A kit garden shed arrives on a pallet and goes up in a weekend. A shed built to measure costs several times as much and involves proper site work. So the real question is not which one is better: it is what you expect from the building, and for how long.
What you are buying when you buy a kit
The kit market is easy to read, and it deserves credit for its consistency. Three ranges stand out by the thickness of the boards: around 19 mm for lightweight sheds, 28 mm for the mid-range, and 44 mm or more for models sold as habitable. The species is almost always spruce or fir, supplied untreated or pressure-treated. The walls are made of interlocking boards stacked on top of each other, with no frame. The roof is a thin panel covered with bitumen felt.
For storing tools, a bike or garden furniture over the winter, it is a sensible purchase — and we say so without reservation. Set on a sound base, with a well-maintained roof, a kit does the job it is asked to do.
That said, you still have to do the three things the instructions do not explain: prepare a level, free-draining base rather than setting it on bare earth, lift the floor off the ground so that air can circulate underneath, and treat every cut made during assembly with an end-grain preservative. Those three steps take half a day and make all the difference. Most of the sheds we see ageing badly were not badly made: they were badly installed.
What a kit cannot do, however, is adapt. It is designed for mass production, not for your plot, your exposure or your use. Three limitations follow from that, and they are always the same.
First limitation: the timber is not chosen for its exposure
The standard that governs this does not classify timber, it classifies situations. Timber under a ventilated cover is in use class 2. Cladding exposed to rain but drying quickly between showers is in class 3.1. The same cladding, poorly ventilated and slow to dry, moves into 3.2. And anything in contact with the ground is in class 4.
Against that, each species has its own natural durability, rated from 1, very durable, to 5, not durable. Spruce and fir — the two species used in kits — are rated as having low durability. Douglas fir and larch do better, sweet chestnut and oak better still.
The principle fits in one sentence: the durability of the species must cover the use class of the situation. A shed in untreated spruce standing outdoors is timber meant for indoor use placed in an outdoor situation. Pressure treatment corrects this — provided it is genuine, and every cut made during assembly is treated with end-grain preservative. On a kit trimmed with a jigsaw on a Sunday afternoon, nobody does it.
Second limitation: the connection to the ground
This is where sheds fail, and always from the bottom up. A floor laid straight onto a slab holds a film of water every time it rains. Splashback soaks the bottom twenty centimetres of the walls. Without an air gap under the floor, nothing dries.
What we do instead is nothing spectacular: metal post bases that lift the timber a few centimetres off the ground, ventilated point supports rather than a continuous base, and airflow under the floor. Timber lifted off the ground and ventilated moves from class 4 to class 3 — and the lifespan of the structure changes by an order of magnitude for a negligible extra cost.
Third limitation: the roof and the overhang
Bitumen felt can be replaced; that is no disaster. A missing overhang, on the other hand, is a design flaw: with no eaves, water runs down the walls with every shower, and the cladding moves permanently to the wrong side of the standard.
Thirty to fifty centimetres of overhang, a decent pitch and a roof covering built to last cost little at the time of construction. Yet they are what decides the condition of the shed ten years on.
What a built structure changes
A built shed is not a better kit: it is a structure designed before it is cut.
- The species is chosen element by element — class 4 treated timber where ground contact requires it, Douglas fir free of sapwood where it is exposed but ventilated, perfectly suitable spruce under the roof.
- Sections are calculated for the actual span and load: snow, high-level storage, solar panels planned for later.
- Connections are properly jointed, not simply screwed into end grain.
- The shape follows the site — a slope, a boundary wall to lean against, a height capped by planning rules, a tree to keep.
- And the structure becomes something else: a well-lit workshop, an open, ventilated log store, a bike shelter, a plant room, a lean-to that extends the house instead of sitting next to it.
The uses that tip the balance
In practice, it is almost never the floor area that decides, it is the use. Four requests come up regularly, and none of them can be handled properly with a catalogue model.
- The workshop. As soon as it houses a workbench, tools and lighting, it needs headroom, a floor that does not move, a door wide enough to get a machine out, and a route for the electricity supply planned from the design stage.
- The log store. Firewood needs air and shade, not an enclosed space. A log store is a largely open, roofed and ventilated structure — the opposite of a kit shed, which is often turned into a log store and leaves its contents to go mouldy.
- The bike shelter. Open on one side, shallow, leaning against a wall, with a floor that does not hold water and direct access from the gate. A layout no catalogue offers, because it depends entirely on the site.
- The lean-to. The one that extends the house rather than standing in the garden: it has to follow the pitch, the line and often the look of the existing building. This is where the gap between a designed structure and an off-the-shelf model becomes visible from the street.
Three questions to decide
How long do you want it to last? If the horizon is a few years and the use is strictly storage, a kit is an honest choice.
Does the shed sit next to the house, or form part of it? As soon as it leans against the house, is visible from the street, or stands in an area where external appearance is regulated, it becomes part of the architecture — and a catalogue model shows.
Does the site impose anything? A slope, ground that moves, narrow access, rainwater to manage: all constraints a kit ignores by design.
If all three answers are “it doesn’t matter”, buy a kit. We will tell you so just as frankly on the phone as we do here.
Either way, planning permission comes first
Kit or bespoke, the planning rule is the same: above 5 m² of footprint, a prior declaration (déclaration préalable) is normally required, and full planning permission (permis de construire) takes over above 20 m². In a protected area, the exemption for small structures no longer applies. Better to check before ordering than to find out after building.
Let’s talk about your project
A shed is a small structure, but it is a structure: it bears loads, it takes the weather and it ages outdoors. That is precisely why it should be designed before it is built.
Tell us what you want to use it for, where it will stand and what the site imposes. We will tell you frankly whether a kit will do — and if a bespoke build is justified, we will visit and provide a detailed, free, no-obligation quote.
