Every garden needs a shed. It’s the perfect safe, dry storage solution for your gardening equipment, furniture, outdoor toys, BBQs and more.
A great shed is also a handsome natural timber addition to your outdoor space, blending beautifully with your lawn, trees, shrubs, flowers and fencing. So, it’s worth taking the trouble to build a shed that’s attractive and sturdy as well as useful — and that has to start with the foundations.
Without a firm and level base, your new outbuilding may start its life looking fresh, but it’ll be unusable before long.
Alternative types of shed base include timber (aka a portabase), plastic, and paving stones. However, in this article, we’re going to focus on the most reliable option: preparing and pouring a solid concrete slab.
You can hire all the tools and equipment you’ll need to lay a concrete base for your shed from the HSS range, so we thought we’d complete the service by providing instructions as well. Here’s our eight-step guide to laying a concrete slab worthy of your new shed-shaped pride and joy.
Step 1: Measure up and mark out
Once you’ve decided on the location, start by marking out the area for the slab. Make it wider and longer than the shed will be, and allow extra space for the formwork — that’s the technical term for the wooden frame that will go around the edge of the area to keep the concrete in place. Drive a wooden peg into the ground at each corner and run a taut length of string between them. Make sure the corners are square by measuring both diagonals. If they’re not precisely the same, you need to adjust.
Step 2: Dig out the base area
Below slab level, you’ll lay a 100mm sub-base and a damp-proof membrane. Therefore, you need to dig a level-bottomed pit 100mm deep. Be sure to remove all grass and other vegetation, stones and debris, then compact the earth. A micro excavator will make light work of the digging.
Step 3: Lay the sub-base
You can’t lay a concrete base directly onto soft ground, so a hardcore sub-base is essential. MOT Type 1 hardcore is the ideal material to choose. It’s the recommended sub-base for laying tarmac on roads and is readily available in jumbo packs from DIY stores and trade suppliers.
Once your gravel sub-base is in place, thoroughly compact it using an HSS light vibrating wacker plate. Spread a layer of sand on top to prevent the sub-base stones from puncturing the damp-proof membrane.