Cedar vs pressure-treated lumber
Cedar is naturally rot-resistant and lighter; treated pine is cheaper and stronger. The part that decides most projects is neither: it is which grade of cedar you are actually being quoted, because "cedar" covers everything from clear heart to construction grade with knots the size of a thumb.
Durability without treatment
Western red cedar heartwood resists decay because of thujaplicins — natural compounds that fungi do not tolerate. The catch is that only the heartwood has them. Sapwood, which is most of a small-diameter tree, has almost none.
That is why grade matters more than species:
- Clear heart — all heartwood, no knots. Highest durability, highest price, often 2× the cost of construction grade.
- STK (select tight knot) — sound knots, mostly heartwood. The usual choice for decking and railing.
- Construction grade — large knots, more sapwood, sold for framing and fencing. Not the same material despite the same species name.
Pressure-treated pine has no such ambiguity: the treatment penetrates the sapwood, which is why it works at all. Ground-contact rated (UC4A or UC4B) treated lumber is rated for burial; above-ground rated (UC3B) is not.
Weight and workability
| Western red cedar | Treated southern yellow pine | |
|---|---|---|
| Density at 12% MC | ~23 lb/ft³ | ~37 lb/ft³ |
| Weight, 2×6 × 12 ft | ~19 lb | ~31 lb |
| Bending strength | Lower | Higher |
| Fastener corrosion | Low (but tannins stain bare steel) | High — requires hot-dip galvanised or stainless |
| Takes stain | Excellent, absorbs evenly | Fair, needs to dry 30–60 days first |
The weight difference is the one people feel immediately. A cedar deck is easier to build alone and easier on the structure, which matters on an elevated deck where the frame is already sized.
Fasteners are not interchangeable
Treated lumber is corrosive to bare steel because of the copper in the preservative. Every fastener, hanger and flashing that touches it must be hot-dip galvanised (ASTM A153), stainless steel, or a coated fastener rated for treated wood. Electro-galvanised and drywall screws will fail in two to five years, and the failure is hidden inside the joint.
Cedar does not corrode fasteners the same way, but its tannins react with bare steel and leave black streaks that are very hard to remove. Stainless or triple-coated deck screws are the practical answer for both materials.
Cost, honestly
For the same nominal size, cedar typically runs 1.5–2.5× the price of treated pine, and clear heart can be 4×. On a 240 sq ft deck that is the difference between roughly $900 and $1,800–2,200 in decking alone.
What you get for it: no chemical treatment to dry out, less weight, better stain absorption, and a surface that does not check and splinter the way treated pine does after a few seasons. What you do not get: more strength, or a longer life against ground contact.
What this comparison leaves out
- It does not cover other species. Cypress, white oak, ipe and cumaru all sit in this conversation; see hardwood decking.
- It does not tell you the grade you were quoted. Ask for the grade in writing — this is where cedar projects go wrong.
- It does not cover finishing schedules. Cedar needs a finish within weeks of installation or it greys; treated pine needs to dry first.
- It does not account for local availability, which in some regions makes cedar cheaper than treated pine.
Questions people actually ask
Is cedar better than pressure-treated wood for a deck?
It is lighter, takes stain better and contains no preservative chemicals, but it is not stronger and construction grade cedar is not more rot-resistant than treated pine. Clear heart cedar is, and it costs roughly twice as much.
Does cedar rot?
Heartwood resists rot; sapwood does not. A cedar board with a large knot and a lot of sapwood will fail at the knot before treated pine fails anywhere.
Can I use regular screws with pressure-treated lumber?
No. The copper in modern treatments corrodes bare and electro-galvanised steel. Use hot-dip galvanised to ASTM A153, stainless, or a coated fastener explicitly rated for treated wood.
How long before I can stain new cedar?
Cedar can be finished almost immediately if it is dry to the touch, though many finishers wait two to four weeks for the mill glaze to weather off. Treated pine needs 30 to 60 days of drying before a penetrating stain will absorb evenly.