Date:31 January 2017
When my wife and I left our tiny one-bedroom apartment for a new place a little further from the CBD, we were thrilled by a lot of things. Like central heating and air, a spare bedroom, and enough space to have an actual kitchen table, just like real adults. But what we were most excited for was the backyard. Our new backyard is not a nice backyard. It’s small, 6 by 5 metres. There’s not even grass, just a concrete floor with a drain in the centre. All there really is, is opportunity – and soon there will be a patio.
By: Peter Martin
For us, a patio provides a place to grill and to host the dinner parties my wife insists she gets pleasure out of throwing. And I definitely plan on falling asleep out there on Saturday mornings, when it’s too late to be in bed, but too early for TV sport. For you, it may be a place for sunrise breakfasts or a kiddie pool or the perfect spot to set up what people on Pinterest call a bistro table.
However you plan on using a patio, you need to choose the right material to build it. Concrete is durable and long-lasting, and brick is attractive, but the best option we’ve found is bluestone (natural rock options for South Africans include slate).
Designed by Roy Berendsohn
Choose the dimensions for your patio, then mark them off by driving batter boards (H-shaped stakes) between a half and one metre outside the corners of the four boundaries. You want them far enough away from the perimeter that you won’t need to move anything during construction. Stretch mason’s string between the stakes to mark the edges of the patio. Clip a line level to the mason’s string to ensure an accurate horizontal reference.
Use a spade to create the perimeter of yourhole. Cutthe hole 20 centimetres deep – enough to accommodate the layers of support beneath the stones and the stones themselves. The sides should be clean and square. Check the bottom of the hole for level with a 1,2-metre level. If you don’t have one, you can place a smaller level on top of a long straight piece of planking to get the same effect. Backfill any areas that were cut too deep and use a hand compactor to firmly pack them. It’s very important that each layer of your patio be level. Any shallow spots can cause water to pool, creating puddles.
The next step is to add base material, usually crushed stone or gravel. Unlike soil, stone has a uniform hardness and provides efficient drainage. But before you can add that, you need to set up your screeds – straight planks set parallel in the hole – about a metre apart. Posts about 50 by 100 mm positioned on edge work well. Sight down each to make sure that the boards are straight and do not crown, or rise up, in the middle; then check them for level in the hole. If your screeds aren’t long enough to span the patio space, or if you don’t have enough to cover the entire area at once, work in segments.
Set your screeds in the footprint of your patio. Hold them in place by packing base material around their sides. Then dump three to five centimetres of base layer between the screeds. (Each layer is called a lift.) Distribute the stone with a base rake, a wide aluminium plate with one smooth and one serrated edge.
An ordinary bow rake will also work, but you’ll need to rake several passes with the tines down, then flip the rake on its back for a few more passes.
Cut a piece of timber to fit from one screed to the other, notching it, if necessary, to fit between them. This is called a screed board. Slide it over the material to level its surface.
Each lift needs to be compacted before the next is laid. After adding the first layer, remove the screeds and fill in the slots left behind with base material. Using a powered vibrating compactor, which you can rent, start on the outside of your patio footprint and make a single lap around the perimeter. Then move in towards the centre in concentric rings, overlapping each pass by half the width of the compactor’s base plate. One round of this should be enough. You’ll know it’s properly compacted if you can step on the material and it doesn’t take a footprint.
Reset your screeds and add another layer of base material, up to five centimetres thick. Remove the screeds, fill the remaining gaps and compact again.
The next lift is the bedding layer, which can be anything from finer crushed stone to sand. This layer provides a softer surface for the stones to settle into. Place your screeds over the base layer. Then add around five centimetres of bedding. After you’ve screeded the bedding layer, mist it with a fine spray from a garden hose. The water lubricates the stone or sand particles in the bedding and allows a firmer pack. Remove the screeds, fill the leftover slots and compact the bedding layer.
Start at one corner and run the first row of stones on the bedding, as close to each other as possible. Given that the face of the stone against the bedding is relatively uneven and the stone’s thickness varies, to avoid wobbles you’ll need to level each one by making slight adjustments to the bedding material. Use a concrete float to smooth the bedding material after making those adjustments, and tap each stone level with a dead-blow mallet. An easy way to check for level is to lower your string line so it sits a little bit above the stones – the thickness of a scrap of timber. Now you can slide the wood across the stones, and if it fits perfectly between the line and the stone, you know your patio is level.
If you need to cut any stones for fit, do it with a circular saw and a diamond-grit masonry blade. If you find yourself doing a lot of cutting, you can always rent a petrol-engine power cutter. Whichever method you choose, use a spray bottle to mist water on the blade to reduce dust.
Use a large exterior broom to sweep bedding material over the surface of the patio to fill in the joints. After the surface has been thoroughly swept in, mist it with a garden hose to consolidate the material.
A garden edger is a useful tool for packing the material between joints. It’s just the right width and lets you remain standing as you pack. Repeat the process until the joints are completely filled and packed.
This article was originally published in the November 2016 issue of Popular Mechanics.