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Laying a Patio

By: Chris Hogan MSc - Updated: 4 Dec 2012 | comments*Discuss
 
Concrete Patio Paving Diy Slabs Spirit

Patios and other hard landscaping areas around the house are a popular addition to a garden. They provide a surface for tables and chairs and help to make the garden more usable, an extension of the house.

As this site is aimed at basic DIY skills we'll be looking at a simple patio made of square paving slabs. But there is a huge variety of different materials and finishes to choose from, so if this looks simple enough once you've read through it, consider something more ambitious.

Planning Your Patio

Decide where you want the patio and mark the area with stout string and pegs. The patio should start at least six inches below any damp-proof course and slope gently away from the house (this is known as 'the fall') to encourage drainage. The slope should be about 1 in 100, or roughly half an inch down for every one-and-a-half yards along. So tie the string slightly lower on the pegs as you move away from the house.

It's recommended to leave a two or three inch gap between the house and the patio and fill it with gravel once you are finished. This will prevent rain splashing up onto the house wall. Plan your layout starting from the house and move outward, adjusting the size to fit the paving slabs so that cutting is minimised.

Excavation

Now it's time to dig out. Remove turf and dig out plants and weeds, then take away topsoil until you have a roughly level area about six inches deep. There's a lot of differing advice as to whether you need a hardcore sub-layer beneath the concrete. The truth is that it depends on the ground conditions in your garden.

If it's very wet or unstable then you should put down small grade hardcore then compact and level it with the edge of a thick plank. But if the ground is firm and dry then there is no need, just level and compact the earth. There's also little need for a weed-proof membrane, any weeds that can damage properly laid paving slabs aren't going to be stopped by a weed membrane.

Different Cement Laying Methods

The paving slabs will be laid down on cement and there are two main ways of doing this. The way most often recommended as being easier for DIY beginners, is known as 'dot and dab. This is where five spots of cement are laid down, one in the middle of each slab and one in each corner. This provides reasonable support for a lightly trafficked patio area.

However this leaves cavities under each slab that can be undermined by water pooling and draining, and insect life burrowing away. Also the 'dabs' can settle differently as they cure, causing the paving slabs to rock and eventually break.

Few professionals would use this method, they would lay a bed of concrete and then place slabs on top of that, and that's the method we'll follow here. Make up a semi-dry mix with one part cement to six parts of coarse grit sand, don't use building sand as it's too soft. For more information about how to mix cement and the various combinations, see our separate article in this section.

Placing Paving Slabs

Spread the mix evenly over the area, you're looking to get a layer about three inches thick, a little more if you've had to put down a layer of hardcore. Place each paving stone, working outward from the house. Tap corners with a rubber mallet to level the slab, checking with a long spirit level.

A good tip is to set up a plank at the required fall and put your spirit level on it, marking with tape or a marker pen the point the end of the bubble reaches. Then you can use the spirit level to gauge the fall. Leave a gap about half an inch between each slab and try to keep it uniform.

When you have to go around obstructions like drain covers cut blocks with an angle grinder which you can hire for the day. Or use a hammer and a cold chisel or bolster, which is cheaper in the short term but probably more expensive in the long term, after you've had to throw a way a few paving slabs. You should be wearing gloves, eye protection and a mask while doing this, of course, as is the case with any DIY job like this.

Mortar for the Joints

Once you are done you can put mortar in the joints.. There are many different ways to mortar a patio but we will use dry jointing. This is probably the easiest and sufficient for a small patio next to a house. Wait for a couple of days for the paving slabs to set and don't put any weight on the patio.

Then, on a dry day when the patio is also dry, mix one part cement with one part sand but no water. Then sprinkle it onto the joints, brushing it in and tapping gently to make sure the mix sinks down properly. Go over the patio as many times as necessary until all the joints are full and level. Then sweep off any excess and leave it for another day or so.

Over time the mortar mix will set, using the moisture from the air and rainfall. This slow setting makes the joint more flexible in the future so hopefully you can enjoy the fruits of your labour for years to come.

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