Laying a patio, or paved area, can be a great way to add a practical, low-maintenance space for relaxation and entertaining in your garden.
It can be time-consuming getting the base ready and laying the slabs, however the techniques used are relatively simple and it's possible to complete a small project in a weekend. It’s recommended that you get someone to help as the slabs can be heavy so much easier with an extra pair of hands.
1. Prepare the base of your patio
The first step in creating your new patio is marking out the space.
You'll also need to calculate and mark out the fall. The fall is a slight slope across a paved area that helps surface water to drain away easily. A patio is still level with a fall as the gradient is so gradual.
Step 1
If possible, dry lay your slabs to check that your measurements are correct.
Lay out the paving slabs in the desired pattern, either where you plan to build your patio or on a clear, flat area. Allow for your preferred joint size between each slab.
Measure the length and width of the paving area to confirm the final dimensions of your patio. Move the slabs out of the way, making a plan on paper of what goes where so you can put them back in the same location.
Step 2
Mark out the area for the sub-base using wooden pegs and a builder’s line. Ideally add an extra 5 to 10cm to every edge of the patio measurement. This will make the sub-base slightly bigger than the finished patio giving it a more secure foundation.
Place a wooden peg in each corner and run a builders line between each peg to provide a straight edge for the sides of the patio. Use a builders square to make sure the corners are square.
As a final check, measure the diagonals to make sure they are the same length. If they're not, measure each side again and adjust until your diagonals match.
Step 3
Calculate the fall for your patio, using the final dimensions confirmed at the end of step 1.
The ideal fall is dependent on the type of paving slabs being laid.
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If using textured paving slabs – the ideal fall for a patio is 1 in 80. That is a 12.5mm drop in level per metre.
If using flat or smooth paving slabs - aim for a fall that is 1 in 60. That is a 16mm drop in level per metre. These paving slabs require a slightly steeper slope as they’re more likely to get slippery if surface water doesn't drain off quickly.
To calculate the fall:
Multiply the required fall (e.g. 12.5 or 16mm) by the length of the sloping side of the paved area in metres (m). This will give you the total difference in height required between the highest and lowest point of the patio.
IMPORTANT: If building a patio next to a house, garage or outbuilding, the paved area should slope away from the walls. You can choose the slope direction if there are no walls on any side.
Step 4
Cut the turf into strips with a lawn edger (to give a neat line) and lift using a spade.
Roll up and save some of the turf in case you need to fix any gaps between your existing lawn and the paved surface.
Step 5
Calculate the necessary depth for the sub-base.
For a depth of 215mm you can follow the below guide:
100mm of sub-base (compacted MOT Type 1 granular hardcore)
a thin blinding coat of sharp sand or all-in-ballast
a 50mm layer of mortar
the paving slab
All of these layers add up to give the necessary depth for digging.
Once calculated, dig the area to the correct depth using a spade.
Once your area is marked out and the turf is removed you should get a strip of wood to check your edges using a spirit level. When you’re happy that all is ok you are ready to lay your sub-base.
Tip in the hardcore using a wheelbarrow to fill the sub-base to just above the wooden pegs.
Compact with a plate compactor or roller ensuring the surface is level.
Cover the surface with a thin layer of sharp sand and rake level. This is your blinding coat.
Remove the corner pegs and lines.
Although the fall has already been set in the sub-base, it’s important to run a set of builders lines marking the perimeter of the patio and the top edges of the paving slabs. This will help you maintain the correct slope when you lay the slabs.
Laying your first slab
Paving slabs are bedded in a mortar mix with four parts sharp sand to one part cement. Measure your quantities using a shovel or a bucket - for example, four buckets of sand for every one bucket of cement. Mortar will need to be used within two hours of being made (in hot weather you’ll have less time), so mix as much as you think you can use in that time.
A cement mixer will make short work of mixing, but you can also mix smaller quantities by hand on a mixing tray.
Starting in one corner of the sub-base area (at the highest point), lay about 60mm of mortar on top of the sub-base. You'll only need to lay enough mortar for the first slab.
Wet the back of the slab with a brush, ready to be laid – this will improve adhesion and make it easier to slide into position.
Use a piece of timber and a club hammer or rubber mallet to tap the slab into position. Take great care not to crack the slab.
Fill any gaps under the slab with mortar, cutting it flush with the edge as you go with a trowel.
How to cut paving slabs
For some paving projects you'll need to cut paving slabs. An angle grinder fitted with a stone-cutting disc will make light work of the cuts. Mark the cutting line in pencil on both the surface and edges of the slab and use the angle grinder to follow this until you have a clean cut. Once you have positioned the first slab, laying the rest of the slabs is quite straightforward.
Once complete, leave the mortar to dry for at least 48 hours. If bad weather is forecast after your paving slabs have been laid, cover the patio with a tarpaulin to protect against rain and wait until a dry day to finish your project.
Remove the spacing pegs once the mortar is dry.
Jointing
Jointing is the final step in completing your patio. It's the process of filling the gaps between the paving slabs to provide a firm, level surface.
Depending on the size of the joints between the slabs, different techniques are used to ensure a hard-wearing finish.
For joints less than 5mm wide
Using a soft brush, sweep kiln-dried sand into the joints between the slabs.
Finish off by sweeping the surface of the whole patio to ensure that it's free of loose sand.
For joints 5 to 10mm wide
Medium-size joints are best finished using a dry mixture of sand and cement. The addition of cement leads to a firmer finish and the mixture will set as moisture in the ground is absorbed over the first few days.
Mix one-part kiln-dried sand with one part cement in a clean bucket.
Gently sprinkle the mortar mixture along the joints. Brush in using a soft brush.
As you work, brush away any excess mixture from the surface of the slabs to prevent staining from the cement.
Compress the joints using a jointing tool and keep adding the mix until full.
For joints over 10mm wide
For larger joints, use a wet mortar mixture.
Mix four parts building sand and one part cement in a bucket, adding clean water until you achieve a slightly moist, smooth, damp consistency. Add the water slowly to the mix to help avoid creating a wet or sloppy mortar that runs easily off a trowel or jointing tool.
Work the mortar into the joints using a trowel. Push the mix down firmly into the joints with a jointing tool, and repeat this process until the joints are full, compacting and smoothing as you go.
Carefully brush away all of the excess mortar from the slabs, as the cement could stain them. Use a damp sponge to do this as you work on one joint at a time.
