Many people assume that laying paving slabs on concrete is a difficult task and one that’s better left to the experts. But arm yourself with the right tools and know-how and you can create a patio that beautifully enhances your garden.
Whether you’re mixing the concrete yourself, laying paving on existing concrete, or covering old paving slabs, we’ve put together this step-by-step guide to show you how it’s done. Follow our tips for a durable and attractive outdoor space that’s not only practical, but looks great too.
How to lay a patio onto new concrete
Quick look:
Laying a patio onto concrete or on top of existing paving stones involves seven main steps. These are as follows:
- Mark the area.
- Dig a bed that’s 105mm deep.
- Add a 50mm sub-base layer.
- Mix the concrete – one part cement to six parts ballast.
- Add a 30mm layer of concrete mix.
- Lay the paving slabs, leaving 8 to 10mm spaces between them.
- Fill the joints with the mortar mix.
Tools needed:
Before starting any DIY projects to lay a new or replacement patio, you’ll need to make sure thay you have the following tools to hand. Luckily, you shouldn’t have a problem sourcing these from most high street hardware or gardening stores, and they shouldn’t be too expensive either
- Mattock and shovel
- Flat screeding tool
- String and stakes
- Wheelbarrow or board for mixing
- Spirit level
- Rubber Mallet
- Protective Gloves
- Knee Pads
- Tape Measure
- Rake
- Garden Roller or tamper
- Plate Compactor
- Brick jointing tool
Materials needed:
You’ll also need to make sure you have the following materials in the correct quantities. Certain steps need to be done immediately or soon after the one before, so it’s important to get everything ready beforehand.
How to lay a patio onto new concrete: Step by step guide
Step 1 - Mark the area
The first thing to do is to decide exactly where you would like your patio. It’s worth considering which areas of your garden are shaded – and whether you want to avoid them – and which spots might provide the most privacy.
You should also think about the shape – a curved patio can look beautiful but, as the majority of paving stones come in square or rectangular-shaped slabs, this can be a much trickier thing to lay.
It’s also important to consider what you’ll be using your patio for. Will it be for entertaining, to provide space for an outdoor kitchen, or simply to act as a walkway or entrance to your property? All of this will determine the size and style of your patio.
With important decisions made, you’ll then need to mark the area using string lines and pegs. Once done, make doubly sure its proportions are right for the garden and house so nothing looks awkward or out of place once it’s complete.
Step 2 - Dig a bed
Working slightly outside of the area you’ve defined with the string lines and pegs, dig a 105mm-deep bed. It’s important to remember that the finished surface level of your completed patio should be at least 150mm (two house bricks) below any adjacent damp proof course.
Check that the centre of your site is level with the edges and isn’t rising up or dipping down. Use a spirit level to ensure it’s as flat as possible.
Step 3 - Add the sub-base layer
It’s advisable to lay out around 70mm of uncompacted hardcore to ensure that you’re left with 50mm once it’s compacted. Use either a vibrating plate compactor or a broad plank of wood with a sledgehammer to compact it down to the correct density.
Step 4 - Mix the concrete
You can use a sturdy wheelbarrow to make up your concrete mix, as this way it’s easier to move and dump it in place. If you don’t have one of these to hand, don’t worry, you can use a mixing board instead.
You will need to mix one part cement with six parts ballast and check the bag to see how much water you’ll need to achieve the correct consistency.
It’s a good idea to add the water gradually so you can judge the consistency as you go. Too little water and it won’t mix, too much and it will weaken the mixture. Pull and mix it using a flat shovel or spade.
The concrete should be of a consistency that means it can be poured thickly – if it’s crumbly then it’s too dry and if it’s runny it means it’s too wet. You can keep adding dry aggregate and water until you end up with the perfect concrete consistency.
Step 5 - Lay the concrete bed
Add 30mm of your concrete mix to the site and screed it to ensure everything is packed down and levelled off. It’s important you tamp it down to push the coarse aggregate in the concrete below the surface and consolidate the concrete. This ensures there are no gaps left and water cannot enter and cause damage later on.
Step 6 - Laying the slabs
Now it’s time to start laying paving slabs on your concrete. It’s a good idea to wear knee pads and gloves for this to avoid potential burns from the wet cement. Whether you’ve chosen marble, sandstone or concrete paving, carefully lower your first slab into the concrete.
Keep adding the slabs and ensure there’s a gap of about 8 to 10mm between each stone. Don’t walk on the slabs once they’re laid – you need to wait for the concrete to set, which should take around 24 hours.
Step 7 - Fill the joints
Once the cement has set, you can create the mortar mix. Use four parts sand to one part cement and water – you’re looking to get it to a firm consistency.
Fill the gaps between the slabs with the mix and use a brick jointing tool to pack it in and create a nice smooth finish. Take care not to get mortar on the face of the slabs as this can stain them.
Concrete is fully cured after 28 days – this is when your new patio will be at its full compressive strength.
However, the advice is usually to avoid walking on it for at least 24 to 48 hours to allow it to dry and strengthen and become the beautifully laid patio you’ve put so much effort into creating.
How to lay paving slabs onto existing concrete
Alternatively, you might already have a concrete base in place. If that’s the case, laying pavers on concrete shouldn’t take you too long.
Quick look:
If you want to lay paving slabs onto concrete that’s already in situ, there are five steps you’ll need to follow. These are:
- Prepare your concrete
- Prime the back of the flags with a cement-based primer
- Create the mortar mix – add a 30mm layer
- Lay the paving slabs, leaving 8 to 10mm spaces between them
- Fill the joints with the mortar mix and leave to set
Tools needed:
- Hard-bristled brush
- Flat screeding tool
- Wheelbarrow
- Spirit level
- Rubber mallet
- Protective gloves
- Tape measure
- Brick jointing tool
Materials needed:
Laying pavers on existing concrete: Step by step guide
Step 1 - Prepare your concrete
Use a sweeping brush –to make sure your concrete surface is smooth and clean before you start. Check for any flaking or loose bits and remove them. You can use a hose pipe to help with this step if necessary, but just bear in mind that you’ll need to let it dry completely before continuing.
You’ll need to ensure there are adequate falls in place to allow surface water to drain off, and the finished surface level should be at least 150mm (two house bricks) below any adjacent damp proof course.
Step 2 - Prime time
Spread a cement-based priming product on to the back of the slabs. This will ensure they’re laid as securely as possible.
Step 3 - Mix the mortar
Using four parts sand to one part cement and water, create a mortar mix. Take care to add just the right amount of water for a firm consistency – it should be damp, but not wet and runny. Put down a 30mm layer of the mix and ensure you have an even, smooth base, ready for your slabs.
Step 4 - Lay the slabs
Carefully laying the pavers into the mix, ensure that you’re leaving a 8 to 10mm gap between each one and tap them lightly into place with a rubber mallet. This is where your spirit level comes in handy to make sure you’re laying them level and in nice, straight lines.
Step 5 - Fill the joints
Put the finishing touches to your project by using the mortar mix to fill in the spaces between the slabs. Use a brick jointing tool to pack it in and create a smooth finish, taking care not to get mortar on the face of the slabs – you don’t want to be left with permanent stains that will ruin the overall effect of your hard work.
You’ll need to leave the paving to set for at least 24 hours before walking on it (or longer in wet weather).
Prefer to have your patio installed by an expert? Get in touch today or find your nearest Marshalls-accredited installer.
Download our guide to the most popular garden patio paving patterns and see for yourself how a small patio doesn’t have to mean a small sense of character.
How to cover old paving slabs
You may wish to save yourself some time and simply refresh your tired looking patio with some fresh paving slabs. To do this, you don’t always need to uplift the old slabs. Here’s our method for covering old paving slabs with new ones.
Quick look:
If you’re thinking about laying new paving stones on top of existing ones, there are eight steps you’ll need to follow. These are:
- Prepare the surface
- Measure and markup the area
- Lay the first base of gravel
- Level out with a layer of sand
- Lay the pavers
- Cut pavers for any gaps
- Cement the edges
- Finishing touches
Tools needed:
- Tape measure
- Spirit level
- Rubber mallet
- Shovel
- Wheelbarrow
- Protective gear (gloves, goggles, etc.)
Materials needed:
Step 1 - Preparation
Before you begin, remove any debris from the patio. Clean the area thoroughly, ensuring that there is no dirt, grit, or weeds left behind. Level the ground by removing any high spots and filling in any low spots with soil or sand.
Step 2 - Measuring and marking
Measure the area of the patio to determine how many paving slabs you will need. Make sure that you take into account any curves or angles in the patio. Mark the edges of the patio with string or chalk lines.
Step 3 - Laying the base
Add a layer of gravel to the patio to create a solid base. Use a shovel to spread the gravel evenly, and then use a rake to level it out. Use a spirit level to ensure that the base is even.
Step 4 - Laying the sand layer
Add a layer of sand over the gravel base to create a smooth surface for the paving slabs. Spread the sand evenly using a shovel, and then use the rake to level it out. Again, check that the layer is level using a spirit level.
Step 5 - Laying the paving slabs
Begin by laying the first row of paving slabs, starting at one corner of the patio. Use a rubber mallet to gently tap the slabs into place. Continue laying the slabs, working your way towards the opposite end of the patio. Use a spirit level to ensure that the slabs are level.
Step 6 - Cutting the paving slabs
If you need to cut any of the paving slabs to fit around the edges or curves of the patio, use a paving stone cutter or a circular saw with a diamond blade. Make sure to wear protective gear when cutting the slabs, including a face mask so you don’t breathe in any dust created.
Step 7 - Filling the gaps
Once all of the slabs are laid, use a brush to sweep sand into the gaps between the slabs. This will help to stabilise the slabs and prevent them from shifting. Use a broom to remove any excess sand.
Step 8 - Cementing the edges
To secure the edges of the patio, mix cement in a wheelbarrow, then, use a trowel to apply the cement along the edges of the patio, making sure that it is flush with the paving slabs. Smooth out the cement using a trowel or a float.
Step 9 - Finishing touches
Allow the cement to dry for at least 24 hours before walking on the patio. Once it is dry, you can add any finishing touches, such as plants or outdoor furniture.
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