Gravel pad foundation

Is it right for your shed?

Best fit: A framed storage shed on a reasonably level, well-drained site.

What goes under it? The ground layers

The explanation runs from the ground upward. Callout labels in the drawing identify the visible parts; some thin layers are enlarged for clarity.

1. 1

   Firm subgrade

   Remove vegetation, roots and organic topsoil. Correct soft spots before placing aggregate.

2. 2

   Separation layer

   A suitable geotextile can keep stone from mixing into fine soil; it is permeable and is not a waterproof membrane.

3. 3

   Compacted aggregate

   Place the specified stone in manageable lifts. Thickness and grading depend on soil, drainage and the loads.

4. 4

   Bearers and floor

   Set the approved skids or support frame on the finished pad. Leave a visible drainage margin around the shed.

Materials and preparation

Use the quantities and specifications from your actual layout. Before ordering, resolve the pad footprint, support locations, finished floor height and the drainage route.

• Specified crushed aggregate and any separation geotextile
• Edge restraint where needed; ground-contact timber if used
• Compactor, level or laser, stakes, string and excavation tools

Useful planning: choose the shed location and check permit requirements.

Build sequence

This sequence explains the order of work. Use it alongside the foundation design and the instructions for your chosen products.

1. Step 01

   Set the height before digging

   Mark the shed, pad edges and finished floor level. Include door access, cladding clearance and the route roof runoff will take. A pad sunk into clay can become a collection basin even when its stone looks clean.

2. Step 02

   Prepare a uniform formation

   Excavate organics across the pad. Check the exposed ground for pumping or soft pockets. Do not bury a weak spot beneath extra loose stone; improve it using a site-appropriate method first.

3. Step 03

   Separate and contain

   Lay specified geotextile without tearing it and secure the edges. Install any low perimeter restraint square and level. A landscape timber border retains a shallow pad; it is not automatically a retaining wall for a hillside.

4. Step 04

   Place and compact the stone

   Build the pad in lifts suited to the compactor and aggregate. Check elevations across the entire footprint, including the future skid lines. Avoid rounded decorative gravel as a substitute for a specified compactable base.

5. Step 05

   Check the delivered shed support

   Confirm that every bearer has its intended support and the frame is square. Install the separate anchoring system, then finish the surrounding grade so runoff leaves the pad without eroding its edges.

Mistakes to avoid

• Using gravel to cover grass rather than removing it.
• Assuming water can disappear into impermeable clay.
• Letting an unsupported skid bridge a low area.

Inspection and maintenance

After heavy rain and the first seasonal freeze-thaw cycle, inspect the perimeter for erosion, standing water and low spots. Keep soil, leaves and mulch away from the bearers. Investigate settlement before repeatedly adding stone under one corner.

When to choose a different base

Choose gravel when you need a practical base for an already designed floor system. Choose a slab when the floor itself must be hard and washable, or piers when a suitable level pad would require excessive fill.

Common questions