Cedar vs Douglas Fir: Weight, Cost & Durability

I Spent Way Too Long Picking Between These Two Woods

I was standing in the lumber yard last spring, staring at two stacks of boards — one cedar, one Douglas fir — and I honestly couldn't remember which one was heavier, which one lasted longer outside, or which one was going to cost me less per board foot. I had my phone out trying to Google it and getting these massive forestry PDFs that didn't answer my actual question. So I did what I always do: I bought both, brought them home, weighed them, priced them out, and built stuff with them. And now I'm going to save you the trouble.

The short version? They're both great woods. But they're great at different things, and picking the wrong one for your project is like wearing hiking boots to the beach — technically fine, but you're making life harder than it needs to be.

The Numbers Side by Side

Here's the comparison table I wish someone had handed me before I started my deck project. These are based on what I've actually seen at lumber yards and what I've measured myself, so your local prices might vary a bit — but the ratios stay pretty consistent.

That weight difference is the thing that surprised me most. Douglas fir is roughly 48% heavier than cedar, board for board. If you're building something you have to carry up a ladder or mount overhead — like soffit panels or a pergola — that adds up fast.

So why does Douglas fir cost less if it's denser and harder? Basically it comes down to supply. Douglas fir grows faster, grows in more places, and gets harvested in absolutely massive quantities for construction framing. Cedar is more of a specialty wood, especially the clear grades.

Weight Matters More Than You Think

I built a fence last year — about 120 linear feet — and I priced it out in both woods. The cedar boards I was looking at weighed about 1.4 lbs per linear foot for a standard 1x6, and the Douglas fir equivalent was closer to 2.1 lbs per linear foot. Doesn't sound like much until you multiply it out.

For my fence, using 6-foot-tall boards with pickets every 3.5 inches on center, I needed roughly 410 boards. In cedar, that's about 3,444 lbs of lumber total. In Douglas fir? About 5,166 lbs. That's over 1,700 lbs more wood to haul, lift, and nail. My back is grateful I went with cedar.

If you're trying to figure out weights for your own project, the

Durability — And This Is Where It Gets Interesting

Cedar wins outdoors. That's the bottom line.

Western red cedar has natural oils — thujaplicins, if you want to get nerdy about it — that make it resistant to rot, insects, and fungal decay. I've pulled cedar fence posts out of the ground after 15 years and found them still solid. Not perfect, but solid. Douglas fir in the same situation without pressure treatment? You're looking at maybe 5 to 7 years before it starts getting punky and soft.

But here's the thing — Douglas fir is structurally stronger. Way stronger. Its bending strength is nearly double cedar's, and it holds screws and nails much better because it's denser. So for anything structural — floor joists, rafters, headers, beams — Douglas fir is the obvious pick. Nobody frames a house in cedar (well, almost nobody). For structural calculations, I'd recommend checking the

If you're building a deck and trying to decide, it kind of depends on whether you're willing to maintain it. Cedar decking looks gorgeous for years with just an annual oil treatment. Douglas fir decking needs stain or sealant religiously, or it'll gray out and start checking within a couple seasons. I've seen both done well and both done terribly.

For indoor projects — like shelving or trim — Douglas fir has this beautiful straight grain that takes stain really well, and it's cheaper. Cedar has that amazing smell (which some people are actually sensitive to, so heads up) and works great for closet lining or chest building. The plywood calculator can help if you're mixing sheet goods into your project planning.

So Which One Should You Actually Buy?

I'll make it simple.

Pick cedar if: your project lives outside, you want low maintenance, weight matters (overhead work, fencing, siding), or you're building something decorative where the natural color and grain are part of the appeal. Yes, you'll pay more per board foot — sometimes 40 to 60% more — but you'll probably replace it less often.

Pick Douglas fir if: you need structural strength, you're framing or building load-bearing anything, your project is indoors or will be painted/sealed anyway, or your budget is tight and you're willing to do the maintenance work. It's a workhorse wood for a reason.

And honestly? Most real projects use both. My last deck was Douglas fir for the substructure (joists, posts, ledger board) and cedar for the decking and railings. Best of both worlds. Use the concrete calculator if you're setting posts in footings, and the scientific calculator if you need to work out angles or load math.

One more thing — if you're comparing costs for a big project, don't just look at price per board foot. Factor in how long each wood lasts without treatment, how much sealant or stain you'll need annually, and whether you'll need to replace boards sooner. The salary to hourly converter is oddly useful here if you want to figure out what your own labor time is worth when calculating the "true" cost of maintenance over 10 years.