Building the perfect shed base and sub structure

Ensuring your shed has a solid footing, suspended above the ground will help protect your shed from rotting, warping or cracking. The most important of all, is to ensure your shed base is dry and able to drain freely.


There are many ways that this can be achieved, from a full excavation and replacement with hardcore and sand to installation of a simple plastic grid shed base.

Our IBRADECK grass grids can also be used to raise your shed up off of the ground by 3.5cm, with enough flex and strength to hold the weight of your shed and contents.

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Building the Perfect Shed Base

Installation - excavation method

Using the excavation method, you will need to remove at least 1 1/2ft of topsoil to be replaced with hardcore and sand for the full span of the shed to sit on top. You may also want to dig a channel off the outside of the excavation for rain water run off.

The shed floor joists should then be spaced every 12" to 24" apart depending on joist size, joist material and floor material . Ideally, a composite or plastic joist would be the best solution but practically, a 2-3" tanalised/treated timber joist would be best. Thinner shed floors, made in the standard OSB should be supported with more joists, roughly 12" apart.

Installation - plastic shed base method

Using the plastic shed base method, you don't need to carry out any excavations. Simply mark out the area you wish to place the shed upon, level it with sand and line with a high quality, permeable landscaping fabric such as FABREX-100. This keeps weeds down, allowing water to drain through the bottom whilst also providing an element of damp-proofing from ground suface water.

With our demonstration shed, we added 4mm shingle into the lattices of the grids to provide a striking finish. We also considered that long term, the shingle in the grid would also act as a natural filter for rain water to run through.

Often people forget about their sheds and come back to find mice living under their sheds. With plastic grids in-filled with gravel up to the level of the bottom of the shed side panel, mice will find it hard to get in or under the shed. This also helps increase the lifespan of your shed.

Are you looking for a new shed? Have you thought about the shed sub base? Send us a message to ask our advice!