Yes. A wooden garage needs a level base that can support the building, vehicles and any stored equipment.
Chart garages require a concrete slab with a single course of semi-engineering brickwork between the concrete and timber frame.
The exact specification will depend on the garage design, ground conditions, drainage and expected loads. Chart Garages provides a detailed base plan for your groundwork contractor to follow.
Below, we explain the main stages involved and the details to discuss with your contractor.
This guide covers nine main stages of laying a concrete base for a garage. Your groundwork contractor should complete them carefully and follow the detailed base plan we will supply for your building.
To build a concrete base for your timber garage, you will likely need:
The exact materials and quantities will depend on the base plan, site conditions and garage design. Use the materials and specifications shown on the base plan.
Before preparing the site, check whether the garage needs permission. Read our guide to planning permission for garages, carports and carriage houses.
Here are the nine steps to laying a concrete base for a timber garage.
Before clearing or digging, ask your contractor to check the base plan, ground conditions, levels and drainage.
They will also need to locate underground cables, pipes and drains. Do not start digging until they have identified any buried services. You can find more information in the HSE guidance on safe excavation.
If the garage will sit close to a boundary, read our guide to building a timber garage near a boundary.
First, remove all vegetation and debris, including rocks and roots, from the area. Clear enough space for the slab shown on the base plan and for the contractor to work safely around it.
Mark the base using the dimensions shown on the plan. Use pegs and string lines to mark the corners and edges. Measure the diagonals to check that the base is square, then check all measurements against the base plan before digging.
Dig out the soil to create a level surface. The excavation depth will depend on the ground conditions, garage design and weight the base needs to support. Heavy vehicles may require a different slab specification.
Your contractor should check the ground and prepare it for the base. They may also need to compact it or remove unsuitable soil.
Next, secure timber shuttering around the base to create the formwork for the concrete.
Brace the boards firmly so they do not bow or move when you pour the concrete. Your contractor should choose suitable support spacing for the base design.
Once the formwork is secure, lay the hardcore over the prepared ground and compact it using suitable equipment, such as a powered plate compactor.
A 6-inch layer usually works well for standard-size garage bases, but the right depth will depend on the ground conditions and base design. Ask your contractor to follow the depth shown on the base plan.
Before pouring the concrete, lay a damp-proof membrane (DPM) and steel mesh over the prepared sub-base. Use a smooth blinding layer where needed to protect the membrane from damage.
The DPM helps stop moisture rising through the slab, while the steel mesh helps control cracking and distribute loads. Raise the mesh on suitable supports and place it in the position shown on the base plan.
Next, pour the concrete into the formwork and spread it evenly, taking care not to move the membrane or steel mesh.
Your contractor should compact the concrete using a suitable method, then level and finish the surface. The base must remain level and match the measurements shown on the plan.
Once the concrete has gained enough strength, lay a single course of semi-engineering bricks over it. The brick course must be level because the garage will rest directly on it.
The bricks raise the timber frame above the slab and help protect it from surface water and rain splash.
Concrete continues to gain strength for several weeks. Ask your contractor and Chart Garages when the base will be ready for installation.
Preparing a garage base involves heavy materials, specialist equipment and careful measurements. For this reason, we recommend hiring an experienced groundwork contractor.
When you order a timber garage from Chart Garages, we provide clear instructions and a detailed base plan for your contractor to follow. This helps them prepare solid, level foundations that suit your chosen building.
Contact our team to discuss your garage and request a quote.
