Redwood has been a preferred exterior building material in the United States for more than a century. The grading rules that describe it were developed and maintained by industry associations over that same period, giving lumber suppliers, landscape architects, contractors, and homeowners a shared vocabulary for specifying quality. Trade associations continue to shape how materials reach the market, whether the product is redwood lumber or newer systems such as insulating concrete forms. For builders, the payoff is a material with documented grades, predictable working properties, and a long service record in outdoor applications ranging from decks and fences to siding and structural framing. Redwood’s combination of natural durability, dimensional stability, and easy workability explains why it remains a staple for landscape projects, retaining walls, planters, and pergolas as well.
How Redwood Grades Are Organized
Redwood is sorted into six standard grades that balance appearance, strength, and cost. The top grades contain mostly heartwood with few defects, while the economy grades permit knots and other characteristics. Grade selection drives both the look of the finished project and the budget, so matching the grade to the application matters from the start. Redwood demand also tracks the pace of development, and building approvals and entitlement timelines shape how many projects move forward in a given year, which in turn determines what lumber yards stock and which grades buyers can get on short notice.
Heartwood Versus Sapwood
The most important distinction in redwood grading is heartwood versus sapwood. Heartwood contains extractives that resist decay and insects, while sapwood is the lighter outer band of the tree that lacks those protections. Clear All Heart and Construction Heart specify heartwood only, making them the right choices for ground contact and damp conditions. Construction Common and Merchantable grades allow sapwood, which lowers cost for fencing, planters, and utility applications. For a project where boards sit close to soil, such as raised beds or retaining walls, the price premium for heartwood buys real service life; for vertical siding above grade, a mixed grade often performs well for decades.
| Grade | Heartwood | Allowed Defects | Typical Use |
|---|---|---|---|
| Clear All Heart | All | None | Decks, siding, trim |
| Clear | Mostly | Minor | Fascia, railings |
| B Grade | Mixed | Small knots | Paneling, cabinets |
| Construction Heart | All | Tight knots | Structural, ground contact |
| Construction Common | Mixed | Knots and checks | Fencing, planters |
| Merchantable | Variable | Larger knots | Utility framing |
Reading a Grade Stamp
Information on the Stamp
Every certified board carries a stamp with the mill number, grade, moisture content at surfacing, and species code. Checking the stamp takes seconds and prevents substitution of a lower grade at delivery. Look for the WWPA or similar grading agency mark, the mill identifier, and the moisture designation such as S-DRY for 15 percent or less. A board stamped S-GRN has not been dried to the same standard and will move more after installation.
Working Properties on the Job Site
Redwood is lightweight but strong, which keeps handling costs down and makes installation straightforward. A dried board weighs roughly 25 to 28 pounds per cubic foot, light enough for one worker to manage long lengths without mechanical lifting. It nails, saws, and drills cleanly without excessive splitting, and it holds fasteners well in most applications. New homeowner protections in California have raised expectations for durable, low-maintenance exterior materials, and redwood’s refinishing record fits that pattern.
Cutting, Fastening, and Coating
Field crews appreciate that redwood accepts both nails and screws without pre-drilling in most cases, and pneumatic fasteners drive cleanly at the surface. It also ranks among the best softwoods for holding stains, paints, and clear finishes, and surfaces can be restored repeatedly with minimal cost and effort. A weathered deck can be cleaned, sanded, and refinished rather than replaced. Dimensional stability matters here as well: redwood shrinks and swells less than many other softwoods, so joints stay tight, boards stay flat, and coatings do not crack along grain lines as quickly.
- Lightweight at roughly 25 to 28 pounds per cubic foot when dry
- Nails, saws, and drills cleanly without excessive splitting
- Holds paints, stains, and clear coatings well
- Can be refinished multiple times over its service life
Durability, Decay Resistance, and Fire Performance
Heartwood redwood resists decay and insects naturally, without pressure treatment or chemical additives. That durability is the reason redwood appears in decks, fences, and siding in wet coastal climates, and it is one of the few softwoods that performs well in ground contact when the right grade is specified.
Why Heartwood Resists Decay
The extractives that give redwood its color are the same compounds that deter fungi and insects. Because these protectants are concentrated in heartwood, grade choice directly controls durability. A deck built from Construction Heart will outlast one built from Merchantable in the same exposure, which is why specifying the grade matters as much as choosing the species. Environmental rules have also reshaped material selection, much as efficiency regulations changed lighting standards. Redwood’s renewable sourcing and long service life compare favorably to products with higher embodied energy.
Fire Performance
California redwood also meets strict fire codes. Large-dimension members char slowly when exposed to flame, and the char layer insulates the wood beneath it, buying time during a wildfire event. Deck boards and siding behave differently than heavy timbers, so local fire requirements still govern thickness, spacing, and assembly details. In wildfire-prone areas, designers pair redwood with noncombustible fasteners, metal flashing at deck-to-wall connections, and ember-resistant under-deck enclosures to satisfy both structural and fire separation rules.
Redwood Versus Composite Decking
Composite decking dominates marketing budgets, but redwood holds real advantages. Redwood is naturally resistant to decay and insects, while composite boards rely on plastic binders and still show wear at cut edges and fastener holes. Redwood can be sanded and refinished; composite boards must be replaced when damaged. Composite also expands more with heat, which forces designers to plan wider gaps and specific fastener patterns, while redwood behaves predictably across the same temperature swings.
Cost and Maintenance Over Time
The comparison changes when maintenance is priced in. Redwood needs periodic cleaning and refinishing, while composite decks require occasional washing and little else. Composite boards carry warranties of 25 to 30 years, but redwood installed from heartwood grades has a field record that stretches back decades longer.
| Factor | Redwood | Composite Decking |
|---|---|---|
| Upfront cost | Moderate | Higher |
| Maintenance | Periodic refinishing | Occasional washing |
| Repair | Sand and refinish | Replace boards |
| Lifespan with care | Decades | Warranty dependent |
| End of life | Biodegradable | Landfill or recycle |
Redwood adapts to a wide range of climates, from foggy coastal towns to desert settings where outdoor living runs year-round, and its dimensional stability keeps boards flat through seasonal humidity swings. A maintenance schedule for a redwood deck is straightforward: sweep debris, wash with a mild deck cleaner once a year, and reapply a water-repellent finish every two to three seasons depending on sun exposure. Because the wood sands cleanly, a badly weathered board can be brought back with a light pass instead of being ripped out.
Sourcing, Codes, and Specification
Specifying redwood starts with the grade and ends with the supplier. Mills that participate in third-party grading programs certify moisture content and grade, and distributors stock the common grades in volume. California redwood comes from managed forests, and buyers can request documentation of the harvest source. Contractors who track code changes can plan redwood specifications around shifting requirements instead of reacting to them at the last minute.
Specification Checklist
- Confirm the exposure class: ground contact, above ground, or interior.
- Select the grade that matches appearance and durability needs.
- Specify heartwood for damp locations and ground contact.
- Verify the grade stamp and moisture content at delivery.
- Order from a supplier that documents the source and grading.
Moisture Content and Handling
Storage on Site
Store redwood bundles off the ground on stickers, keep them covered, and allow boards to acclimate before installation. End sealant on freshly cut pieces reduces checking, and fasteners should be hot-dipped galvanized or stainless in coastal and treated-wood contact. Delivery inspection is part of the job: reject bundles with excessive twist, wane, or splits beyond the grade allowance, and keep a copy of the mill invoice so any claim can be traced back to the source.
Redwood’s combination of natural durability, dimensional stability, and easy workability keeps it in the rotation for exterior construction. Builders who understand the grade system, match the grade to the exposure, and verify what arrives on the truck get predictable performance for decades. Construction laws continue to raise the bar for durable materials, and redwood’s century-long record gives specifiers confidence that the material will keep meeting those standards.