When building outdoor structures like decks, fences, gazebos and other landscape features, choosing the right materials is key to creating a beautiful and durable project. Two of the most popular wood options for outdoor building are treated lumber and cedar. But how do you decide which is best for your project? Treated lumber and cedar have unique properties that make them suitable for exterior use.
What Makes Treated Lumber and Cedar Unique?
Before diving into the details, it’s helpful to understand what makes these two wood types different.
Treated Lumber
Treated lumber refers to wood that has been pressure-treated with chemical preservatives. This process forces special preservative deep into the wood to help resist rot, fungal decay and insect damage.
The most common preservative used today is alkaline copper quaternary (ACQ). This has replaced more toxic treatments like chromated copper arsenate (CCA) and ammoniacal copper zinc arsenate (ACZA). ACQ contains copper and quaternary ammonium, allowing for effective treatment without the use of arsenic.
Treated wood is easily identifiable by the greenish tint and the hundreds of small incisions left in the wood from the treatment process.
Cedar
Cedar is a naturally rot-resistant wood that contains natural oils that act as preservatives. This gives it excellent resistance to moisture damage, decay and insect infestation.
Its natural oils also provide an attractive reddish-brown color and distinctive aroma. Cedar is sourced from several varieties of trees, including Western red cedar and Northern white cedar. It is lightweight, easy to work with, accepts stains, and finishes well.
Now that we’ve covered the basics, let’s compare treated lumber and cedar for outdoor projects.
Treated Lumber: The Pros and Cons
Let’s start by looking at the benefits and drawbacks of using pressure-treated lumber.
Strength and Durability
One of the primary advantages of treated wood is its exceptional strength and durability. The pressure treatment process forces preservatives deep into the cellular structure of the wood, protecting it from rot and fungal decay.
Treated lumber is highly resistant to moisture, rain, snow and humidity damage. This makes it an ideal building material for outdoor projects where wood will be exposed to the elements.
The preservatives also provide effective protection against wood-boring insects like termites and carpenter ants. This resistance to insect damage enables treated lumber to last for decades, even with ground contact.
Because of its durability and resistance to nature’s elements, treated lumber is commonly used for structural components like:
- Deck posts, beams and joists
- Fence posts and rails
- Retaining wall structural members
- Porch and pergola posts and framing
- Raised garden bed frames
The exceptional strength and weather-resistance of treated lumber make it well-suited for these critical structural parts of outdoor projects.
Aesthetic Limitations
While treated wood is praised for its strength and resilience, it has some limitations regarding aesthetics.
The pressure-treating process leaves numerous surface incisions, interrupting the wood grain’s smooth, natural look. This gives treated lumber a rough, almost porous appearance that some find unappealing.
Over time, untreated treated wood will weather to a faded greyish-brown color as sunlight wears away the surface fibers. While some may like this weathered, rustic look, it lacks the rich color tones of many other wood types.
Treated lumber is also very difficult to stain effectively. The preservatives obstruct absorption and adhesion of stains and finishes. When stained, treated wood lacks the depth of color and luster of smoother woods like cedar or redwood.
If aesthetics are important for your project, treated lumber may not be ideal for visible surfaces like deck boards, railings, benches or ornamental elements. The incisions and color limitations may be undesirable for wood that will be prominently displayed.
Maintenance
Properly maintained treated lumber can last upwards of 20-30 years. However, it requires routine care and re-treatment to maximize its lifespan.
It’s important to allow treated wood to fully dry after installation before applying any stains or water-repellent finishes. The moisture content must be below 15% – drying time depends on the climate but can take several weeks.
When ready to finish, transparent stains or sealers are recommended. These will help limit moisture absorption while allowing the wood’s natural weathering. Refinishing every 2-3 years will maintain protection.
For optimal durability, treated lumber should be re-treated with a copper-based preservative every 4 to 6 years. This will replenish the protective chemicals within the wood.
Warping and checking can be minimized by sealing the ends and finish-cutting treated wood as soon as possible after installation. Leaving the ends unsealed will allow moisture intrusion and accelerate deterioration.
While treated lumber is long-lasting, it requires simple maintenance to maximize its performance and longevity.
Health and Safety
Today’s treated lumber utilizes much safer chemicals than in the past, but it’s still important to take precautions when working with pressure-treated wood:
- Wear gloves, long sleeves and pants when handling and cutting to minimize skin exposure to preservatives. Also wear eye and lung protection.
- Clean sawdust and debris thoroughly after construction.
- Do not burn treated wood; toxic chemicals may be released as ash. Dispose of at approved solid waste sites.
- Wash hands and clothes after working with treated lumber to avoid ingesting preservatives.
- Avoid using treated wood where it will directly contact food during vegetable gardening or grilling. Use untreated wood or a protective barrier instead.
While modern treated lumber is considered safe for approved residential uses, following basic safety precautions during construction and disposal is smart. Consulting a local building expert is advised if you have any concerns about its use for a particular project.
Cedar: The Pros and Cons
Now let’s examine cedar’s unique benefits and limitations for outdoor structures.
Aesthetic Appeal
One of the primary advantages of using cedar is its inherent beauty. The rich, warm hues and tight grain patterns of cedar make for an attractive finish in outdoor structures.
Cedar’s natural oils help resist UV damage from sunlight, slowing the greying process and maintaining its reddish-brown color longer than many woods. This allows the beauty of cedar to persist for years.
The fine grain and relatively smooth face of cedar also accept stains very well. Cedar can be easily stained in semi-transparent or solid colors to complement your exterior finishes. Staining also enhances cedar’s natural resistance to moisture and UV rays.
Unlike treated lumber, cedar does not have incisions marring the surface. This smooth grain makes cedar more visually appealing for prominent outdoor surfaces like deck boards, handrails, benches, fencing and timber framing accents.
If creating an outdoor space with eye-catching woodwork is your goal, few woods surpass cedar in terms of longevity and natural attractiveness.
Natural Resistance
In addition to its coveted appearance, cedar naturally resists rot, fungal decay and insect damage. The natural oils contain compounds called thujaplicins that act as natural preservatives.
This gives cedar durable resistance to moisture, humidity, rain, snow and other outdoor exposure without chemical treatment. It properly maintained cedar ranks among the longest-lasting woods for exterior use.
Cedar’s natural durability comes from a few factors:
- Dense grain – The tightly-packed grain structure limits moisture penetration into the wood.
- Water-repellent oils – Natural oils make the wood resistant to absorbing and retaining water.
- Rot-inhibiting compounds – Thujaplicins and other substances fight fungal growth and decay.
- Unappealing aroma – The strong scent of cedar oil deters wood-boring insects.
While not as rot-resistant as old-growth Heartwood, cedar offers moderately good longevity even with direct ground contact. Its natural durability makes cedar suitable for various outdoor applications, both structural and aesthetic.
Maintenance
One of the maintenance advantages of cedar is that it takes stains, paints and finishes very well. Cedar’s smooth face provides good absorption and adhesion for coatings.
A penetrating oil-based stain is highly recommended every 2-3 years to enhance cedar’s weather resistance and maintain its rich coloration. The finish soaks into the wood grain without forming a film or plastic-like coating.
If you prefer a colored opaque finish, high-quality acrylic or oil-based paints are also suitable for cedar. These form a protective film layer on the wood’s surface but require more frequent reapplication than penetrating stains.
Use a tinted transparent stain or clear wood preservative to retain cedar’s natural hues. Make sure any finish offers UV protection to prevent grey tones over time.
Proper surface preparation is key before applying any stain or finish to cedar. The wood surface must be clean and dry before coating. Lightly sanding also promotes better finish adhesion.
Cedar’s open and porous nature means it can easily soak up water if untreated. Regular finish reapplication prevents moisture intrusion and surface mildew or molds.
While cedar requires refinishing more often than treated lumber, its ability to take coatings well makes maintenance relatively straightforward.
Limitations
Despite its strengths, cedar does have some inherent limitations to consider:
- Limited structural strength – Cedar has less span capacity than denser woods and treated lumber. Supports and framing need to be beefed up for maximum rigidity.
- Not recommended for ground contact – Cedar has only moderate rot-resistance with direct ground contact. Elevate above soil or use treated wood components instead.
- Prone to splitting – Cedar shakes and shingles are prone to cracking and splitting as they age, requiring replacement every 10-15 years.
- Soft surface – The low density of cedar makes it more prone to dents and abrasions if left unprotected on horizontal surfaces like decks.
- Cost – Cedar is more expensive than pressure-treated lumber and other common decking woods. The added beauty and durability comes with a higher price tag.
Cedar works well for many exterior applications, but it’s smart to avoid spanning long distances and direct ground contact situations. Routine maintenance and protective finishes are key for maximum performance.
Comparative Analysis
Now that we’ve covered the pros and cons of each wood type, let’s directly compare the key factors you’ll want to consider when choosing between treated lumber and cedar:
| Factor | Treated Lumber | Cedar | Winner |
| Durability | Exceptional durability, can last over 30 years if maintained. | Natural rot-resistance but generally lasts 15-25 years. | Treated Lumber |
| Aesthetic Appeal | Limited staining capabilities, fades to grey over time. | Fine grain, warm tones, takes stains well. | Cedar |
| Maintenance | Requires periodic re-treatment and refinishing. | Needs reapplication of finishes every 2-3 years. | Toss-up |
| Cost | More affordable, especially for structural components. | More expensive, especially higher-quality grades. | Treated Lumber |
| Environmental Concerns | Uses safer chemicals but still raises some environmental concerns. | More environmentally friendly due to its natural properties. | Cedar |
Durability
Treated lumber offers exceptional durability and longevity thanks to its chemical preservation. It can last over 30 years if properly maintained.
Cedar has natural rot-resistance but not considered as long-lasting as treated lumber. Finishing and avoiding ground contact maximizes its 15-25 year lifespan.
Winner: Treated lumber is the longer-lasting choice, especially in structural applications.
Aesthetic Appeal
Treated lumber has a rough, incision-filled appearance and limited staining capabilities. Fades to a grey, weathered color over time.
Cedar offers a fine grain and warm, attractive tones. It takes stains and paints well to enhance its beauty. Maintains color longer than most woods.
Winner: Cedar is the superior choice for visual appeal and customizable finishes.
Maintenance
Treated lumber needs periodic re-treatment and refinishing for maximum durability and protection. Allow to dry before finishing.
Cedar accepts stains and paints well but needs reapplication every 2-3 years for ideal protection and aesthetics.
Winner: Toss-up. Both require refinishing and re-treatment to prolong their lifespan. Cedar needs more frequent maintenance.
Cost
Treated lumber is one of the most affordable pressure-treated woods. Significantly lower cost than most other decking/fencing options.
Cedar has a moderate to high cost, depending on grade. Higher-quality Heartwood is expensive. Prices can be 20-45% higher than treated lumber.
Winner: Treated lumber is the budget-friendly choice. Cedar carries a cost premium.
Environmental Considerations
Treated lumber uses safer chemicals today but some may still have environmental concerns about preservatives, disposal and safety.
Cedar earns eco-points for being natural and renewable. Responsible harvesting and milling have lower environmental impacts.
Winner: Cedar is the more environmentally-friendly decking choice. Treatments make treated lumber less green.
Cost Factor
Let’s explore cost considerations in more detail, since price is often the deciding factor for many homeowners and DIYers.
On average, cedar decking will cost 20-45% more than comparable ACQ pressure-treated lumber. Here are some ballpark figures based on material costs only:
- Pressure-treated deck boards – $1.50 – $3.00 per square foot
- Cedar deck boards (5/4″ thick) – $3.00 – $5.50 per square foot
- Cedar deck boards (4/4″ thick) – $2.00 – $4.00 per square foot
- Pressure-treated posts/beams – $5 – $15 each
- Cedar posts/beams – $25 – $60 each
Cedar is more expensive for a few understandable reasons:
- Native cedar trees take decades to mature fully. Responsible harvest rotation times impact supply.
- Milling waste is very high, up to 50% in some cases. More raw material input is needed.
- As a premium wood, demand drives up costs and cedar often has price inflation.
- There are higher processing inputs to mill and treat cedar for decking use.
However, cedar advocates argue the up-front cost is compensated for by its enhanced aesthetics, lower maintenance and increased lifespan. The value derived from cedar’s beauty and performance may justify the initial investment for the right projects.
Both options provide lasting value. It’s about aligning your choice with your specific project requirements and budget.
Use Cases: Where Each Wood Type Shines
Now that we’ve compared the pros, cons and costs, let’s look at ideal use cases where treated lumber and cedar each excel:
Treated Lumber Works Best For:
- Structural framing – posts, beams, joists, knee braces
- Deck and porch substructures and underpinnings
- Exterior steps and stair stringers
- Direct ground contact – fence posts, retaining walls
- Hidden foundation elements and ledgers
- Garden beds and planter boxes
- High traffic decking in dry climates
Treated lumber is unbeatable where structural strength, ground contact and moisture resistance are vital. It also makes economical sense for hidden structural elements.
Cedar is Ideal For:
- Deck boards and railings
- Porch decking
- Timber framing accents and ornamentation
- Fencing, gates and trellises
- Retaining wall facings
- Planter boxes and raised beds
- Exterior siding and architectural details
- Outdoor furniture like benches, tables, raised beds
Cedar brings beauty and natural elegance to any exterior wood that will be prominently visible. It’s worth investing in surfaces where you’ll appreciate its appearance and craftsmanship.
Final Thoughts
There’s no universally “correct” option when choosing between pressure-treated lumber and cedar. The right material depends on the specific needs of your outdoor project. Treated lumber makes sense for structural integrity, spans, wet climates, and ground contact. Its affordability also appeals to many DIYers and budget-conscious builds. Just don’t expect much aesthetic charm.
For elevated surfaces where beauty matters most, cedar is worth the extra cost. Its fine grain, warm hues and staining potential create show-stopping deck boards, railings, fencing and accents. Whichever material you choose, following best practices for installation, care and maintenance will ensure it lasts for decades. Proper planning and construction allow you to build a durable, gorgeous outdoor living space with treated lumber or cedar.
Now that you know the comparative benefits and limitations, you can choose between treated lumber and cedar for your next exterior woodworking adventure.
