How to Lay a Shed Base

Welcome to our step-by-step guide on how to lay a base for garden sheds, using our aggregates that we sell and deliver to you.

In this step-by-step guide you will learn how to lay a ground area down either with paving slabs or simply concrete, so that you can transform an area of your garden into a space for garden sheds, greenhouses, or out-houses/summer houses. Say goodbye to unwanted grass areas that don’t get used and say hello to your new outside space that’s practical and stylish.

Tools List

• Safety goggles
• Protective gloves
• Knee Pads
• Builder's line
• Builder's square
• Shovel
• Wheelbarrow
• Tape measure
• Straight-edge rake
• Wooden spacers
• Club hammer or Rubber mallet
• Earth rammer or Vibrating Plate Compactor
• Spirit level
• Bucket
• Soft brush
• Trowel
• Watering can
• Hammer
• Large screed

Materials List

• Wooden marker pegs
• Sub-base - MOT type 1 hardcore
• Mortar/concrete mix (5:1 sharp sand & cement) - (aggregates)
• Paving slabs (or bricks if that’s what you’re using)
• 5mm spacers
• Timber offcut (if using concrete to make the patio, you’ll need 5 timber beams/planks - 4 to make a square base, 1 to bind the square in the middle)
• Large headed nails or screws
• L bracket
• ??? Cement mixer - hire if really big concrete surface
• Plastic sheet and bricks

Health & Safety

• Don’t work aloneIt’s a two person minimum job
• ChildrenMake sure that children are not near the workspace and don't let them handle the tools
• ChemicalsAlways read labels of hazardous materials and wear protective clothing like gloves and goggles
• LiftingAlways bend at the knee, not hunching your back over - don’t lift heavy items alone
• Power toolsAlways wear safety equipment and understand how to use the tools properly first

Method

Please note: If laying the patio directly next to a property, you’ll need to create a slope away from the property walls. So on the garden side, dig a slight slope away from the property, so that moisture travels that way through the soil. The sub base will need to be level still, so use more on the slope side. Use wooden pegs and a spirit level to aid you in making the slope. 

Step 1: Preparing for the sub-base if using paving slabs

• If you’re using paving slabs that are a different size, we’d recommend that you do a practice run, laying out all the slabs into the shape that you desire and taking a photo or numbering the slat
• If using paving slabs the area will need to be bigger than the shed itself, so there is enough room to walk around the shed on the patio area. 
• You’ll now need to mark out the area for where you want the base for the shed to be. To do this, take your wooden pegs and hammer one in each corner of the area and use your builders line (or string) to go around all of the pegs, creating the shape outline that you want the shed base to be  
• Check the shape is even/square by using your builders square to check the angles of the corners. A tip, if you measure the diagonals of the builders square and make sure every corner is the same length, then it’ll be perfectly square. 
• You’ll now need to measure how far to dig down in the desired area giving enough room for the sub-base, mortar mix* and paving slabs themselves
• 50mm for sub-base + 50mm for mortar mix + the slabs (usually around 25mm) = 125mm (12.5cm)
• Using a spade/shovel dig down to the correct depth. Use a ruler or measuring tape to make sure it’s the correct depth
• You can now remove the wooden pegs and builders line

What is a mortar mix, how to make it and what types of aggregates are there?

Aggregates are simply a variety of materials used to mix with cement and water to make concrete, the different types that you could use for preparing a shed base are ballast (a mixture of sharp sand and gravel), MOT type 1 hardcore or building sand. It’s made in a ratio of 5:1 (aggregates to cement) and whatever amount of water you need according to the cement packaging. You can collect aggregates from us at Concrete 247. 

You can learn more about aggregates or you can speak to a member of the team.

Step 1a: Preparing for the sub-base if using concrete

• Make a square/rectangle frame that matches the desired size of the patio using your timber beams. 
• You’ll need to nail them together or use an L bracket and screw in place, as well as one timber beam going through the centre (horizontally), this may require you to saw them to the correct length
• The timber framework will need to fit inside the dug-out area with spacing around the outside and the depth slightly coming above surface level
• Check the shape is even/square by using your builders square to check the angles of the corners - a tip, if you measure the diagonals of the builders square and make sure every corner is the same length, then it’ll be perfectly square
• Put aside the framework for a while
• You’ll now need to mark out the area for where you want the base for the shed to be. To do this, take your wooden pegs and put one in each corner of the area and use your builders line (or string) to go around all of the pegs, creating the shape outline that you want the shed base to be  
• Check the shape is even/square by using your builders square to check the angles of the corners. 
• You’ll now need to measure how far to dig down in the desired area giving enough room for the sub-base and concrete
• 75mm for sub-base (MOT hardcore) + 75mm for concrete = 150mm (15cm)
• Using a spade/shovel dig down to the correct depth. Use a ruler or measuring tape to make sure it’s the correct depth
• You can now remove the wooden pegs and builders line

Step 2 - Laying the patio sub-base

• Mark the sub-base depth on a few wooden pegs and hammer them around the dug out hole, this is so you can see where to fill the sub-base to. 
• Using a wheelbarrow, tip the sub-base/MOT type 1 hardcore into the area, so that it’s just above the marked area on the pegs.
• Once the area is filled, remove the pegs and use a rake to even out the sub-base
• Put on all your protective gear, including industrial ear muffs if you have them
• Follow the instructions from your vibrating plate or earth rammer and go over the sub-base area with the power tool, as if you were mowing a lawn, until all of the sub-base is flattened, smooth and even (use spirit level to check)

If using concrete, please skip to step 5

Step 3: Laying the mortar mix (for paving slabs)

• Your mortar mix or ‘blinding coat level’ is where you take the Aggregates that’s right for your job (sharp sand, ballast etc.) and mix with cement
• Remove the pegs and builders line that you laid out at the beginning
• Mix your aggregates with the cement in a ratio of 5:1, and then add the amount of water that’s stated on the cement package. It’s probably best to do this in the wheelbarrow
• Don’t pour the cement over the whole area, instead lay just enough to do one slab at a time and use a trowel to level out
• Dampen the bottom of the paving slab, ideally with a paint brush and water
• Lay the slab over the cemented area and tap into place with your rubber mallet
• Check it’s level with the spirit level
• Use wooden spacers to create a slight gap between each slab
• Repeat these steps until all slabs have been laid
• Remove all wooden spacers and with a watering can, wet between all of the joints/ridges of the slabs 
• Wait for this to completely dry

Step 4: Sealing the slabs (jointing)

• In a bucket, mix a ratio of sand (5) to cement (1) (5:1) to create a dry mix
• Fill all the joints to the top with the dry mix and brush off the excess 
• Push down the dry mix in the joints, add more and brush the excess again
• Smooth it out with the back of the trowel and leave the patio to completely dry and then the patio is complete

Step 5: Filling with concrete

• Make sure you are wearing all protective gear - gloves, boots, googles - wet cement can cause burns, so always wear gear and wash your hands regularly
• Avoid concrete drying on your tools
• First you will need to take your timber frame that you made earlier and align it on top of the sub-base so that there is some space on the outside of the dug-out hole
• Mix your concrete in a mixer or by hand in a wheelbarrow (depending on how big your job is, this will alter your method choice) - this will be 5 parts sharp sand or ballast with 1 part cement and the amount of water required (see cement packaging)
• Wet the sub-base with a watering can
• Gradually pour the concrete onto the sub-base bed (this will require two people) and level it out as you go along with a shovel - work in small sections rather than the whole area
• Use the shovel and stab the concrete up and down with it, particularly around the edges, to remove air bubbles
• Use a rake or the shovel to spread out the mixture and smooth it
• The concrete will need to be about 2cm above the timber frame
• When all concrete is laid - with a helper, glide a screed or timber/tamping board along the top of the concrete (the screed/board will need to be longer than the edges of the framework so it can sit on top of this as you glide it)
• This should create a smooth top but if not repeat the process (add more concrete if there are dents)
• If you’re happy with the finish of the concrete, go along the edges with a trowel, neatening any unevenness

Step 6: Protecting the patio as it dries

• Create four stacked-bricks along each side of the patio so that they are several inches taller than the patio
• Take a timber and line it up over the bricks so that it goes down the centre of the patio
• Place a plastic sheet over the patio, so that it goes over the bricks and timber, not touching the patio surface
• Way the plastic down with more bricks and set to dry (a concrete patio will take approx 2 days)

Step 7: Removing the concrete form (ignore if used paving slabs)

• After the concrete has had plenty of time to dry, the timber frame that was made to use as a form for the concrete now needs to be removed 
• Take a hammer or rubber mallet and tap all of the sides of timber, to loosen it up a bit
• Remove any screws or nails that were used to put the frame together
• The wood should have come loose by now, so use the end of the hammer to insert into any dents between the wood and the concrete and pull the wood off (carefully)
• Repeat until all the form is removed

There you have it

So there you have it, a step-by-step guide on how to lay a base for a shed. With this guide you should now be able to create a patio/ground area that is the perfect fit for your garden shed, summer house or greenhouse. 

Should you seek any further professional advice on laying a shed base or what aggregates to use please do give Concrete 247 a call and we’d be more than happy to help.

We help customers based in the South East areas of Southampton, Portsmouth, Eastleigh, Totton, Fareham, Winchester and other surrounding areas with their building projects and enquiries. Find out more about our delivery and collection services of concrete, pumps and aggregates by giving us a call.