What Size Shed or Greenhouse Do I Need?

"Which size?" is a question we're often asked. Buy too small and you'll be tripping over the lawnmower within a year. Buy too big and you lose garden you'd rather keep. This guide walks you through choosing the right size of shed, summerhouse or greenhouse for your garden and how you'll use it.

Nominal size vs actual size

Garden buildings are usually sold by a rounded size in feet, such as 8×6 or 10×8. This is the nominal size. The real, measured size can be a little different, and the difference varies between manufacturers and models.

• Some manufacturers quote the size of the base or floor, others the outside of the walls.
• Roofs normally overhang the walls, so the building takes up more space at roof height than on the ground.
• Greenhouse sizes can differ quite a lot from the name. For example, an Elite greenhouse sold as "12×6" can measure 10'5" wide. Our Elite buying guide explains this.
• Timber thickness can be nominal too. Timber is often named by its sawn size before planing. On the Sovereign range, for example, "16×125" standard shiplap finishes at around 12mm thick, and we show the finished figure on our product pages.

The rule is simple: plan your space around the actual external dimensions and overall height on the product page, not the name. If a product page doesn't show what you need, ask us before you order.

Step 1: Measure what's going in

Make a list of everything you want to keep in the building and measure the biggest items. Common ones are:

• a lawnmower (and whether you want to wheel it straight in)
• bikes, which need length as well as a wide door
• garden furniture and cushions over winter
• a workbench, which needs standing room in front of it
• shelving, which takes around 30–45cm of depth along a wall

Then add space to move. You need to be able to reach the back without unloading everything. Sheds tend to fill up faster than expected, which is why we often suggest going one size bigger.

Typical shed sizes and what fits

These are general guides. Floor areas are worked out from the nominal size, so real areas will vary slightly.

Ranges vary in how far they go. The Power Apex Shed, for example, runs from 4×4ft to 20×8ft, and the Suresheds Pent-Dale from 4×4ft to 14×10ft. Browse all garden sheds to compare.

Typical greenhouse sizes

Greenhouses fill up fast, so if in doubt go one size bigger. A wider greenhouse gives you a proper path down the middle as well as staging or a border on each side. Compare the greenhouse range, or read our Vitavia and Elite buying guides.

Step 2: Measure your garden, not just the gap

Mark out the footprint on the ground with string or garden canes and live with it for a day or two. Then check:

• Working space all round. You need room to build the building and to treat or paint it every year or two. Allow at least 60cm on every side you'll need to reach. Some manufacturers ask for more.
• Door swing and access. Can you get the mower or bikes in without a three-point turn? Is there a clear path to the door?
• Roof overhang. Measure the space at roof height as well as floor level, especially near fences and trees.
• Light. Greenhouses need as much light as possible, ideally away from the shade of trees and buildings. Sheds and summerhouses are more flexible.
• Delivery route. Big panels and log bundles need a clear route from the road to the site. Measure side gates and paths.

Step 3: Check height and size limits

Size and position affect whether you need permission. In England, under the permitted development rules for outbuildings on the Planning Portal:

• A building within 2 metres of a boundary must be no more than 2.5m high overall.
• Further from the boundary, the limit is 4m for a dual-pitched (apex) roof or 3m for other roofs, with eaves no higher than 2.5m.
• Outbuildings and extensions together must not cover more than half of the land around the original house.

Floor area matters for building regulations. A detached building under 15m² with no sleeping accommodation does not normally need approval. Between 15m² and 30m², it normally doesn't either, as long as there's no sleeping accommodation and it is at least 1 metre from any boundary or built substantially of non-combustible materials (Planning Portal).

For reference, a 16×10ft building is about 14.9m² and a 16×12ft building about 17.8m², so larger workshops and garden rooms can cross the 15m² line. Our planning permission guide covers the rules in full, including Scotland and Wales.

Pent or apex: does the roof change the size?

A pent roof slopes one way and is usually lower overall, so it's often the easier choice close to a fence or under the 2.5m limit. An apex roof gives more headroom down the middle, which is handy for a workshop or for storing tall items. If height is tight, compare the overall height of each style in the size you want.

Common questions

What is the most popular shed size?

Around 8×6ft is the most common all-round size for a typical family garden. It holds a mower, tools, a couple of bikes and shelving. If you have the space, 10×8ft gives you room to grow into.

What does nominal size mean?

Nominal size is the rounded name a building is sold under, such as 8×6. The actual measured size can be slightly different depending on the manufacturer, so always plan around the real dimensions on the product page.

How much space should I leave around a shed?

Leave enough room to assemble the building and to reach every wall for treatment and maintenance. Around 60cm on each side you need to reach is a sensible minimum, though some manufacturers ask for more.

What size greenhouse should I buy?

An 8×6ft greenhouse suits most keen gardeners, with staging on one side and a border on the other. A 6×4ft is a good first greenhouse. If you are unsure, go one size bigger, as greenhouses tend to fill up quickly.

This guide is general information, not legal or professional advice. Always check planning and building regulations with your local council before you buy.