Composite vs Pressure-Treated Decking

This is a decision about the deck surface only. The frame underneath is pressure-treated lumber either way, because composite boards carry no structural load — they are a wearing surface fastened to a wood frame. So the real question is narrow: what do you want to walk on, pay for, and maintain for the next twenty years? The honest answer is that composite wins on total cost of ownership for most people who will keep the house, and pressure-treated wins on up-front budget, repairability and bare feet in the sun.

The Short Answer

If you will sell within five years or the deck is small, pressure-treated is usually the rational choice. If you are staying and the deck is large, composite tends to be cheaper by year eight to ten once refinishing labour is counted. The rest of this guide is why.

Up-Front Cost

Composite costs more per square foot, but by less than the sticker suggests once the frame, footings, railing and labour are in the number — those are identical or nearly identical for both.

Two things distort the comparison in the showroom. First, entry-level composite and flagship composite are barely the same product — an uncapped or thinly capped budget line will fade and stain in a way that a premium capped board will not, and it is the budget line that produced composite's bad reputation in the 2000s. Second, the railing is often the bigger cheque than the decking. Composite railing systems can cost more per linear foot than the entire deck surface costs per square foot, and many people who choose composite decking pair it with an aluminium or wood railing for exactly that reason.

What Each Costs to Own for 20 Years

This is where the comparison actually resolves. Take a 320 sq ft deck (16 × 20 ft) and count the whole period, not just day one.

The arithmetic is stark once labour enters. If you hire out refinishing, composite's extra up-front cost is repaid in roughly two to three refinishing cycles — around six to nine years. If you do it yourself, composite never quite pays back in dollars; it pays back in weekends. A refinish is a two-day job on a deck this size, done seven to ten times over twenty years. That is three to four weeks of your life, and it is the honest currency of this decision.

The other half of the truth: most pressure-treated decks do not get refinished on schedule. They get refinished twice, then neglected, and then they look like a neglected deck. If you know yourself well enough to know that is what will happen, price composite against a wood deck that will look tired at year eight, not against a perfectly maintained one.

Lifespan, and What Actually Kills Each One

Both materials outlive their reputations in one dimension and underperform them in another.

Pressure-treated

Pressure-treated pine rarely fails by rotting. Modern treatments are genuinely effective and the wood mills warrant against rot and termite damage for decades. What ends a pressure-treated deck is appearance and comfort: surface checking, splitting around fasteners, cupping, splintering and grey weathering. People replace pressure-treated decking because it has become unpleasant to walk on barefoot and unpleasant to look at, long before the wood is structurally spent. Expect roughly 10 to 20 years of surface life, with the top of that range only achievable with consistent refinishing.

One important distinction: the frame lasts much longer than the deck boards, provided the correct treatment retention was used for the application — ground-contact rated material where it is required, which is most of the framing near or on the ground. It is entirely normal to re-deck a 20-year-old frame.

Composite

Capped composite is a wood-flour-and-polymer core with a hard polymer shell. The cap is what makes modern composite work, and it is also its weakness: damage that breaches the cap exposes the core, which will stain and can grow mould. Deep scratches, gouges from dragged furniture and dog claws cannot be sanded out, because sanding removes the cap.

Expect 25 to 30 years or more of service. What limits it in practice is fading (all composites fade some, most of it in the first year or two), colour mismatch when a damaged board is replaced years later, and the discontinuation of the product line — a very real problem when you need three matching boards in year twelve.

Uncapped composite

Avoid it. First-generation uncapped composite absorbs water, fades badly, stains permanently and grows surface mould in shaded damp areas. It is still sold, it is cheaper, and it is the reason a lot of people think composite decking is bad. If a composite board has no cap or is capped on three sides only, treat the price advantage as an accurate reflection of the product.

Maintenance, Honestly

"Maintenance-free" is marketing. Composite is low-maintenance, not no-maintenance — anything horizontal and outdoors collects pollen, grows algae in shade and needs washing. The genuine difference is that composite maintenance is a hose and a soft brush, and wood maintenance is a two-day project with a pressure washer, a sander and a gallon of stain.

One warning on pressure washing: it is the most common way people damage both materials. Too much pressure fuzzes wood fibres and can erode a composite cap. Use the widest fan tip, keep the wand moving and stay well back, or use a deck cleaner and a brush instead.

Heat Underfoot

This is the factor people discover too late, and it is worth taking seriously if you have children, dogs, or any intention of walking barefoot on a south-facing deck in July.

Composite and PVC run hotter than wood in direct sun. Wood is a poor conductor and its fibrous surface holds less heat; a solid polymer-and-filler board absorbs more and holds it. The difference is real enough to be the deciding factor in hot, sunny climates.

But colour matters more than material. A dark espresso or charcoal composite is dramatically hotter than a light grey or tan one in the same product line — far more than the gap between light composite and wood. If you want composite and you want bare feet, choose a light colour and accept that it will show dirt more.

Practical mitigations: shade the deck (a pergola, an awning, or trees changes everything), choose lighter colours, use outdoor rugs in the traffic paths, and be sceptical of any product marketed as heat-reducing without asking for measured data at a specific colour. Manufacturers publish surface temperature comparisons; read them, but note the conditions they were taken under.

Stiffness, Span and Framing

The single most consequential technical difference: composite decking is less stiff than wood of the same thickness, and it is not a structural material. It carries load only between joists, and it relies entirely on the frame beneath it.

The practical consequences:

• Composite usually needs closer joist spacing than wood decking, and closer again for a diagonal layout, for stair treads, and for some wide-plank profiles. The required spacing is a product-specific number published in the manufacturer's installation instructions — get them before you frame, not after.
• Retrofitting composite onto an old frame framed for wood is a common trap. If the existing joists are spaced wider than the composite requires, you are adding joists or sistering in blocking, and that cost belongs in the comparison.
• Composite is heavier than pressure-treated pine per square foot, which is a consideration on long spans and older frames.
• Composite moves with temperature, not moisture. Wood shrinks and swells across its width as it dries and wets. Composite expands and contracts along its length with temperature, which is why butt-joint gapping is specified against the temperature on installation day.

Fastening Systems

The fastening decision follows from the material more than people expect.

Pressure-treated

Face screws are standard, cheap and fast, and the visible heads are part of the look of a wood deck. The non-negotiable requirement is corrosion resistance: modern ACQ and copper-azole treatments are corrosive to plain and electroplated steel, so use hot-dipped galvanised to G185 or stainless. Wood decks can also take plugged screws or hidden side-mount fasteners if you want a clean field, at a significant cost in time.

Composite

Most composite is sold grooved for hidden clips, which set the gap automatically, allow the board to move lengthwise, and leave no penetration through the cap. That is genuinely the right system for the material, and it is also slower and several times more expensive in fastener cost than face screwing.

If you face-screw composite, use screws made for it — composite-specific screws have a cutting head and thread geometry designed to prevent the mushrooming of material around the head that ordinary wood screws cause. Many manufacturers also require pre-drilling near board ends, and some restrict face screwing entirely on certain profiles.

Both

Never use drywall screws on any deck. They are brittle, not corrosion rated, and their heads snap under a board that wants to move. And on either material, snap chalk lines over the joist centres before fastening — a missed screw is a hole you cannot hide, and on composite you cannot fill it.

What a 25-Year Warranty Actually Covers

Composite is sold on its warranty, so read one before you let it influence the purchase. The pattern is consistent across brands:

• It is a limited warranty, and usually prorated. Full value in the early years, declining to a fraction by the end of the term. The headline number is the length, not the coverage.
• Fade and stain coverage is separate and shorter than the structural warranty, and it is defined against a measured threshold — a specific colour-change value, not "it looks faded to me."
• Material only, in most cases. Some premium lines include limited labour coverage; many do not. Replacing a board on a finished deck is mostly labour, so this matters.
• Conditional on installation per the instructions. Wrong joist spacing, insufficient gapping, unapproved fasteners or ground-contact installation can void it, and the claim process asks about all of them.
• Transferability is limited — often one transfer, sometimes with a shorter term for the second owner.
• Proof of purchase is required years later. Keep the invoice, the product line name and the colour with your house records.
• The company has to still exist. A 25-year warranty is a claim about a corporate future, and the decking industry has consolidated repeatedly.

Pressure-treated has warranties too, and they mislead in the opposite direction. A mill's "lifetime limited warranty" typically covers rot and termite damage only — the failure mode that almost never ends a deck — and explicitly excludes checking, splitting, warping, cupping and appearance, which are precisely the reasons pressure-treated decks get replaced. It also generally covers replacement lumber, not the labour to install it.

The useful way to read both: warranties cover the failure the manufacturer is confident will not happen. Buy the board on its material properties and its track record, and treat the warranty as a tiebreaker.

Which One You Should Actually Buy

Buy pressure-treated if

• The budget is the constraint. A wood deck built well beats a composite deck you cannot afford to finish.
• You will sell within about five years. You will not recover the composite premium.
• The deck is small. The refinishing burden that justifies composite scales with area, and a 100 sq ft landing is an afternoon.
• You are in a hot, sunny climate and the deck is unshaded and used barefoot.
• You want to change the colour later, or want the ability to sand out damage and swap boards cheaply.
• You genuinely enjoy the maintenance. Some people do, and a well-kept wood deck looks better than any composite.

Buy capped composite if

• You are staying in the house and the deck is large. This is the clearest win.
• You do not want to spend a weekend on it every second or third summer, and you know you would not.
• The deck is shaded, north-facing, or damp — where wood weathers fastest and composite's mould resistance is worth the most.
• You will hire out refinishing. That is the line item that makes composite cheaper by year eight or so.
• You want the surface to look about the same in year ten as in year two, with no effort.

Consider PVC if

You need the lowest possible water absorption — a poolside deck, a coastal location, a very damp site — or the lightest weight. PVC has no wood content, so it cannot rot, stain from the inside or grow mould in its core. It costs the most, it can feel more plastic underfoot, and it moves the most with temperature, so gapping and fastening discipline matter more.

One last framing note that saves people money: the frame is pressure-treated in every one of these scenarios, and the frame is where deck safety lives. Ledger attachment, flashing, footings, beam sizing and joist spans are the things that make a deck safe. The board on top is a comfort and maintenance decision, and it should never absorb budget that the structure needs.

Frequently Asked Questions

Is composite decking worth the extra cost?

It depends on how long you are staying and who does the maintenance. If you hire out refinishing, composite's extra up-front cost is typically repaid in two to three refinishing cycles, around six to nine years. If you do it yourself, composite never quite pays back in dollars — it pays back in weekends, roughly seven to ten two-day refinishing jobs over twenty years.

How long does composite decking last compared to wood?

Capped composite typically gives 25 to 30 years or more; pressure-treated pine gives roughly 10 to 20 years of surface life, with the top of that range only reachable with consistent refinishing. Note that pressure-treated decking rarely fails by rotting — it is replaced because it has checked, split, cupped and become splintery.

Does composite decking get hot in the sun?

Yes, noticeably hotter than wood. Wood is a poor conductor with a fibrous surface; a polymer-and-filler board absorbs and holds more heat. But colour matters more than material — a dark charcoal composite is dramatically hotter than a light grey one from the same line. If you want composite and bare feet, choose a light colour and add shade.

Can I put composite decking on an existing wood frame?

Often, but check two things first. The frame must be sound — inspect the ledger, flashing, joist hangers and footings before spending anything on the surface. And the joist spacing must meet the composite manufacturer's requirement, which is frequently closer than what wood decking needed. Adding joists or blocking is a real cost that belongs in the comparison.

What joist spacing does composite decking need?

It is product-specific and published in the manufacturer's installation instructions — composite generally needs closer support than wood decking, and closer again for diagonal layouts, stair treads and some wide-plank profiles. Get the instructions before you frame. Separately, allowable joist spans come from AWC DCA-6, IRC Table R507.5 and your local code, not from a decking brochure.

Can composite decking be sanded or refinished?

No. The cap is a thin hard polymer shell and sanding removes it, exposing the wood-flour core to water and staining. This is the main practical disadvantage of composite: deep scratches, gouges and dragged-furniture damage are permanent, and a replacement board bought years later may not match the faded field.

Do I need to seal or stain composite decking?

No, and doing so generally voids the warranty. Composite still needs washing — anything horizontal and outdoors collects pollen and grows algae in shade — but it needs no film-forming finish. "Maintenance-free" is marketing; "low-maintenance" is accurate.

How often does a pressure-treated deck need staining?

Every two to three years in most climates, more often on a south-facing or heavily used deck. Budget $150 to $300 in materials if you do it yourself, or roughly $2 to $4 per square foot to hire out. Over twenty years that is seven to ten cycles, which is the number that decides the composite comparison.

Is a 25-year composite decking warranty real?

It is real but narrower than it reads. Most are limited and prorated, cover material rather than labour, carry a separate and shorter fade-and-stain term measured against a defined threshold, are conditional on installation exactly per the instructions, allow limited transfer, and require proof of purchase decades later. Keep the invoice, product line and colour with your house records.

What does a pressure-treated lumber warranty cover?

Usually rot and termite damage only, which is the failure mode that almost never ends a deck. Checking, splitting, warping, cupping and appearance — the actual reasons pressure-treated decks get replaced — are typically excluded, and coverage is generally for replacement lumber rather than the labour to install it.

Can I use composite for the deck frame?

No. Standard composite decking is not a structural material and carries load only between joists. The frame — beams, joists, posts and ledger — is pressure-treated lumber under both wood and composite decking. Structural composite framing products do exist but they are a different, engineered category with their own specifications.

What is the difference between capped and uncapped composite?

A cap is a hard polymer shell bonded over the wood-flour core. Uncapped composite absorbs water, fades badly, stains permanently and grows surface mould in damp shade — it is what gave composite its poor early reputation. Buy capped, and prefer fully capped over three-sided capping. The price difference reflects a genuine performance difference.