How Long Does a Deck Last? Cedar, Pressure-Treated and Composite

Twelve to twenty-five years, most of the time. That is the range across the decks Sungreen has built and rebuilt around Calgary since 1990, and material only explains half of it. The other half comes down to how the deck was built, how it gets maintained, and what a Calgary winter does to whatever sits underneath the boards.

A deck lasts exactly as long as its weakest link, and that is rarely the material everyone blames first. The question comes up on almost every consultation, usually phrased the same way: how many years am I actually getting out of this before I am back here rebuilding? Cedar, pressure-treated, and composite each answer that differently, and the answer changes again once freeze-thaw cycles and a deferred staining schedule enter the picture.

How Long a Deck Lasts by Material in Calgary

Composite runs the longest with the least effort. Twenty to twenty-five years is the realistic window, and that number holds even when maintenance slips for a season or two. No staining, no sanding, no annual repainting. We have composite decks twelve years old on Calgary properties that still look close to new.

Cedar decking sits at fifteen to twenty years, but that number assumes the staining schedule stays on track. Re-stain or reseal every one to two years and cedar decking holds up well against Calgary’s dry summers and wet springs. Skip a couple of seasons in a row and the surface grain opens up, moisture gets in, and the lifespan drops fast.

Pressure-treated wood can match those same numbers when it is well maintained. In practice, maintenance gets deferred more often on pressure-treated decks than on cedar decks, since the material was chosen for its lower upfront cost rather than its finish. Degradation runs faster once that happens, and boards holding moisture through a winter are the most vulnerable to frost damage of the three materials.

Vinyl decking, less common on Sungreen jobs but worth mentioning, tracks close to composite on lifespan since it shares the low-maintenance, no-staining profile, at a similar price point.

What Actually Shortens a Deck’s Life

Moisture is the biggest factor by a wide margin. Boards that stay wet between rains, gaps too tight for airflow, joists sitting in standing water under the deck: all of it accelerates rot regardless of species or treatment. Drainage and airflow underneath matter as much as what happens on the surface.

Installation quality is the second factor, and it is the one homeowners have the least visibility into once the deck is finished. Footings poured to the wrong depth, framing that is not properly squared, fasteners that corrode within a few winters: none of it shows up in year one. It shows up in year eight, as a deck that should have had another decade left instead needs a rebuild.

Sun exposure matters more on wood than most people expect. South-facing decks in Calgary take a beating from UV through long summer days, and unprotected wood greys and checks faster on that exposure than a shaded north side ever will.

Usage plays a role too, though a smaller one. A deck holding a hot tub, heavy planters, or daily high-traffic use ages faster at the stress points than the same deck used mainly for evening dinners.

Why Calgary Winters Are Harder on a Deck Than Most Climates

Freeze-thaw is the local variable that changes every lifespan number above. Calgary does not get one long winter freeze. Chinooks push temperatures well above zero for days at a time, mid-January, then send it back below freezing overnight. Wood and structural connections expand and contract through that cycle repeatedly across a single winter, not once per season the way a colder, steadier climate would put them through it.

Footings poured below the frost line and properly cured hold up fine through this. A shallow footing, or a deck built on blocks sitting on ground that later thaws unevenly, moves instead. Movement at the footings shows up as a deck that feels slightly off, a step that was level in September and is not by April, long before any board looks visibly damaged.

How long a deck lasts here comes down to what happens below the boards, not just what sits on top of them. Boards holding moisture are the ones that suffer most, since that moisture is what freezes and expands inside the wood fibre. Composite and vinyl do not absorb water the same way, which is most of why they hold their lifespan numbers through Calgary winters better than wood does.

Signs a Deck Needs Repair, Not a Full Rebuild

Soft spots underfoot, especially near the ledger board where the deck meets the house, usually mean rot has started at a moisture trap. Caught early, that is a board replacement. Left alone through another winter, it spreads into the joists.

Wobbly railings are a safety issue before they are a cosmetic one. A railing that moves under hand pressure has loose or corroded fasteners, and code height in Calgary runs 36 to 42 inches depending on deck height, so a failing railing is not something to leave for next season.

Cracked, splitting, or badly cupped boards on an otherwise sound frame usually mean a board-level repair, not a rebuild. Sagging across a wider section, or fasteners rusted through at multiple points, points toward the frame itself and a bigger job.

Repair fits isolated damage: a handful of boards, one section of railing, fasteners in one area. Resurfacing, replacing the decking boards while keeping a sound frame, works when the substructure tests solid but the surface has aged out. Full replacement becomes the call once the frame itself has failed structurally, since a new surface on a failing frame costs twice over.

How to Make a Deck Last Longer

Staining or sealing on schedule is the single biggest lever on a wood deck’s lifespan, and it is also the one homeowners skip first when life gets busy.

Cleaning matters more than most people assume, since trapped dirt and pollen hold moisture against the boards even when the deck looks fine from a distance. Wood and composite take different cleaning methods, and using the wrong one on either material does more harm than skipping cleaning altogether.

Sanding restores a weathered wood surface enough to take a new coat properly, rather than sealing over rough, greying wood. Composite should never be sanded. It strips the capping layer that gives the boards their colour and their scratch resistance in the first place.

Keeping the space underneath clear of debris, checking fasteners every spring, and dealing with a soft spot the week it appears rather than the season after: all of it adds years without adding cost.

Composite vs Wood: Which Deck Lasts Longer

Composite, under most conditions. Twenty to twenty-five years with minimal upkeep beats a cedar deck’s fifteen to twenty years on a staining schedule, and it beats pressure-treated by an even wider margin once maintenance inevitably slips somewhere along the way.

The upfront cost gap is real. Composite runs $45 to $70 per square foot installed against $25 to $40 for pressure-treated and $35 to $55 for cedar decking. Run the comparison over twenty years instead of one, though, and composite usually wins on total cost of ownership once staining seasons, sanding weekends, and the occasional board replacement get added into the wood side of the math.

That said, cedar has a following for a reason that has nothing to do with lifespan math. The warm wood look, the way it weathers, the fact that it can be refinished rather than only replaced: homeowners chasing that specific look choose cedar knowing the maintenance trade-off going in, and most do not regret it.

What Gets Built Most, and Where

Bearspaw acreages and inner-city infill lots account for most of the composite going in this year, and the reason is close to the same on both ends: a client planning to sell within five to ten years wants a deck that photographs well without a maintenance list attached. Established communities like Mount Royal and Elbow Park still lean cedar, matched to older character homes where the warm wood tone fits the street better than a synthetic board would.

Pressure-treated stays the default on rental properties and larger commercial platforms, where the owner is weighing build cost over a twenty-year finish. Nothing wrong with that trade-off. It just means the maintenance schedule matters more, since the material was never chosen for its low-upkeep profile in the first place.

Frequently Asked Questions

How long should a wood deck last before replacement?

Fifteen to twenty years for a cedar deck with a staining schedule kept up, sooner for pressure-treated if maintenance gets deferred. An untreated wood deck, no stain or sealant applied at all, degrades much faster. Five to ten years before rot and UV damage force the issue, and Calgary’s freeze-thaw cycle shortens that window further.

What is the 3/4/5 rule for decks?

A framing check, not a lifespan rule. Measure three feet along one side of a corner and four feet along the other, and the diagonal between those two points should read exactly five feet if the corner is square. Builders use it to square deck frames before fastening, and a frame that was never properly squared ages worse, since uneven load distribution stresses fasteners and joints faster than a square one does.

How much does a 20×20 deck cost by material?

Roughly $10,000 to $16,000 in pressure-treated, $14,000 to $22,000 in cedar, and $18,000 to $28,000 in composite, for a 400 square foot deck at Calgary rates. Our deck cost breakdown runs the same math across other common sizes.

What are the disadvantages of composite decking?

Higher upfront cost, heat retention on south-facing decks in direct summer sun, and a surface that cannot be sanded or refinished once it fades. Board replacement is the only fix for damage, rather than a repair.

What’s better than composite decking?

Nothing outright beats it on lifespan-to-maintenance ratio, though vinyl decking edges it out slightly on moisture resistance at a similar price point, and cedar wins on look and repairability for homeowners willing to keep up the staining schedule.

How often should a composite deck be cleaned?

Twice a year covers most Calgary decks. Once in spring after snowmelt clears ice-melt residue, once in fall before the first snow. Heavily shaded decks under mature trees sometimes need a third pass mid-summer.

A deck that hits its full lifespan almost never gets there by accident. It gets there because the footings were poured right the first time, the staining or cleaning schedule actually happened, and someone dealt with the first soft board instead of the fifth. If a Calgary deck is closer to a rebuild than a repair, our decks page covers a free estimate on what a replacement actually costs for the size and material in mind.