laying a patio - a step by step guide

Introduction

 This page is designed to teach you how to lay a basic garden patio in easy steps.  We are approaching the patio project as beginners having never laid one before. Although it can be hard physical work there is no reason why anyone with moderate DIY skills shouldn't attempt to lay their own simple garden patio

A garden patio can be as simple or as complex as you choose, this guide is for a simple patio laid with regular shaped concrete flagstones.

My finished patio

Gravel margins allow for small measuring errors as well as preventing splashback from rain making your wall damp
Gravel margins allow for small measuring errors as well as preventing splashback from rain making your wall damp

Step 1 - Planning

 Yes I know it's a bit dull when you really want to get started on a project but time spent now really will make life easier and the project run more smoothly and cost efficiently in the long run.  Things to think about include:

  • Which way will the patio slope?  Of course you don't want an obviously sloping patio but you do need a shallow regular slope to allow surface water run off away from the house. A slope of 16mm/metre ( or 5/8" per yard) should be adequate
  • What level are you working to on your brickwork?  Flagstones should be laid at least 150mm (6") below the damp proof course of your house, as there will be splash back from rain against the brickwork of the house. 
  • Plan for a 100mm margin of gravel between the wall and flagstones.  This helps drainage of surface water as well as giving you a little bit of margin of error with your measurements.  If you wanted you could plant  a climbing plant in this border.
  • Plan your area so that you can minimise (or hopefully eliminate) the need to cut flagstones
  • What sort of base do you need.  For the simple garden patio a base of 35mm of sharp sand should be adequate on top of compacted soil.  A peaty or clay soil may require you  to lay a hardcore layer (rough gravel/stone/broken brick) of 75mm below the sand. Although  we're not really covering it here if you were to be laying a patio for heavier loads you would also want this hardcore layer.
  • What sort of flagstone will you use? Larger lagstones are harder to handle but you need to lay less making getting your levels or slope easier.  Regular square or rectangles are easier to plan and will require less cutting. Standard thickness for a graden patio is approx 30-40mm, more heavy duty 50mm flagstone are available for weight bearing patios but are more costly and significantly heavier to handle.  If you are doing it by yourself don't consider larger than 600x600mm (2'x2') of the 30-40mm variety

Preparing the base

  1.  Clear the surface vegetation and topsoil, excavating ot a depth of; flagstone thickness + 35mm /1.5" for the sharp sand layer (+hardcore layer if required).  It's a good idea to lay any flagstones a couple of centimetres below the level of any surrounding grass to prevent damage to your lawnmower.
  2. Cut some wooden pegs with markings for the different layers as above.  It's a good idea to notch these with a saw at these levels i.e. the level of the base of the flagstone/top of sand layer and level of the bottom of the sand layer.  The top of the peg is where the top of the flagstone will be level with
  3. Drive these pegs into the ground to mark the boundary of the patio and using the notches, run some string between them at the lowest layer.
  4. Using a long piece of wood as a straight edge, place this over the top of the pegs, then place your spirit level on top of this piece of wood to ensure you've got the levels correct.  Don't forget to allow for a slope to allow water runoff.  (To be precise you could cut a piece of wood to the thickness of the total fall across the slope, place this on top of the lowest peg and using your spirit level adjust the depths of the pegs so that the straight edge is level)
  5.   Level the soil to the level of the string using a rake and compact it (using a graden roller is the easiest way to do this).
  6. Now move the string to the higher notch on your peg and level the sand to this level.  Tamp the sand down using a piece of wood with a straight edge

Laying the Flagstones

Use spacers between the flagstone to keep joint equal and straight
Use spacers between the flagstone to keep joint equal and straight
Using an angle grinder cut around any obstacle that you can't move
Using an angle grinder cut around any obstacle that you can't move
Patio before joints are filled
Patio before joints are filled

Laying the flagstones

  1.  Lay the edge flagstones on top of the sand in both directions from a corner.  Now is a good time to double check all measurements!  Is the level right? Is the fall correct?  Use your straight edge to check these.  Don't get too stressed yet, it needs to be close to right but not yet perfect!
  2. Use spacers between the flagstones to ensure joints are straight and equal (you need at least 2 spacers along each edge)
  3. Once you are satisfied with the position of these edge slabs lift them one at a time and put 5 fist sized blobs of mortar under each flagstone, one at each corner and a fifth in the centre and lay them down again on top of this.  (weight bearing patios should be laid on a solid layer of mortar)
  4. Using a large hammer on a thick piece of wood to protect the surface of the flagstone tap the flagstone to return it to the level you want.  This is where you need to get the levels spot on.  This is the slow part and it can be frustrating as you may need to lift the flagtone and re lay it if it is rocking or too high or low in one area and you can't solve it with your hammer!
  5. Once you are happy with these flagstones lay the remainder of the flagstones working from those already laid, all the time using your spacers
  6. If you have any obstacles next to the wall eg drains or waste pipes you may need to cut around them using and angle grinder.  I hired a Makita angle grinder from my local hire shop for £15 and had to buy a stone blade for £3.  Diamond blades can be hired but are really only worth it if you have to cut a lot of flagstones, my hire shop charge £20 to hire plus a charge for the amount of blade you use.
  7. Remove the spacers before the mortar dries. Leave the joints empty for two days to allow the mortar to dry and don't walk on the flagstones during this time.

Filling the Joints

Pour dry mortar into the joints
Pour dry mortar into the joints
Brush the mortar into the joint
Brush the mortar into the joint
Joints after dry mortaring
Joints after dry mortaring

 Fill the joints with a dry mortar mix as shown above.  Once you are happy with this use a watering can with a fine spray head to water over the joints and leave to dry.

Use a mortar mix to fill any gaps around drains or waste pipes if necessary.

 

Once all the mortar is dry, get your deckchair out, open a beer and relax, you've earned it!

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