Metal vs Wooden vs Plastic Garden Sheds: Which Should You Buy? (UK Guide)

A galvanised metal shed is the better choice for most UK gardens if low upkeep matters most: it won't rot, resists rust for 15 to 25 years, and needs no repainting. A wooden shed suits you better if looks and insulation matter more than maintenance, since timber handles temperature swings better and takes shelving, windows or a workbench more easily, provided you treat it every 2 to 3 years. A plastic shed sits closer to metal on maintenance, it won't rust or rot and never needs painting, but at Opal it's currently the most expensive of the three per size, so it only wins if zero upkeep matters more than price. Below is the real difference in cost, lifespan, upkeep, security and planning rules for all three, using current UK stock and prices. Prefer to skip straight to our most popular all-round pick, the 7x4ft galvanised metal shed →

In this article

• Metal vs wooden vs plastic shed: quick verdict
• Which is cheaper to buy?
• Which lasts longer?
• Do you need a base?
• Which needs less maintenance, rust or rot?
• Does insulation matter for what you're storing?
• Which is more secure?
• Where does a plastic shed fit in?
• Do you need planning permission?
• Which shed suits your garden?
• FAQ

Metal vs wooden vs plastic shed: quick verdict

Here's the comparison in one table. Prices below are for in-stock Opal Retail sheds, so they're real figures, not averages. We've kept two size/price tiers for metal and wood, budget and larger, plus one plastic option, since this is a three-way comparison rather than a straight two-way one.

Which is cheaper to buy, metal, wood or plastic?

At the small end, wood and metal sit close together, both from under £100. The gap opens at larger sizes: among the sheds featured in this guide, wood tops out at £169.99 for a compact double-door model, while galvanised metal scales up to 13x11ft for £436.99, since steel panel construction handles a bigger footprint more cheaply than an equivalent timber frame and roof. Plastic is the outlier, and the most expensive per size at Opal (see the plastic section below), so don't assume it's the budget option, you're paying for zero maintenance, not a lower price.

So for a small shed, price isn't the only deciding factor, weigh it against looks and maintenance appetite. Above roughly 7x5ft, metal is usually the cheaper route to the space you need, with plastic the priciest. Leave a wooden shed untreated and you'll likely pay for repairs or an early replacement, which erases any saving, budget £15 to £25 a year for wood preserver.

Budget wooden pick

Wooden Garden Shed with Shelves and Bolt Latch, 75x56x115cm

Solid fir wood with built-in shelving, a compact option for a tight corner where looks matter as much as storage.

From £98.99 View shed →

Which lasts longer, a metal shed or a wooden shed?

A galvanised steel shed is built from zinc-coated panels, which is what stops rust taking hold. A well-built galvanised shed typically lasts 15 to 25 years with essentially no maintenance, and can outlast a wooden equivalent in exposed or coastal gardens. The same zinc coating process is used across UK construction for this reason, the Galvanizers Association explains how it works if you want the detail.

Wood is more variable. A cheap dip-treated shed is only rated for about 10 years, since the treatment sits on the surface rather than soaking in. A pressure-treated shed, where preservative is forced into the timber, can last up to 25 years, but only if you keep re-treating exposed cuts and bare wood. Done badly, either can fail within two or three years: metal from condensation and rust without enough ventilation, wood from rot when timber sits in standing water or goes untreated. Plastic sits apart: polypropylene panels don't rust or rot, though Opal's listings don't publish a specific lifespan rating, so treat it as a fair trade-off, not a proven longer life.

Mid-range metal pick

7x4ft Metal Garden Shed with Apex Roof and Sliding Doors

Lockable sliding doors and roof vents, the size most gardens settle on for bikes, mower and tools together.

From £164.99 View shed →

Do you need a base for a garden shed?

Yes, for all three materials. A shed placed straight onto grass or bare soil traps moisture underneath, the single most common reason any type fails early. You need a firm, level, well-drained surface: paving slabs, a concrete pad, or interlocking plastic grids over compacted gravel all work. Gravel alone isn't solid enough and can shift in bad weather, so it needs a grid or edging to hold it in place.

Some metal sheds come with a foundation kit included, removing this step. Plastic sheds vary by model: Opal's smaller 5x3ft plastic shed has a floor panel built in, while the larger 4x6ft and 8x6ft plastic sheds ship with a galvanised foundation kit rather than a floor panel, so you still need a level base underneath, always check the individual listing rather than assuming. Fitting a shed without a floor panel, raise it off bare soil regardless of material, it's what stops the base rotting, rusting or sitting in condensation.

Recommended add-on

Shed Base ECO Plastic Grids

Interlocking grids that give any shed, metal, wood or plastic, a level, well-drained base without pouring concrete.

From £69.99 View base kit →

Which needs less maintenance, rust or rot?

This decides most purchases. Metal sheds don't rot, paint or warp, but can suffer condensation, since metal doesn't absorb moisture like wood, and rust, usually starting at scratches or joints where the coating is compromised. Both are manageable: a base that lifts the floor off wet ground plus a vent left open cuts condensation right down, and touching up any scratch with a galvanised repair spray stops rust before it starts.

Wooden sheds have the opposite problem: left untreated, damp gets into the joints and base first, and rot spreads once it sets in. The fix is simple but has to happen: re-treat with a quality preservative every 2 to 3 years, more often on the weather-facing side, and replace roof felt before it visibly fails. Plastic sheds are the lowest-maintenance of the three on paper, polypropylene panels don't rust, rot or need painting, a wipe with a damp cloth is the full job.

Does shed insulation matter for what you're storing?

Wood insulates better than metal or plastic, since timber doesn't conduct heat and cold the way steel or polypropylene panels do. A metal or plastic shed runs noticeably hotter in summer sun and colder on a frosty morning than a wooden one the same size.

Whether that matters depends on what's going in it. For a mower, bikes, tools and garden furniture, it's irrelevant. It matters more if you're storing paint or temperature-sensitive chemicals, or want to work inside the shed, in which case wood, or metal/plastic with insulation board added, is the better start.

Which is more secure, a metal, wooden or plastic shed?

A metal shed is harder to force open with a crowbar, which is why it's the common choice for bikes, tools and anything insurers ask about. The trade-off is panel thickness: cheap metal sheds with thin panels can be dented or bent out of shape, so check the gauge before buying rather than assuming all metal sheds are equal. A wooden shed with a solid frame and a good hasp and staple lock can be just as secure, security comes down more to the lock and hinges than the wall material. Plastic sheds take a standard padlock too, but the panels are lighter and less rigid than steel or timber, so they're a step down for anyone storing high-value kit.

Either way, fit your own padlock rather than relying on the standard lock, and check whether your home insurance requires a specific lock rating for outbuildings if you're storing anything of real value.

Compact wooden pick

Wooden Garden Shed with Double Doors and Storage Table, 139x75x160cm

Double doors and a lift-out storage table make this a tidy fit for a patio or smaller garden where a full-size shed won't go.

From £169.99 View shed →

Where does a plastic shed fit in?

Plastic sheds are the newest of the three options in Opal's range, and the positioning is different from what most people expect. They're not the budget choice, they're the low-maintenance choice, and you pay a premium for it: Opal's plastic sheds currently run from £218.99 for a small 5x3ft unit to £485.99 for an 8x6ft, both above a similarly sized metal or wooden shed.

What you get for that: polypropylene panels that won't rust, rot, fade or need painting, ever, an aluminium or galvanised steel frame for rigidity, and (on the larger models) a galvanised foundation kit included in the box. The trade-off is weight and rigidity: plastic panels flex more than a steel or timber wall, so they're a better fit for tools, bikes and general storage than for anything you'd want to lean on or that needs a fully rigid structure.

A plastic shed makes sense if: you want the lowest possible ongoing maintenance of the three materials, you don't mind paying more upfront for it, and you're storing general garden kit rather than heavy or high-value items.

Plastic pick

4x6ft Plastic Garden Shed with Window and Foundation Kit

A mid-size plastic shed with a side window and galvanised foundation kit included. No floor panel, so stand it on a level base such as paving or concrete.

From £316.99 View shed →

Do you need planning permission for a garden shed?

Most UK gardens can fit a shed under permitted development rules without planning permission, provided it doesn't cover more than half the garden, sits behind the front of the house, and stays under the height limits (2.5m within 2m of a boundary, up to 4m further away). These rules apply equally regardless of material, only size, height and position matter. See our complete guide to garden shed planning permission for the full breakdown, or check the Planning Portal.

Which shed suits your garden?

Choose metal if: you want to buy once and not think about it again, you need a larger footprint without a large price jump, your garden is exposed to wind or coastal weather, or the shed is purely for tools, bikes and equipment rather than anything temperature-sensitive.

Choose wood if: the shed sits somewhere visible and you want it to look good, you're happy to re-treat it every couple of years, you want to add windows, shelving or a workbench easily, or you plan to spend time working inside it rather than just storing things.

Choose plastic if: zero ongoing maintenance is the priority above everything else, you're storing general garden kit rather than heavy or high-value items, and you're comfortable paying more upfront than a similarly sized metal or wooden shed for the lower-upkeep trade-off.

Premium metal pick

13x11ft Metal Garden Shed with Apex Roof and Sliding Doors

Serious storage for bikes, mower and furniture together, at a price a comparable timber building would struggle to match.

From £436.99 View shed →

Frequently asked questions

Will a metal shed rust?

Galvanised steel resists rust well thanks to its zinc coating, but rust can start wherever that coating is scratched, usually at joints or during assembly. Touching up any scratch with a galvanised repair spray as soon as you spot it stops it spreading.

Do wooden sheds need treating every year?

Most manufacturers recommend re-treating every 2 to 3 years for pressure-treated timber, or annually for cheaper dip-treated sheds where the factory coating fades faster. Skip it for a couple of years running and the timber greys and the joints start to soften.

Do metal sheds get condensation?

Yes, more than wood. Metal doesn't absorb moisture, so temperature changes cause water to form on the inside surfaces and drip onto whatever's stored beneath. A base that keeps the floor off wet ground, plus a vent left open, cuts condensation down significantly. Sheds with eave vents and an anti-drip roof coating handle this far better than budget models without either.

Do plastic garden sheds need any maintenance?

Very little. Polypropylene panels don't rust, rot, fade or need painting, Opal's plastic sheds are cared for with a wipe-down using a damp cloth. Check that any padlock and hinges stay free-moving, and make sure the shed is anchored or weighted, since plastic panels are lighter than metal or timber and a lightweight shed can shift in strong wind if not properly secured to its base.

What size shed do I need for a mower and tools?

A 6x4ft shed is usually the minimum for a mower plus hand tools, but if you also want shelving or a workbench, go up to 7x5ft or larger. Measure your mower's full length including the handle before choosing, it's the dimension people most often forget.

Can I put a shed on grass or decking?

Not directly. Grass traps moisture against the shed floor and will rot a wooden base, rust a metal one, or leave a plastic one sitting unevenly, within a year or two. Decking can work if it's solid, level and has gaps for drainage, but a proper base underneath is still the safer option.