Cedar vs. Pressure-Treated vs. Black Locust: What Lasts in a New England Yard

Every project starts with the same question, usually asked a little sheepishly: "What wood should this be?"

There's no shame in it. It's the most important decision on the whole job, and the marketing around outdoor lumber doesn't help. Here's how we think about the three woods we actually build with.

Pressure-treated pine

This is the green-tinted lumber stacked outside every hardware store. It's southern yellow pine soaked under pressure with a copper-based preservative, which is what keeps it from rotting.

Where it's good: Cost. It's the cheapest option by a wide margin, and for posts going into the ground it's rated for decades of contact with soil. If the structure is going to be painted or hidden, it's a reasonable choice.

Where it isn't: It arrives wet from the treatment and dries in your yard, which means it twists, checks, and shrinks over the first year. Joints that were tight in the shop loosen. The green fades to a dull gray that doesn't age the way cedar does. The treatment also corrodes ordinary screws and hinges, so everything has to be stainless or hot-dip galvanized. And for raised beds, a lot of people just don't want treated lumber next to the tomatoes. Modern treatments are considered safe for that, but we understand not wanting to think about it.

Our take: Fine for posts and framing that won't be seen. Not what we'd choose for a gate or an arbor you look at every day.

Cedar

Our default, and what most of our pieces are built from. We use Northern White cedar.

Where it's good: It resists rot and insects on its own, no treatment needed. It's light, stable, and dries without the twisting you get from pine. Left alone it weathers to a soft silver-gray; oiled or stained it holds a warm honey color. It takes joinery well, which matters when you're cutting real joints instead of driving screws.

Where it isn't: It's soft. A cedar gate that gets kicked shut every day will show it. It costs more than treated pine, and cedar in ground contact won't last as long as treated posts will. For anything going into the dirt, we either set cedar posts on steel bases above grade or use a different wood for the buried part.

Our take: The best balance of longevity, looks, and cost for almost everything we build. Fifteen to twenty-five years above ground with basic care is realistic here.

Black locust

The wood people haven't heard of until they've had a fence post rot out twice.

Where it's good: Black locust is the most rot-resistant wood that grows in this part of the country. Farmers have used it for fence posts for two centuries because an untreated locust post in the ground outlasts most treated ones. It's extremely hard and heavy, so a locust gate or bed doesn't dent or wear.

Where it isn't: It's hard to work. It dulls blades, it's tough to drive fasteners into without pre-drilling, and it's heavy enough that a large structure needs planning to move and install. Supply is limited in Massachusetts, so lead times are longer and the cost is the highest of the three. It also checks as it dries, which some people love and some don't.

Our take: The right answer for anything in permanent ground contact, and for raised beds where you want the last set you'll ever build. Overkill for a trellis.

What we'd tell a friend

Cedar above ground, locust or treated pine in it, and don't let anyone talk you into treated lumber for a piece you'll look at every day. If you're not sure which one your project calls for, tell us what it is and where it's going. That's usually enough for us to say. Start a Project!