Laying a Patio in your garden successfully requires planning and preparation, along with a solid foundation and a bit of hard graft. This guide will explain how to lay a simple paving slab patio that will look fantastic and last for years with little or no maintenance. The advice and tips shown here can be applied to a patio of almost any size and shape.
Mark Out Your Patio Size
Plan where you want to lay the patio and use wooden pegs and string to mark out the shape. Use the size of your chosen patio slabs to work out the total length of each edge. This is obviously much easier to do for a regularly-shaped patio that will use slabs of one size.
Alternatively, you can lay out the slabs (dry) in your required pattern, mark the edges and corners, and then move the slabs out of the way.
Patios usually butt up against a wall of a house, so you may be able to use this as a guide to laying out the shape of the patio area. If the patio needs to have square corners, use a builders square to check that they are all at 90 degrees.
Marking out the patio before you start to dig out is important. It lets you see how big your proposed patio will be and see if there will be any obstructions.
Digging the Patio Foundations
If you want your patio to last for years and remain in good condition (and who wouldn’t?) it is important to properly prepare the foundations.
- Using the string lines as a guide, mark around the edge of the patio area with a spade.
- Cut down through any turf or soil so that there is a clear line all the way around the edge. Once this is done, you can remove the pegs and string.
- Dig out the turf and soil to a depth of around 100mm, plus the depth of your chosen slabs and a couple of centimetres of mortar.
- Keep the sides of the foundation hole as straight as possible if you will be lining the hole with treated timber boards (optional, but recommended).
Lining the Patio Foundation Hole (Optional)
Lining the edges of the foundation hole can really help to achieve a clean finish. The boards will also protect the edge of the slabs, and prevent the surrounding soil from slumping into the gaps beneath them.
- Cut pre-treated timber boards that are the same depth as the sides of the foundation hole and use them to line the edges. The timber should be exactly the same depth or very slightly lower than the surrounding soil. Use a level to make sure that the edging is level and hold the timber in place using wooden stakes.
- When all the timber edging is level, use a mallet to lower the edge furthest away from the house (or wall) so that you create a very slight gradient which will allow water to drain off the patio and away from any solid structures.
- Remember to lower one end of the timber on each side so that they slope down to meet the slightly lowered edge.
Laying a Hardcore Base for the Slabs
The next job is to lay and compact the base of hardcore material which will create the solid foundation for the mortar and slabs. Without a good, solid hardcore base, the patio will be much more likely to shift and sag.
- Check that the foundation hole is evenly excavated and then start to add the hardcore material. Hardcore can be building rubble, made up of bricks, blocks, stone, sand, and other materials. Make sure that there is no wood, metal, or plasterboard mixed in with the hardcore as you add it to the hole.
- Distribute the hardcore evenly over the area to a depth of around 100mm and level it off with a spade or rake. Use the timber edging as a guide and create a slight slope away from the house.
- If the area of the patio foundation is large, you could hire a small mechanical compactor to evenly flatten the hardcore. If you don’t have access to a compactor, you will have to do your best with the flat of a spade or a homemade compactor made of a flat square of wood attached to a handle.
- If the surface of the hardcore base is still rough after compacting it, lay a thin blinding layer of sand on top to even it up.
If needed, add more hardcore material to fill any dips or large holes in the surface of the patio foundation layer.
Mortar Mix for Laying a Patio
The most common mortar mix used when laying paving slabs for a patio is 4:1 (four parts sharp sand to one part cement.) Make the mix dry enough that it stands on the trowel without slumping.
We recommend mixing up a small amount of mortar in a clean bucket. At least until you are confident in laying slabs at a decent speed.
You can use this mortar mix ratio if you are planning to lay a full bed or use the five-point mortar method. The five-point method is when you add four dabs of mortar at the corners of the slab and one in the middle. This method can be quicker and use less mortar but is unlikely to provide as stable a base as when laying a full mortar bed.
Laying the Patio Slabs
It is a good idea to lay the slabs dry, allowing for mortar joints, so you can plan out how many slabs need to be cut, etc. The slabs can be laid in any pattern you like, even as a simple grid, but something like a brick-bond pattern will look nicer without being too complicated.
Using a stone saw or angle grinder, cut any slabs that need to be cut before you start, and make sure you have all of your tools ready to start laying the slabs on mortar. For most patio designs, it is better to start in the middle and work out to the edges.
- Mix up your mortar and lay a bed about 3cm thick for the first slab. It can help the mortar to adhere to the slab if you brush the underside with water a few minutes before you lay it.
- Lay the slab in the mortar and make sure it is sitting firmly with no movement. Place a short length of wood in the middle of the slab as cushioning, and give it a few taps with a lump hammer.
- You can use offcut pieces of timber batten of the required width as spacers between each slab to ensure evenly sized joints. A gap of 10mm between slabs should be plenty.
- Continue to lay slabs in this way, mixing up more mortar as you need it (don’t mix up too much at once until you are confident you can lay slabs reasonably quickly.)
- Use a long spirit level laid across the slabs to check they are following the slight slope you need to help shed water.
- If any slabs are too low or higher than the surrounding slabs, simply lift them up and add or remove some mortar to even them out.
Wait at least 24 hours before walking on any part of the patio. If it looks like it will rain overnight, or if frost is likely, cover the patio with plastic sheeting or tarpaulin. To finish the patio, trowel mortar into the joints and point them using a trowel or brick pointer.