Cedar vs Pressure Treated Fence: Which Is Better?

For most Pennsylvania yards, the better wood fence uses both: pressure treated posts in the ground and cedar or treated boards above it. In a cedar vs pressure treated fence comparison, treated lumber wins below grade and cedar competes on looks above it. USDA Forest Service researchers, writing with University of Wisconsin Extension, advise using posts with an in-depth preservative treatment, "preferably a pressure treatment for below ground use," for maximum protection against decay and termites.

Cedar's reputation for lasting comes with a condition many buyers never hear. A University of Minnesota Extension bulletin on fence posts states that "heartwood, and not sapwood, accounts for the durability" of northern white cedar, and Michigan State's extension service reported that the sapwood of durable species lasts about as long as ordinary wood under severe exposure. A cedar board with a lot of pale sapwood in it will not perform like the dark heartwood the species is known for. Both bulletins date from the 1950s, and the biology has not changed. This post compares the two materials where it matters: in the ground, above it, at the fasteners and in the finish.

What Is Pressure Treated Wood?

Pressure treated wood is lumber, usually pine, that has had a preservative forced into it under pressure so it resists decay and insects. The treatment is what does the work.

Not all treated lumber is treated to the same level. The American Wood Protection Association sorts it into Use Categories, and the category is printed on the end tag or treatment stamp of each piece:

• UC3B: above ground, exposed, with poor water runoff. Treatment supplier Viance lists fence pickets among the uses for this level.

• UC4A: ground contact, general use.

• UC4B: ground contact, heavy duty.

AWPA's residential guide calls for Use Category 4A or higher for structural posts. That is the tag to look for on fence posts. A post treated only for above-ground use does not belong in the ground.

The preservatives changed about twenty years ago. The U.S. Environmental Protection Agency reports that in December 2003, manufacturers voluntarily discontinued chromated arsenical (CCA) treated wood products for homeowner uses. EPA's list of residential replacements includes ACQ and copper azole.

What Makes Cedar Resist Rot?

Cedar's resistance is natural, and it is not spread evenly through the tree. The heartwood, the darker wood toward the center of the tree, is the part that resists decay. The sapwood, the lighter band near the bark, does not have that protection.

Michigan State's extension service described the gap in a 1956 bulletin on fence posts. It classed northern white cedar heartwood among the durable woods and said it often lasts up to 20 years under severe exposure, while the sapwood of the same species and the heartwood of most other species averaged only about 5 years under the same conditions.

The Forest Service guidance says the same thing in one line: when selecting posts of naturally decay-resistant woods, choose posts with mostly heartwood.

For a fence buyer, that means the grade of cedar matters as much as the word "cedar" on the quote. Ask what species and grade the pickets are and how much sapwood to expect.

Cedar vs Pressure Treated Fence Posts: Which Should Go in the Ground?

Pressure treated, rated for ground contact. The ground line is where a wood fence fails. Soil holds moisture against the post, and the Michigan State bulletin notes that high moisture content often occurs when wood touches the ground or is used within 18 inches of the ground surface.

A UC4A post is treated for that exposure. A cedar post depends entirely on how much heartwood is in it, and you cannot see the center of a post at the lumber yard.

Depth matters as much as material in Western Pennsylvania. Post holes have to reach below the frost line so the ground cannot lift the post in winter. Our post on how deep fence posts should be in PA soil covers that.

The Forest Service guidance adds a point about rails that surprises people: horizontal rails require more protection from decay than vertical boards do. Water sits on a horizontal surface and runs off a vertical one. Treated rails behind cedar pickets are a sensible combination.

Which Is Better for Pickets and Panels?

Above the ground, the choice is closer.

Cedar: a warm red-brown color and a grain most people prefer. Left unfinished, it weathers to gray. Its decay resistance depends on heartwood content.

Pressure treated pine: protected through the treatment regardless of which part of the tree the board came from. It usually starts with a green or brown tint from the preservative and takes stain once it is dry.

Whichever you choose, keep the boards off the soil. The Forest Service guidance is direct about it: "Keep boards off the ground." Pickets that touch dirt or sit in mulch wick water into their end grain no matter what species they are.

For a wider comparison that includes materials with no rot risk at all, see wood vs. vinyl vs. aluminum fencing for PA homeowners.

What Fasteners Does Each Wood Need?

The copper in modern treated lumber is hard on ordinary steel. Simpson Strong-Tie, a fastener and connector manufacturer, recommends stainless steel or copper and silicon bronze fasteners with treated wood that has higher copper retention levels, and it warns that electroplated and mechanically galvanized coatings should not be considered hot-dip galvanized.

Cedar brings a different fastener concern, which is appearance. The Forest Service guidance says to use aluminum or stainless steel nails when a water-repellent or stain finish will be used.

On either wood, the wrong nails show up as black streaks first and loose pickets later. Ask what fasteners are in the quote. Our wood fence installation guide for Pennsylvania homeowners explains the rest of the build.

How Should You Finish and Maintain Each One?

Both woods last longer with a finish that sheds water.

The Forest Service guidance recommends a finish that contains both a water repellent and a wood preservative, and it prefers penetrating, pigmented stains over paints.

On timing, University of Missouri Extension states that wood treated with waterborne preservatives can be painted right after installation, before any weathering occurs, assuming the wood is dry. The key word is dry. Treated lumber can still be wet when it is delivered. Let it dry first, then finish it.

After that, plan to wash the fence and recoat it on the schedule the finish manufacturer recommends. For seasonal upkeep, see how weather in Western PA affects fence materials over time.

Which One Should You Choose?

Choose by where the wood goes and what you want to look at.

• Posts: pressure treated, tagged UC4A or higher.

• Rails: pressure treated, since horizontal members need the most protection.

• Pickets, budget first: pressure treated pine.

• Pickets, appearance first: cedar, with attention to the grade and heartwood content.

Cedar costs more than treated pine for the same footage, so ask for the fence priced both ways on the same layout. If the upkeep of any wood fence sounds like more than you want, read what type of fence is easiest to maintain before deciding.

FAQ

Does cedar last longer than pressure treated wood?

Not in the ground. Treated posts rated for ground contact are the safer choice below grade. Above ground, cedar heartwood holds up well, and its sapwood does not.

Can you mix cedar pickets with pressure treated posts?

Yes, and it is a common way to build a wood fence. It puts treated lumber where the decay risk is highest and cedar where it is seen.

How can I tell whether a post is rated for ground contact?

Read the end tag or treatment stamp. It shows the AWPA Use Category. Look for UC4A or higher on posts.

Is pressure treated wood safe for a backyard fence?

EPA reports that CCA-treated wood was discontinued for homeowner uses in December 2003. Lumber sold for residential fences now uses other preservatives such as ACQ and copper azole.

When can I stain a new pressure treated fence?

Once the wood is dry. University of Missouri Extension notes that waterborne-treated wood can be finished right after installation if it is dry.

Should fence boards touch the ground?

No. Keep them off the ground so the bottom ends can dry.

Wood Fences Built for Western Pennsylvania

Just Fences is a locally owned fence company in Harrison City, established in 2007, that installs wood, vinyl, aluminum, chain link and custom fences for homes and businesses. Free quotes are available, and installations carry a 2-year workmanship warranty. To talk through wood species, post options and styles, start on the custom fences page.

Visit Just Fences or call (724) 392-4416 today. Contact us for more information.