What Is a Concrete Slab and When Do You Need One?

What will the slab be used for?

Sheds and garden buildings

Check the supplier’s base requirements before arranging the work. The building’s footprint, door position, finished height and any services should be agreed early. A level base is important, but so is dealing with water around its edges.

Garages and vehicle use

A slab carrying vehicles needs to be designed for that use. Vehicle loads, thresholds, finish, drainage and any equipment or fixings should be considered before a price is agreed. Do not copy the detail for a lightweight garden shed.

Extensions and new-build floors

A building floor needs to fit the construction design, including relevant moisture protection, insulation, services and finished floor levels. A ground-bearing slab and a suspended floor are different arrangements; the drawings should establish which is appropriate.

Structural rafts and specialist loads

A structural raft is part of the foundation design, not simply an oversized garden base. Machinery, heavy storage, hot tubs or other concentrated loads also need to be declared so that the appropriate design advice can be obtained.

Why the layers below the concrete matter

Concrete is only one part of the construction. The prepared ground, supporting layers and any specified membranes, insulation or reinforcement must suit the use and the site. The government’s Approved Document A covers structural elements including floors and foundations in England.

There is no single safe slab thickness, concrete grade or reinforcement detail for all of these uses. Those details should come from the relevant design or supplier requirements and the site assessment, not a generic calculator result.

Our concrete slabs and bases service in Surrey explains the work we can discuss, from preparation and access to the pour and finish.

What affects the cost of a concrete base?

• The area, shape and specified construction.
• Removing an existing base, paving, vegetation or other material.
• Ground conditions and the preparation needed.
• How concrete and other materials can reach the location.
• Spoil removal, loading space and disposal arrangements.
• Edges, levels, drainage and the required finish.
• Any design, inspection or specialist requirements.

A price per square metre without these details can hide substantial differences in scope. Ask for the inclusions, exclusions and assumptions in writing. For restricted sites, our site access checker can help you organise the information to send; it does not confirm whether plant or delivery equipment will fit.

What to send when asking for a quote

1. Your postcode and the intended use of the base.
2. Approximate length and width, plus drawings or the building supplier’s requirements if available.
3. Photographs of the proposed position, the route in and the delivery area.
4. The preferred finished level in relation to doors, paths or adjoining buildings.
5. Any known drains, cables, pipes, trees or previous ground problems.
6. Whether you need removal of an old base, excavation, drainage and making good included.

If you are also planning an extension or new build, share the current structural and drainage information. That helps avoid separately pricing work that needs to be coordinated.

Concrete bases in Guildford, Woking and Surrey

A Jones Contractors is Guildford-based and works across Surrey. We can discuss smaller concrete base jobs as well as slabs forming part of groundworks and foundations or a larger building project.

See our coverage for Guildford and Woking, then send your dimensions and photos or call 07414 577346. We can establish what further information is needed before agreeing a firm scope.

Frequently asked questions

How thick should a concrete slab be?

It depends on the intended use, loads, supporting ground and design. A shed supplier’s recommendation should not be reused for a garage, extension floor or structural foundation.

Can you build a base where access is narrow?

Access needs checking. Send photographs and the narrowest measurements, including any steps or turns. Material handling and waste removal can affect the method and cost.

When can I put a building or vehicle on a new slab?

Follow the project-specific advice for curing, loading and any finishes. The surface looking dry does not prove that it is ready for the proposed load.

Can I use a volume calculator to order the concrete?

A calculator can help estimate a quantity from dimensions. It cannot choose the slab design or check the ground. Confirm the dimensions, specification and ordering allowance with the responsible contractor before placing an order.