Garden preparation for shed installation

In the UK, our heavy rainfall and varying soil types mean that simply "plonking" a shed on the grass is never an option. Professional garden preparation ensures the site is excavated correctly, protected against rising moisture, and engineered to support the specific weight of your chosen building.

What Does the Work Involve?

• Site Clearance: Removing existing turf, plants, roots, and surface debris from the intended footprint plus a 300mm "splash zone" perimeter.
• Excavation: Digging out the area to a depth of 100mm–200mm, depending on the chosen base type (e.g., concrete vs. paving slabs).
• Levelling and Drainage: Ensuring the sub-base is perfectly level while accounting for natural garden run-off to prevent water pooling against the shed.
• Membrane Installation: Laying a heavy-duty geotextile weed membrane to prevent growth and separate soil from the sub-base materials.
• Sub-base Compaction: Spreading and mechanically compacting MOT Type 1 hardcore or sharp sand to create a non-shifting foundation.
• Base Construction: Installing the final surface, which could be a solid concrete pour, laid paving slabs, or a timber bearer frame.
• Waste Removal: Bagging or skipping the "arisings" (excavated soil and turf) for legal disposal off-site.

Typical Costs

Prices for garden preparation vary based on the size of the shed and the amount of "muck away" required. A sloping site will significantly increase costs due to the extra excavation and retaining work needed.

Factors affecting the final quote include "hand-dig" vs machine access, the distance from the work area to the skip, and whether you require a concrete pour which involves higher material costs and curing time.

How Long Does It Take?

• Small Timber or Slab Base: 4–6 hours. This is usually a one-day job for a single landscaper, including clearance and levelling.
• Medium Concrete Base: 1–2 days. Day one involves excavation and shuttering; day two involves the pour and finishing.
• Sloping or Overgrown Sites: 2–3 days. Significant time is spent clearing brambles, removing old structures, or building sleepers to retain a level tier.

DIY or Professional?

While clearing turf is a straightforward DIY task, achieving a perfectly level finish is harder than it looks. A 5mm error across the base can result in shed doors that won't close and a roof that doesn't sit flush, leading to leaks.

Professional landscapers have the plant machinery (like plate compactors and mini-diggers) to ensure the ground won't sink under the weight of the shed over time. If you plan to run electricity to the shed, you must use a professional to ensure the base preparation accounts for armoured cable ducting in compliance with BS 7671 (Part P) regulations.

Expert Tip: Always ask your landscaper to install the base slightly larger than the shed floor, but ensure the shed itself has a "drip edge" so rainwater doesn't sit on the base and rot the bottom timbers.

Choosing the Right Tradesperson

• Check Qualifications: Look for landscapers who are members of the Association of Professional Landscapers (APL) or the British Association of Landscape Industries (BALI).
• Waste Licensing: Ensure they hold a valid Environment Agency Waste Carrier Licence; otherwise, you are legally liable if your garden waste is fly-tipped.
• Specific Experience: Ask if they have experience with the specific base type you want (e.g., "rapid grids" vs. traditional concrete).

Questions to ask:

• "Will you be using MOT Type 1 for the sub-base, or just sand?" (Type 1 is superior for stability).
• "How do you plan to manage drainage and water run-off?"
• "Does your quote include the cost of skip hire and soil disposal?"

UK Regulations

• Permitted Development: Most sheds don't need planning permission if they are under 2.5m tall (at the eaves) and take up less than 50% of your garden.
• Boundary Rules: If the shed is within 2 metres of a boundary, the total height is usually restricted to 2.5 metres.
• Building Regulations: Generally not required for small sheds (under 15sqm), but if the shed is between 15sqm and 30sqm, it must be at least 1m from any boundary.
• Paperwork: Expect a written quote, a waste transfer note (if soil is removed), and an invoice clearly stating any guarantees on the levelling work.

Common Problems

• Subsidence: If the ground isn't compacted with a vibrating plate, the shed will sink unevenly over the first 12 months.
• Rising Damp: Omitting a weed membrane or DPC (Damp Proof Course) allows moisture to travel from the soil into the floor joists.
• Poor Airflow: Setting a shed too low or surrounded by high grass prevents air from circulating underneath, leading to dry rot.
• Hidden Services: Hitting water pipes or electric cables during excavation. Always check "dial before you dig" or use a CAT scanner.

Frequently Asked Questions

Do I really need a concrete base for a small shed?

Not necessarily. For sheds up to 8x6ft, a well-laid paving slab base or a timber pressure-treated frame on "pro-base" plastic grids is often sufficient and much cheaper than concrete.

Can I put my shed on existing decking?

It is generally discouraged. Decking is designed for foot traffic, not the concentrated, static weight of a shed and its contents. The lack of airflow can also rot both the deck and the shed floor.

How much space should I leave around the shed?

Ideally, leave at least 18 inches (450mm) of space on all sides. This allows for air circulation and gives you enough room to apply wood preservative or repair panels in the future.

What is the best base for a plastic or metal shed?

Plastic and metal sheds are lightweight and prone to condensation. A solid concrete slab with an integrated damp-proof membrane is highly recommended to provide an anchor point and reduce moisture rise.

My garden is on a steep slope, can I still have a shed?

Yes, but it requires more prep. A landscaper will likely build a "cut and fill" level area using timber sleepers or a brick retaining wall to create a flat plateau for the base.

Will the landscaper also assemble the shed?

Some landscapers offer a full supply-and-fit service, but many specialise only in the groundworks. Always clarify if assembly is included or if you need to hire a separate handyman.