Read this post for comprehensive instructions on how to construct a patio. In this example we’re using sandstone for the slabs. Having a patio area in a garden provides an area to eat, entertain or to simply enjoy the sun. Patio’s come in all shapes and sizes as no job is the same. That’s why it’s so important to consider all the factors that will ensure you get a patio that’s right for you. This guide will help you make the tricky decisions, such as shape, size, location, paving materials and more.
Before you start
Plan ahead and think about the overall size and layout of your patio, plus many more factors. Use the points below to get started:
- Location - Generally speaking, patio’s tend to be situated immediate outside rear doors. However, it's a good idea to situate a patio in an area that gets the most sun, at a time you're most likely to be using it. For example, if you prefer the evening sun whilst relaxing on your patio, then there should be a clear line from the patio towards the West. If you prefer the mornings sun, then ensure there are little obstructions to wards the East. Other factors will affect the location of your patio, such as privacy from neighbours and access from the house.
- Size - The default position of many homeowners is to create the biggest area of paving as possible. Tempting as this may be, have a think about how much patio you will actually need. Being efficient with you paving could allow more in the budget to use more durable, aesthetically pleasing materials that cost more money. If you already have outside furniture, measure them to ensure they can fit on your new patio. If you have a table and chairs, remember to take account of the space required to push the chairs back, and then some more for someone to walk around the chairs. Below is a diagram to illustrate the space required for a small 1.2m diameter round table, as you can see, it requires a surprising amount of space:
- Shape - The shape is usually dictated by the furniture, with paving paths to reach nearby doors. Sometimes it makes sense to stretch the patio to meet existing edges, such as a fenceline, planter or lawn.
- Paving Materials - There are a whole variety of materials to choose from, so much so that we have covered these on separate pages. Briefly, the most common material is sandstone paving slabs, which we have featured on this page. Other materials are limestone, slate, granite, porcelain and many more.
- Patterns - There are a number of different patterns that can be used, you can usually find laying patterns on the paving manufacturers website, so it usually depends on the paving material you’ve chosen. The most common pattern is random, others include stretcher, staggered stretcher, random stretcher, herringbone etc. Again, we cover layng patterns on the individual paving material pages.
- Adjusting the size - Now that you know the paving material, it makes sense to check this against the size and shape of your intended patio, to ensure the number of cuts can be reduced. For instance, if you worked out the shape of your patio to be a simple, square shape measuring 1.75 x 1.75m, then it may make sense to see how this fits with the sizes of the slabs. Slabs are usually 600mm wide, if you include the width of the joints. The lengths vary from 300mm to 1.2m, also including the width of the joints. If we were to lay the paving in a stretcher course, that is with them in rows, then 3 slabs in width would make the patio 1.8m wide, and it may be possible to select the lengths to make 1.8m long. If the room permits, go with this new plan area to avoid unnecessary cuts.
- Drainage - Remember that water will need to drain from your patio to ensure it remains as dry as possible. This will prevent dirt buildup, moss growth and ice in those colder months. It’s a balance, as the gradient should also not be too steep so that the peas roll off your plate when dining outside, but steep enough to shed water effectively. Appropriate gradients can be found elsewhere on our website, but should generally be between 1 in 60 (1.67%) and 1 in 100 (1%). If you can get your patio to fall onto a lawn or flower bed, then there’s no need for any gully’s or channel drains.
- Bucket and hose
- Gloves, dust mask, ear defenders and goggles
- Hand brush
- Mallet or sledgehammer
- Pointing tool
- Rubber mallet
- Spirit levels - large, medium and small if available
- Spray paint
- String lines
- Trowels - large and small
- Wheel barrow
To build your own patio, you'll need:
- Hardcore ( MOT type 1)
- Hessian matting or dust sheets - if laying in winter
- Membrane - porous fabric
- Paving slabs
- Pointing compound or red sand and cement for traditional pointing
- Red sand
- Washed/grit sand
- Wooden Pegs
Method of Constructing a Patio
Choose a place to start, It’s a good idea to think about your access when starting a patio, if your access is an alley down the side of a house then work back from the furthest point, towards the front, so that you don’t block yourself in.
Mark off the area where the new patio is going using spray paint or pegs and string lines, depending on the design. Clear the area of anything that will get in the way, such as rubble, plants or garden furniture. If the patio is to replace grass or flower beds, skim the surface of turf or flowers and any fluffy, aerated topsoil.
Work out the total depth of the patio’s makeup, that is all the layers that will be below the slabs, including the depth of the slabs too. This will be your dig depth and it varies slightly, depending on the thickness of slab used.
Now it’s time to dig down to the formation level of the patio, which is the level at the bottom of the hardcore. To do this, you’ll first need to set up some level reference points, so that you can ensure you don’t dig down too deep. An easy way to do this is to set up a stringline across the patio area, at a predetermined height above the formation level. Don’t forget, you’ll want to lay the patio at a slight fall for drainage, so the formation level should also reflect this fall. For a simple sandstone patio, 1 in 80 will suffice, which means for every 80 units horizontally there’s a 1 unit change in height. For example, If you’re creating a fall across 4m of patio, then you’ll need a fall of 50mm (4m / 80).
Plan where you’re going to position the level pegs. The guide below gives a some good examples. Remember to offset your pegs far enough away from the edge of the paving so that it doesn’t interfere with the dig.
Tie the stringline to one peg, then loosely fasten it to the other peg. To ensure your stringline is level, check the line with your long level. If you need the stringline to be at a fall, first get it level, then adjust the height according to the table above. Once you’ve got all your stringline’s set up, you are now good to dig down to the formation level of the paving, remembering to check against the stringline’s as you go. If you come across any soft spots in the ground, such as disturbed soil where you’ve pulled out a large shrub, remove all loose soil and backfill with hardcore. Compact this hardcore using an inverted sledge hammer or mallet.
Once the area has been dug out, cover the entire area with membrane, this ensures that the hardcore does not mix with the soil over time and stays a strong and firm base for the paving. Overlap pieces of membrane by 100mm (4”).
Next, spread the hardcore over the membrane, again checking against the stringline as you go. Allow for a bit of compaction when spreading the hardcore, so you’ll need to spread it slightly deeper than necessary. For a 75mm thick bed of hardcore, allow an extra 10mm, and 20mm for 150mm deep bed. Hardcore can only be compacted in layers not exceeding 150mm, so if you do need a deeper layer, remember to lay and compact it in layers.
Compaction of the hardcore should be done using a vibratory plate compactor, more commonly known as a whacker plate. These come in many types and sizes. Speak to your local hire depot and they should be able to advise on what they have available. Remember to observe any health and safety precautions when using the plate compactor, such as ear defenders and gloves. Before whacking the hardcore, dampen it down with water using a hose, which helps to keep the dust down and to bind the aggregates together.
Check levels again as the hardcore would have gone down after being whacked, and top up where necessary and compact again until you are within 10mm of the desired level.
The area is now ready to lay your paving, make sure you have decided on your pattern before you start and stack the slabs nearby for easy access. You’ll need to change the height of the stringline, so that they are at the same levels as the finished paving.
Now it’s time to make the bedding mix. Due to the quantity of mortar required, you’ll probably need a cement mixer for this. For example, a very small patio that measures 2m x 2m, with a mortar bed of 40mm will require about 160kg’s of washed/grit sand, 80kg’s red sand and 48kg’s cement to make 0.16m3 of mortar. You’ll be able to get a cement mixer from your local hire depot, observing any health and safety precautions. Before you make your first mix, make sure you have all the tools available to lay the slabs. You’ll also need to get your cement ready. Instead of creating an opening in the top of the bag and trying to shovel out the cement direct from the bag, observe the following instructions to split a bag in half:
Start off by filling the mixer’s drum with water, up to the line where the drum starts to narrow towards the front. Empty a half bag of cement into the mixer and turn the mixer on. Be wary that the mixer will generate a lot of splashing from its drum, so point the mixer away from your house or anything else you don’t want to get splashed with mortar.
Shovel in the desired sand/s. In this example, we’re using a mix of grit/washed sand and red sand. In this example, we’re using a 4:2:1 Washed/grit sand:red sand:cement mix, by volume. Half a bag of cement is two heaped shovels, so we need 8 heaped shovels of washed/grit sand and 4 heaped shovels of red sand. As you shovel in the sand, ensure the mix doesn’t get too dry by topping up with water when necessary. The consistency of the mix is difficult to achieve if you’ve not done this before. It should be wet enough to be workable but it should hold the weight of the slab before being knocked down. The consistency of the mix should be similar to spreadable butter. Whilst it’s turning around in the mixer, the top should flow like a wave but break slightly.
Empty the content into a wheelbarrow, being careful not to splash anything nearby. Using a shovel, put down your mix to create a full bed of mortar that's 15mm below the level of the line. Using a large trowel, flatten off the bed and create grooves in the bedding mix so that the slab can be tampered down.
The first slab is the most difficult to lay because it sets the precedent for the rest of the patio. Take extra care with the first slab, checking it’s in the correct position, laid to the correct fall and orientated correctly. Carefully rest the slab onto the mortar bed, being careful not to drop it. You may need to tuck it under the stringline. With the slab resting on top of the mortar, it should lie about 10mm above the desired level. Use a rubber mallet to tap the slab into place, whilst constantly checking its height against the stringline. You’ll also need to check its gradient against other stringlines by laying a long level on the slab and have it overhang so that it meets another stringline. When tapping the slab into place using a rubber mallet, make sure you don't tap too close to the edge, else this will "pop up" the opposing side of the slab. As this is your first slab, this may take a few times to perfect but if you tap down the slab too much, it’s OK to lift it up, re-shape the mortar bed again and have another go. Once the slab is in place, make sure you clean the mortar off the top of the slab using a bucket of water and a hand brush. To check the slab has been laid correctly, gently try to rock it from corner to corner and if it rocks, you’ll need to lift the slab and try again. Tidy up the sides of the mortar bed, do this using a large trowel and slice off any excess mortar from the sides.
Lay the rest of your slabs in the same manner as above, ensuring that an even 10mm gap is kept between the slabs for the joints. When you create the mortar bed for a slab to be laid next to an existing slab or wall, you’ll need to trowel out extra mortar from that edge, so that the mortar doesn’t squash up when you tap the slab down.
Allow 2 days in warmer months and 3 days in colder months for the mortar to have set sufficiently before walking on the slabs. Your patio will not achieve its full strength until it’s pointed, so only walk on the centre of the slabs when you do so. Also, check the weather forecast, if the temperature is due to drop close to zero overnight, cover the entire patio with hessian matting (available online), or dust sheets. This will protect the mortar from frost damage created when the water is the mortar expands and creates cracks.
Once the slabs have set the last thing to do is point between them. You have two options here, either using jointing compound, which makes light work of the job and means that no staining occurs to the slabs, or a traditional pointing mix of red sand and cement.
Jointing compound comes in many colours and types. It is a manufactured product that is designed to be brushed into the joint, without the need, in many cases, for time consuming joint compaction. You should always adhere to the manufacturer's instructions when applying jointing compound. Generally, you need to dowse the slabs first with water, pour the compound into the joints and allow to settle, brush in more compound into the joints and finish off by brushing away any excess. Compound can usually be laid in dry and moderately wet weather, and does not require completely dry conditions whilst it sets. It can be expensive stuff, at anything from £30-£50 per tub to cover 7-10m2 of paving, but can save considerable time.
A traditional jointing mix is and mixed to a 3:1 ratio of red sand:cement. To prevent staining of the slabs, this can only be carried out when the slabs are dry, and there’s no chance of rain for at least 24 hours. Dry mix the sand and cement first in a bucket, so that the red sand turns lighter in colour and it’s free from lumps. Only mix about an eighth of a bucket at any time. Then add very small amounts of water at a time, whilst consistently mixing using a small trowel. The consistency should be that of dry breadcrumbs and not sticky, so that the mix doesn’t leach into the slabs and stain them. If it ends up too wet, simply add more sand and cement at the right proportions until the moisture content is brought down. Grab your trowel, bucket, dry hand brush and pointing tool and go to where you plan to start pointing, remembering to work backwards and standing only on the centre of the slabs. Trowel out the pointing mix to fill the joints, then lightly compact the mix into the joints using the pointing tool. Don’t compact the joints too firmly, at the same time you need to ensure the joints are completely filled. When the joints are filled, you shouldn’t be able to compress the pointing mix with moderate finger pressure, but it should leave the imprint of your fingerprint. Smooth off the surface in the shape of your desire, as shown below. Remember to brush away any excess pointing mix using a soft brush and cover the slabs if there’s going to be some cold weather. Allow the pointing to dry for a couple of days before washing down the patio.