Shed Base Calculator
Compare foundations for timber and metal garden buildings.
Material Summary
The Foundation of a Lasting Shed
Drainage & Stability
A shed is a significant investment, but without a level, well-drained base, it will quickly deteriorate. A poorly built base leads to sticking doors, leaking roofs, and rising damp in the floor.
Our **shed base calculator** allows you to compare the most popular foundation methods in the UK, ensuring your garden building remains square and dry for decades.
Comparison Matrix
The 'Spirit Level' Test
The most important tool during your base build is a long spirit level. If your base is just 10mm out of level across an 8ft span, the top of the shed walls will be significantly out of alignment, making the roof impossible to fit correctly.
Check for level in multiple directions: across the width, down the length, and diagonally from corner to corner.
Weed Membranes
Always lay a heavy-duty geotextile weed membrane under your base. This prevents weeds from growing up through your base and trapping moisture against the shed's floor joists.
Sub-base Compaction
If you are using MOT Type 1, you must compact it using a 'wacker plate' (vibratory compactor). Loose hardcore will settle under the weight of the shed, leading to an uneven base within months.
Pro Tip: Air Gap
If using a concrete or slab base, place the shed on **pressure-treated timber runners** (38mm x 50mm). This creates a 50mm air gap between the cold, damp concrete and the shed floor, dramatically extending the life of the building.
Shed Foundation FAQ
Project Disclaimer
Material estimates are based on standard shed dimensions. Large log cabins, workshops with heavy machinery, or bases on exceptionally soft or sloping ground will require a more substantial structural design, often involving reinforced concrete rafts.