How to lay a paving slab base

Equipment required

To prepare a paving slab base for a garden building you will need: a tape measure, four wooden pegs, a ball of string, spade, a large bucket or similar for mixing cement in, garden rake, rubber mallet, tri-square and a spirit level. 

You will also require some building sand, also called sharp sand, and a 25kg bag of standard all-purpose cement. (The sand to cement ratio required will be 8:1.)

Step 1 - Measure and mark

Using the tape measure, mark out the area for the base, making it 5cm (2") larger than your garden building on each side. Hammer in the pegs and run the string between them, then make sure the corners are completely square by measuring them with the tri-square to ensure they are at a 90° angle to each other.

Step 2 - Dig marked area

Dig out the ground in the marked area to around 65mm (2.5") deep and remove the pegs and string line. You can make the hole a little shallower than this if you would prefer the base of your building to stand slightly raised from the ground to help with drainage.

Step 3 - Mix sand and cement mix

Stir together one part cement to eight parts building sand for a dry sand and cement mix. 

You don't need to add water - the damp in the atmosphere will create the curing needed for the cement content. 

Step 4 - Spread sand and cement mix

In the excavated area, spread the mixture evenly to a depth of about 40mm (1.5") and rake thoroughly, ensuring it's completely level.

Step 5 - Lay paving slabs

Starting from a corner and working outwards, carefully lay out the paving slabs and tap each one down with a rubber mallet to make sure it's secure.

Step 6 - Check slabs are level

This is the most important part of the process! Check that the slabs are square and firmly butted together, and use a spirit gauge to make sure that they are absolutely level - otherwise your building will eventually warp. Finally, brush off any excess sand and cement mix which could make the base uneven.