. Oak, pine, fir, hemlock, and cedar are the species most timber home builders reach for, and each behaves differently in a structure. Moisture content matters as much as species. A freshly sawn oak beam and a kiln-dried fir beam can look similar at delivery yet perform very differently in service. The same moisture discipline that governs a mud flooring installation applies here: substrate condition, moisture, and compatibility decide how the finished assembly behaves for decades.
The Most Common Construction Wood Species
Timber frame suppliers work with a short list of species because each must be strong enough for structural spans, stable enough to resist twisting and checking, and attractive enough to be left exposed. Hardwoods such as oak bring density and dramatic grain, while fir, pine, hemlock, and cedar weigh less, machine faster, and cost less per board foot.
| Species | Janka hardness (lbf) | Decay resistance | Typical use | Relative cost |
|---|---|---|---|---|
| White oak | 1,360 | High | Beams, flooring, joinery | High |
| Red oak | 1,290 | Moderate | Flooring, interior trim | High |
| Douglas fir | 660 | Moderate | Posts, beams, rafters | Medium |
| Southern yellow pine | 690 | Moderate | Framing, heavy timbers | Low |
| Western hemlock | 540 | Low | Interior framing, trim | Low |
| Western red cedar | 350 | High | Exterior cladding, decks | Medium |
Grain, Character, and Clear Grades
Within a species, appearance ranges from knot-studded character grades to clear, straight-grained material. Knots are where branches once grew: tight, sound knots add visual interest and cost little in strength, while large or loose knots can reduce a beam’s load capacity. Clear grades come from the outer, branch-free portion of the log and command a premium for their uninterrupted grain. Sawing direction changes the pattern: plainsawn boards show wide, arched grain, while quartersawn boards show tight, vertical grain lines and shrink less across their width.
Reading the Grade Stamp
Structural timbers carry grade stamps identifying species, grading agency, and grade name, such as No. 1 or Select Structural; many stamps also list the moisture content at grading. A building information model for a timber project should record species, grade, and moisture for every member, because substituting one grade for another without checking design values can leave a beam undersized for its span.
Moisture Content and Wood Movement
Wood is hygroscopic, gaining and losing moisture with the surrounding air, and every change in moisture content moves the piece. Green timbers come fresh from the forest at 30 percent moisture or more, kiln-dried timbers leave the kiln at roughly 18 to 20 percent, and in a heated home wood settles toward an equilibrium moisture content of 6 to 14 percent depending on climate. That final drying is where most movement happens.
Many owners pair the frame with panels from the same species family. Sustainable wood wall panelling suppliers publish moisture and stability data that helps match panels to the frame’s seasonal movement so trim joints and panel seams stay tight.
How Much Will the Wood Move?
Shrinkage is not uniform. From green to oven-dry, most softwoods shrink 4 to 6 percent radially and 6 to 8 percent tangentially, while oaks shrink more, around 4 percent radially and 9 percent tangentially. That difference is why a round log becomes an oval and flatsawn boards cup toward the bark. Framing designs allow for it with gaps at connections, slotted fasteners, and trim details that let wood slide without splitting.
Equilibrium Moisture Content by Climate
Know your regional equilibrium moisture content before ordering timbers. In humid coastal areas it sits near 12 to 14 percent; in arid inland climates it drops to 6 to 8 percent. Timbers delivered wetter than the local equilibrium will check and twist in the first heating season. A field check with a pin-type moisture meter takes minutes:
- Take readings on two faces of each timber, at least 6 inches from the ends.
- Record the highest reading, since end-grain dries fastest and hides the interior condition.
- Compare the readings with the target equilibrium moisture content for your region.
- Reject any timber more than a few points above the target unless the design accounts for the extra movement.
Green, Standing-Dead, Dried, and Reclaimed Timbers
Beyond species, suppliers sort material by how it was seasoned. The four categories are green, standing-dead, air- or kiln-dried, and reclaimed, and each trades cost against stability. The right choice depends on how much movement the design tolerates and when the timbers must be ready.
Procurement strategy ties into the project delivery method you choose, because each timber category shifts schedule, cost, and risk differently between owner and builder. Green timbers can be ordered and cut quickly; dried and reclaimed timbers add months of lead time and a measurable premium.
Green Timber: Lowest Cost, Most Movement
Green timbers are the most economical option because they need no kiln time or yard storage, and they are the easiest for the framer to cut while wet. The trade-off is that all the drying happens inside the finished house, so expect checking, especially in the first winter when the furnace accelerates moisture loss. Structural integrity holds up if the frame is properly planned and built, but the look changes as cracks open and close.
Standing-Dead Timber: Stability at a Premium
Standing-dead timbers come from trees killed by insect infestation, fire, or wind, left to dry while still standing. Pests leave once the tree dies and its food source disappears, so the finished timber is clean. The low moisture content makes it more stable and less prone to checking or twisting than green timber, and because it is less plentiful and usually harvested selectively, it costs more.
Air- and Kiln-Dried Timbers: The Predictable Middle
Large kilns dry timbers over several weeks to about 18 to 20 percent moisture. Air-dried timbers sit in log yards for months to years to reach a similar range. Either route adds cost, but the payoff is a frame that moves far less after assembly and accepts finish sooner.
What Drying Adds to the Budget
Drying adds 15 to 40 percent to timber cost over green material, depending on species, section size, and kiln capacity. Large sections dry slowly and tie up kiln space, which is why heavy beams are often air-dried or sourced green.
Reclaimed Wood: History in the Grain
Reclaimed timbers come from dismantled factories, barns, bridges, and piers, some of them centuries old. Some suppliers dredge rivers and lakes near old sawmill sites to recover old-growth logs that sank on the way to the mill. Decades of seasoning have made this material extremely hard and stable, with tight grain that new-growth wood rarely matches. It is the hardest category to source and process, so expect the highest price and the longest lead times.
| Category | Moisture content | Relative cost | Stability | Availability |
|---|---|---|---|---|
| Green | 30% or more | Lowest | Lowest | Readily available |
| Standing-dead | Low | Premium over green | High | Selective harvest |
| Air- or kiln-dried | 18-20% | Moderate | High | Several weeks to years |
| Reclaimed | Very low | Highest | Highest | Limited, long lead |
Grading, Hardness, and Structural Performance
Species and grade determine the design values an engineer uses to size posts and beams. Softwood grading is done visually or by machine stress rating, which measures each piece’s stiffness and assigns a strength class. Hardwoods used structurally are usually graded by appearance and measured density.
The exterior cladding that protects the frame has its own species logic. Engineered wood siding bonds veneers into stable panels, removing much of the seasonal movement of solid boards while keeping a real wood face. Matching the siding system to the frame’s moisture behavior stops it from fighting the structure behind it.
Hardness Ratings and Wear Resistance
The Janka test measures the force needed to embed a steel ball halfway into a board and predicts how a surface resists dents, foot traffic, and tool impacts. White oak at about 1,360 pounds-force shrugs off daily wear, while cedar at 350 pounds-force dents easily and is reserved for low-wear roles such as siding and ceilings. A floor, stair tread, or workbench top deserves the hardest species the budget allows; a beam, where hardness is irrelevant, does not.
Visual Grading vs Machine Stress Rated Lumber
Visual grading relies on a grader’s assessment of knots, slope of grain, and splits, and it is fast and inexpensive. Machine stress rating runs each board through rollers that measure stiffness and assign design values. For long spans and heavy loads, machine-stress-rated material removes much of the guesswork from the engineer’s calculations.
Matching Species to Roles in the Home
The most cost-effective timber home mixes species by role rather than using one wood everywhere. Exposed members carry the visual load and deserve a straight-grained, stable species; hidden framing can use economical grades; high-wear and high-exposure surfaces need durability that appearance alone cannot provide.
A solid wood entry door is one component where species choice shows up immediately: a door is a large, hinged slab that must stay flat and square through every season while carrying its own weight. Species with low shrinkage and stable grain behave best in this role, and the finish schedule depends on how much the chosen wood moves.
Fastening, Joinery, and Preservative Treatment
Species density changes how joinery is cut and fastened. Dense oak holds a mortise and tenon crisply but dulls bits quickly and can split if fasteners sit too close to edges. Softer fir and pine cut fast and accept pegs easily, but their lower density means connections need more bearing area. Exterior and ground-contact members should be treated or use naturally durable species such as cedar, and steel connectors should match the corrosion environment of the site.
Finishes, Stains, and Maintenance Cycles
Finish performance follows species. Open-pored oaks and dense softwoods absorb penetrating oils evenly, while resinous pines can blotch under stains and may need a sealer coat first. Plan a maintenance cycle for exterior timbers, typically a clean-and-refinish pass every 2 to 4 years, budgeted before the frame goes up.
- Oak: flooring, stair treads, joinery details, heavy-use surfaces.
- Douglas fir: posts, beams, and rafters where strength and appearance meet.
- Southern yellow pine: economical heavy timbers and hidden structural framing.
- Western hemlock: interior trim and paneling with a clean, uniform tone.
- Cedar: exterior siding, decking, and any component exposed to weather.
A timber home performs as a system, and moisture ties every part of it together. The frame’s seasonal movement, the foundation’s capillary action, the cladding’s vapor behavior, and the flexible sewer and sanitary pipes buried in the slab all respond to the same water environment. Choose species and moisture content with that whole-house picture in mind, and the frame you raise will look the same in twenty years as the day the last peg goes in.