Cedar or aluminum is the great aesthetic-versus-practical fork in greenhouse framing — the warm, traditional timber structure that belongs in a kitchen garden against the rot-proof, maintenance-free extrusion that dominates the modern kit market. Both build excellent greenhouses. They age, cost, and demand differently, and this comparison lays out exactly how.
The Materials, Honestly Stated
Western red cedar (and similar naturally durable timbers) resists rot and insects through its own oils, holds screws and glazing bars with woodworker-friendly forgiveness, and carries the thermal and visual warmth no metal matches. Wood is also a mild insulator — cedar frame members don't conduct heat out of the structure the way metal does — and a well-built cedar frame is heavy and stiff, which wind respects. Its demands: periodic care (a re-oil or leave it to silver honestly), more expensive and heavier sections, and joinery that rewards skill.
Extruded aluminum neither rots, rusts, warps nor feeds insects; it holds glazing in precise factory channels, ships flat-packed at hobby prices, and asks for nothing but an annual bolt check for decades. Its vices are character-shaped: thin economy extrusions flex and rack in wind (the panel-popping failure chain from our survivability pillar), bare metal frames conduct heat outward as thermal bridges, and no one has ever photographed one for a garden-design magazine.
| Factor | Cedar frame | Aluminum frame |
|---|---|---|
| Longevity | Decades with basic care; silvers or re-oils | Effectively indefinite; zero care |
| Maintenance | Optional oiling; inspect joints | Annual bolt re-torque |
| Thermal behavior | Mild insulator; no cold bridging | Conducts heat; frame is a thermal bridge |
| Strength feel | Heavy, stiff sections; wind-calm | Depends on extrusion depth; economy kits flex |
| Weight & shipping | Heavy; often local/custom or premium kits | Light flat-pack; ships anywhere cheap |
| Glazing fit | Wood rebates; suits glass beautifully | Precise channels; suits polycarbonate systems |
| Cost | $$$ tier for equivalent size | $–$$ tier entry, $$$ premium lines |
| Looks | The garden-magazine structure | Utilitarian to tidy-modern |
Durability in the Real World
Both materials outlive their owners' enthusiasm when treated right. Cedar's risk points are ground contact and standing moisture — a cedar frame on a proper base with functioning gutters lasts generations, while one with soil piled against the sill plate invites the only rot cedar can't refuse. Aluminum's risk point is under-specification: the metal is immortal but a bargain kit's thin sections rack in wind and pop panels, so aluminum longevity is really a buying decision (deeper profiles, bracing, the anchoring from our anchoring guide) rather than a maintenance one. Coastal salt air mildly favors cedar or marine-grade anodized aluminum; either beats steel there.
The Assembly and Repair Experience
Ownership differs day to day, too. Aluminum kits arrive as hundreds of catalogued extrusions and fasteners — assembly is patient inventory work, and repairs mean ordering the exact part number. Cedar builds (or kits) are carpentry: fewer, heavier members, joined with skills and screws any woodworker owns, and repairable forever with a saw and a lumberyard — there is no discontinued part number for a 2x4. Glazing swaps favor cedar's forgiving rebates for glass and aluminum's precise channels for polycarbonate systems; both are afternoon jobs once, and lifetime skills after.
Cost Over Ten Years
Aluminum wins the sticker comparison decisively — entry kits cost less than the lumber alone for an equivalent cedar structure. Cedar closes some of the gap over time: nothing to replace, glazing bars that accept new glass or panels indefinitely, and resale/property value that a premium timber greenhouse genuinely carries. But honestly costed, aluminum remains the value play and cedar remains the heirloom play; buyers choosing cedar are buying the decade view and the daily view out the kitchen window, not a spreadsheet win.
Which Grower Is Which
Choose cedar if the greenhouse is landscape as much as equipment, if you're glazing with glass, if you enjoy (or commission) real joinery, and if the budget reaches. Choose aluminum if the mission is growing per dollar, if you want a proven kit up this month, if maintenance appetite is zero, or if the structure may someday move house with you. And in cold climates, note the quiet thermal point: a cedar frame's non-conductive members and a modern aluminum kit's thermally broken premium extrusions both address the cold-bridging that budget metal ignores — one more reason the glazing choice still matters more than the frame material for winter heat bills.
Compare both frame worlds
Cedar greenhouse kits and premium aluminum lines cross-shop directly at the quality end of the market — compare equivalent footprints with glazing included, and weight the decade of ownership, not just the checkout total.
Our Verdict
Aluminum is the rational default: cheaper, lighter, zero-maintenance, and available in honest engineered tiers — the working answer for most growers, as our aluminum roundup details. Cedar is the right upgrade when the greenhouse is also architecture: stiffer in the wind, warmer in every sense, and the only frame that improves the view. Buy aluminum for the growing; buy cedar for the garden.
Frequently Asked Questions
How long does a cedar greenhouse last?
Generations, with basics observed: keep soil off the sill, keep gutters working, and either re-oil the timber periodically or let it silver naturally. Cedar's oils resist rot and insects without treatment.
Do aluminum greenhouse frames need maintenance?
Almost none — an annual bolt re-torque and glazing-channel inspection. Aluminum neither rots nor rusts; its real longevity risk is under-specified thin extrusions flexing in wind, which is a buying decision rather than a maintenance one.
Is a wood or aluminum greenhouse warmer?
Wood frames don't conduct heat outward, so cedar avoids the cold bridging of bare metal members. In practice glazing choice dominates winter heat retention — twin-wall or thicker polycarbonate matters more than the frame material.
Why are cedar greenhouses so expensive?
Quality timber costs more than extruded aluminum, sections are heavier to ship, and construction involves real joinery. Buyers are paying for stiffness, looks, and heirloom longevity rather than minimum cost per square foot.