Choosing and Preparing a Base

A good base is the most important thing you can do for a new garden building. A firm, level base keeps the building square, so doors and windows open properly and the roof doesn't twist. It also lifts the timber away from damp ground, which helps your building last for years.

Here's how to choose the right base, get the size right and prepare it properly.

The main types of base

Concrete base

A concrete slab is the strongest and longest-lasting option. It's usually the most expensive, too.

Best for: larger sheds and workshops, log cabins, garden rooms and home offices, and concrete garages, which need a concrete base.
Good to know: concrete needs to be laid level and left to cure fully before a building goes on it. For bigger buildings, it's well worth having it laid professionally.

Paving slab base

Paving slabs laid on a compacted, level sub-base make a solid, practical base for most small and medium buildings.

Best for: most garden sheds, summerhouses and greenhouses.
Good to know: the slabs must be laid flat and level with each other. Uneven slabs will pass their bumps straight on to your building.

Timber frame base

A pressure-treated timber frame raises the building off the ground and lets air circulate underneath. It's quicker to put together yourself than concrete or slabs, and can be levelled on ground that isn't perfectly flat.

Best for: timber sheds and summerhouses, especially on gently uneven ground.
In our store: the Power Sheds Shed Base Kit, the Shedlands Timber Shed Base and the Suresheds Tanalised Airflow Base, each designed to suit that brand's buildings.

Plastic grid and plastic support bases

Plastic grid bases are interlocking panels that are usually filled with gravel. They're lightweight, let rainwater drain through and are easy to lay yourself. Plastic supports that sit under the floor bearers do a similar job, keeping timber clear of the ground.

Best for: smaller and lighter buildings on firm, level ground.
In our store: The Shed Boot plastic shed base kit, which lifts your shed's floor bearers clear of the ground to keep them dry and ventilated.

Bases for specific buildings

Greenhouses: most Elite greenhouses have an integral aluminium base, and Elite base materials are available to anchor and level them on soil, grass, paving or brickwork. Check the product page for your model.
Lifelong steel sheds and garages: Lifelong's installers don't need slabs or concrete. As long as the ground is fairly level, they pack out the footings as part of the installation.
Concrete garages and stores: a concrete base is required.
Garden rooms: TGB Vista Collection garden rooms are subject to a site survey to confirm your base before installation.

How big should the base be?

Aim for a base that is the same size as the building's floor, or very slightly smaller. Don't make it bigger.

It might seem sensible to add a border, but a base that sticks out beyond the walls creates a ledge. Rainwater collects there and splashes back onto the bottom of the cladding, which encourages rot. If you'd like a path or hard standing around your building, leave a small gap or use gravel, which absorbs splashes instead of bouncing them back.

Measure the floor or footprint given on the product page, not the roof. Roofs usually overhang the walls.
Always check the manufacturer's instructions for your building, as some give an exact base size.
Leave working space around the base so you (or your installer) can assemble the building and treat or maintain it in the future. Lifelong, for example, asks for at least 2ft of working area around their buildings.

Getting it level

Use a long spirit level and check in every direction: along the length, across the width and corner to corner.
Check the base is square by measuring both diagonals. They should be the same.
Small errors matter. A base that's out of level can pull a building out of square, so doors stick and the roof can twist.

Drainage and position

Watch where the water goes. After heavy rain, look at where water collects or runs in your garden. Avoid putting your building in a low spot or in the path of run-off.
Don't build straight onto grass or soil. Ground holds moisture, which can creep into the floor and cause damp inside.
Allow airflow. Raised timber bases and floor bearers let air move underneath, which helps keep the floor dry.
Think about access. Leave space to get round the building, and think about how you'll get parts to the spot on delivery day.
Check planning rules. A raised base adds to the overall height of your building. See our planning permission guide.

When to call in Midland Base Works

We work with Midland Base Works, who lay concrete bases that are precision laid, level and load-bearing, with a fast turnaround. We'd recommend a professionally laid base if: