Large Garden Sheds UK: A Buying Guide for Serious Storage

If you need to fit a mower, a couple of bikes, a full tool kit and still have room to move, look at anything from 9x6ft upward. A 9x4ft shed suits mower-plus-tools storage on its own. If you want a proper workshop bench as well, or you're storing garden furniture over winter, size up again to 11x9ft or the 13x11ft range. The short version: work out what has to fit first, then add a bit of headroom, because nearly every shed owner who buys "just big enough" ends up wishing they had bought one size up.

In this article

• What size large garden shed do I actually need?
• What do the common large shed sizes actually look like?
• Do you need planning permission for a large shed?
• What base does a large shed need?
• How do you stop condensation and rust in a large metal shed?
• How is a large shed delivered, and can one person put it up?
• FAQ

What Size Large Garden Shed Do I Actually Need?

Work backwards from what actually needs to live in the shed, not from a size you have seen advertised. A few honest anchor points:

• A ride-on mower on its own needs roughly 9m² of floor space to get in and out without a three-point turn.
• Two or three adult bikes need about 6m², more if you want to wheel them past each other rather than lift them over.
• A proper workbench, with room to actually stand and use it, wants at least 8m².
• Garden furniture stored flat over winter (a table, four to six chairs, a parasol) eats space fast, more than most people expect.

Add those needs together and round up. If two uses on that list apply to you, you are already looking at 9x6ft or bigger. If three or more apply, or you want a genuine workshop corner as well as storage, go straight to 11x9ft or 13x11ft. Our own small garden sheds guide covers the other end of the range, for anyone whose list is shorter than this.

What Do the Common Large Shed Sizes Actually Look Like?

UK sheds are still sold in feet, which makes size hard to picture. Here is what our large range actually covers, using each shed's real internal floor area (not a rough conversion from the nominal feet size) so you can compare against your own garden.

One thing worth knowing before you order: sheds are usually named after their nominal frame size, and the real internal floor area, which is what actually matters for fitting things in, is smaller than that headline figure suggests. If your garden or your base is a tight fit, check the internal dimensions in the product specification rather than just the headline size.

Entry-level large

9x4ft Metal Garden Shed, Pent Roof

Galvanised steel, sliding doors, room for a mower and full tool kit. The smallest size we would call genuinely "large".

From £191.99 Shop this shed →

Most popular large size

9x6ft Metal Garden Shed, Apex Roof

Double sliding doors and 4.83m² of real internal floor space. Mower, bikes and tools with room to actually walk round them.

From £245.99 Shop this shed →

Do You Need Planning Permission for a Large Shed?

Most garden sheds fall under permitted development and do not need planning permission, provided they stay under 2.5m tall within 2m of a boundary (or up to 4m with a dual-pitch roof further away), and outbuildings together do not cover more than half your garden. We cover the full rules, including boundary distances and height limits, in our garden shed planning permission guide, so we will not repeat it all here.

What is worth flagging specifically for large sheds: the 50% garden coverage limit is the one buyers in this size bracket actually bump into. A small shed almost never gets close to it. A 13x11ft shed (around 13.3m²) plus an existing extension, patio structure or greenhouse can add up faster than people expect, particularly on a smaller plot. Measure your total outbuilding footprint against your garden area before you order, not after.

What Base Does a Large Shed Need?

A base matters more as sheds get bigger, because there is more weight and more wind-loaded surface area for it to support. For anything 9x6ft and up, a solid, level base is not optional.

• Concrete slab is the most solid option and the one most large-shed manufacturers recommend, particularly if you are storing anything heavy like a ride-on mower.
• Paving slabs on a compacted, levelled sub-base work well for most large metal sheds and are more DIY-friendly than a poured slab.
• Plastic grid bases are a faster, lower-cost option for level ground that drains well, and they avoid a full concrete job.

Whichever base you choose, get it dead level before the shed arrives. A large metal shed will show every dip in an uneven base as a door that will not close properly or a roof seam under strain.

Base accessory

Eco Plastic Grid Shed Base

A level, well-draining base you can lay in an afternoon, available in sizes right up to 13x11ft to match our largest sheds. Good middle ground between gravel and a full concrete pour.

From £69.99 Shop shed bases →

How Do You Stop Condensation and Rust in a Large Metal Shed?

Metal sheds condense, even on a good concrete base with a damp-proof membrane underneath. It is a genuine trade-off of the material, not a fault, and it is worth planning for rather than being surprised by it. Warm, moist air inside the shed meets cold metal, especially the roof, and drips form, particularly on frosty mornings.

The fixes people actually use and report working:

• An anti-condensation roof lining or fleece, fitted to the underside of the roof panels.
• Ventilation grilles high on the walls, so moist air has somewhere to go instead of pooling under the roof.
• Keeping anything metal (tools, bike frames) off the bare floor, on a shelf or a rubber mat, since condensation collects on cold metal surfaces first.

None of this is unique to any one brand of metal shed; it is simply how the material behaves. If condensation is a dealbreaker for you, particularly for storing power tools long-term, a wooden shed manages moisture differently and is worth considering for smaller storage needs, even though our large-size range is metal.

How Is a Large Shed Delivered, and Can One Person Put It Up?

Large sheds arrive flat-packed, usually on a pallet, and delivery is typically kerbside; the panels are heavy and you will need to move them into the garden yourself. Budget for that when you are planning delivery day, especially if there are steps, a narrow side gate, or any distance between the road and where the shed is going.

For assembly: the manufacturer's own guidance recommends three people for every size in our large range, from the 9x4ft right up to the 13x11ft, not just the biggest ones. Panels are large and heavy enough that two people alone will struggle to hold a wall steady while fixing it, let alone lift a roof section into place. Set aside a full day, not an afternoon, for anything in the 9x6ft to 13x11ft range, and check the weather forecast; wind makes handling large panels considerably harder.

Top of the range

13x11ft Metal Garden Shed, Apex Roof

12.28m² of real internal floor space. Room for a ride-on mower, a full workshop bench and garden furniture storage together.

From £436.99 Shop this shed →

Frequently asked questions

What size large garden shed do I need?

Work out what has to fit (mower, bikes, tools, a workbench, furniture) and add each requirement's floor space together, then round up. A mower alone needs around 9m², bikes need 6m² or more, and a usable workbench needs at least 8m². Combine two or more of those and you are into 9x6ft or bigger territory.

Do I need planning permission for a large garden shed?

Usually not, provided it stays under the permitted development height and boundary rules. Large sheds are more likely to bump into the 50% garden coverage limit than small ones, so check your total outbuilding footprint against your garden size before ordering. Full detail is in our planning permission guide.

Why is my shed smaller than the size it's advertised as?

Sheds are usually named by their nominal frame size, and the true external footprint, particularly the base measurement, can come in a little under that. Always check the base/plinth dimensions in the product specification if your space or base is a tight fit, rather than relying on the headline size alone.

Do large metal sheds get condensation, and how do I stop it?

Yes, and it happens even with a good base and damp-proof membrane; it is a normal property of metal, not a fault. An anti-condensation roof lining, high-level ventilation grilles, and keeping metal items off the bare floor are the fixes that genuinely help.

What base does a large shed need?

A level, solid base: concrete slab, paving slabs on compacted hardcore, or a plastic grid base for well-draining ground. Get it perfectly level before the shed arrives, since an uneven base shows up as sticking doors and strained roof seams later.

Can one person assemble a large shed?

No. The manufacturer's own guidance recommends three people for every size in our large range, including the smallest 9x4ft, not just the biggest ones. Set aside a full day and check the wind forecast before you start.